tobi/M7350
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

M7350v1_en_gpl

Browse Source
This commit is contained in:
T
2024-09-09 08:52:07 +00:00
commit f9cc65cfda
65988 changed files with 26357421 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

566
base/docs/html/guide/tutorials/hello-world.jd Normal file
View File

@ -0,0 +1,566 @@
page.title=Hello, World
@jd:body
<div id="qv-wrapper">
<div id="qv">
<h2>In this document</h2>
<ol>
<li><a href="#avd">Create an AVD</a></li>
<li><a href="#create">Create the Project</a></li>
<li><a href="#ui">Construct the UI</a></li>
<li><a href="#run">Run the Code</a></li>
<li><a href="#upgrading">Upgrade the UI to an XML Layout</a></li>
<li><a href="#debugging">Debug Your Project</a></li>
<li><a href="#noeclipse">Creating the Project Without Eclipse</a></li>
</ol>
</div>
</div>
<p>As a developer, you know that the first impression
of a development framework is how easy it is to write "Hello,
World." Well, on Android, it's pretty easy.
It's particularly easy if you're using Eclipse as your IDE, because we've provided a
great plugin that handles your project creation and management to greatly speed-up your
development cycles.</p>
<p>If you're not using Eclipse, that's okay. Familiarize yourself with
<a href="{@docRoot}guide/developing/other-ide.html">Developing in Other IDEs</a>.
You can then return to this tutorial and ignore anything about Eclipse.</p>
<p>Before you start, you should already have the very latest SDK installed, and if you're using
Eclipse, you should have installed the ADT plugin as well. If you have not installed these, see
<a href="{@docRoot}sdk/installing.html">Installing the Android SDK</a> and return
here when you've completed the installation.</p>
<h2 id="avd">Create an AVD</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<p>To learn more about how to use AVDs and the options
available to you, refer to the
<a href="{@docRoot}guide/developing/tools/avd.html">Android
Virtual Devices</a> document.</p>
</div>
</div>
<p>In this tutorial, you will run your application in the Android Emulator.
Before you can launch the emulator, you must create an
Android Virtual Device (AVD). An AVD defines the system image and
device settings used by the emulator.</p>
<p>To create an AVD, use the "android" tool provided in the Android SDK.
Open a command prompt or terminal, navigate to the
<code>tools/</code> directory in the SDK package and execute:
<pre>
android create avd --target 2 --name my_avd
</pre>
<p>The tool now asks if you would like to create a custom hardware profile.
For the time being, press Return to skip it ("no" is the default response).
That's it. This configures an AVD named "my_avd" that uses the Android 1.5
platform. The AVD is now ready for use in the emulator.</p>
<p>In the above command, the <code>--target</code> option is required
and specifies the deployment target to run on the emulator.
The <code>--name</code> option is also required and defines the
name for the new AVD.</p>
<h2 id="create">Create a New Android Project</h2>
<p>After you've created an AVD, the next step is to start a new
Android project in Eclipse.</p>
<ol>
<li>From Eclipse, select <strong>File &gt; New &gt; Project</strong>.
<p>If the ADT
Plugin for Eclipse has been successfully installed, the resulting dialog
should have a folder labeled "Android" which should contain
"Android Project". (After you create one or more Android projects, an entry for
"Android XML File" will also be available.)</p>
</li>
<li>Select "Android Project" and click <strong>Next</strong>.<br/>
<a href="images/hello_world_0.png"><img src="images/hello_world_0.png" style="height:230px" alt="" /></a>
</li>
<li>Fill in the project details with the following values:
<ul>
<li><em>Project name:</em> HelloAndroid</li>
<li><em>Application name:</em> Hello, Android</li>
<li><em>Package name:</em> com.example.helloandroid (or your own private namespace)</li>
<li><em>Create Activity:</em> HelloAndroid</li>
<li><em>Min SDK Version:</em> 2</li>
</ul>
<p>Click <strong>Finish</strong>.</p>
<a href="images/hello_world_1.png"><img src="images/hello_world_1.png" style="height:230px" alt="" /></a>
<p>Here is a description of each field:</p>
<dl>
<dt><em>Project Name</em></dt>
<dd>This is the Eclipse Project name &mdash; the name of the directory
that will contain the project files.</dd>
<dt><em>Application Name</em></dt>
<dd>This is the human-readable title for your application &mdash; the name that
will appear on the Android device.</dd>
<dt><em>Package Name</em></dt>
<dd>This is the package namespace (following the same rules as for
packages in the Java programming language) that you want all your source code to
reside under. This also sets the package name under which the stub
Activity will be generated.
<p>Your package name must be unique across
all packages installed on the Android system; for this reason, it's very
important to use a standard domain-style package for your
applications. The example above uses the "com.example" namespace, which is
a namespace reserved for example documentation &mdash;
when you develop your own applications, you should use a namespace that's
appropriate to your organization or entity.</p></dd>
<dt><em>Create Activity</em></dt>
<dd>This is the name for the class stub that will be generated by the plugin.
This will be a subclass of Android's {@link android.app.Activity} class. An
Activity is simply a class that can run and do work. It can create a UI if it
chooses, but it doesn't need to. As the checkbox suggests, this is optional, but an
Activity is almost always used as the basis for an application.</dd>
<dt><em>Min SDK Version</em></dt>
<dd>This value specifies the minimum API Level required by your application. If the API Level
entered here matches the API Level provided by one of the available targets,
then that Build Target will be automatically selected (in this case, entering
"2" as the API Level will select the Android 1.1 target). With each new
version of the Android system image and Android SDK, there have likely been
additions or changes made to the APIs. When this occurs, a new API Level is assigned
to the system image to regulate which applications are allowed to be run. If an
application requires an API Level that is <em>higher</em> than the level supported
by the device, then the application will not be installed.</dd>
</dl>
<p><em>Other fields</em>: The checkbox for "Use default location" allows you to change
the location on disk where the project's files will be generated and stored. "Build Target"
is the platform target that your application will be compiled against
(this should be selected automatically, based on your Min SDK Version).</p>
<p class="note">Notice that the "Build Target" you've selected uses the Android 1.1
platform. This means that your application will be compiled against the Android 1.1
platform library. If you recall, the AVD created above runs on the Android 1.5 platform.
These don't have to match; Android applications are forward-compatible, so an application
built against the 1.1 platform library will run normally on the 1.5 platform. The reverse
is not true.</p>
</li>
</ol>
<p>Your Android project is now ready. It should be visible in the Package
Explorer on the left.
Open the <code>HelloAndroid.java</code> file, located inside <em>HelloAndroid > src >
com.example.helloandroid</em>). It should look like this:</p>
<pre>
package com.example.helloandroid;
import android.app.Activity;
import android.os.Bundle;
public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}</pre>
<p>Notice that the class is based on the {@link android.app.Activity} class. An Activity is a
single application entity that is used to perform actions. An application may have many separate
activities, but the user interacts with them one at a time. The
{@link android.app.Activity#onCreate(Bundle) onCreate()} method
will be called by the Android system when your Activity starts &mdash;
it is where you should perform all initialization and UI setup. An activity is not required to
have a user interface, but usually will.</p>
<p>Now let's modify some code! </p>
<h2 id="ui">Construct the UI</h2>
<p>Take a look at the revised code below and then make the same changes to your HelloAndroid class.
The bold items are lines that have been added.</p>
<pre>
package com.android.helloandroid;
import android.app.Activity;
import android.os.Bundle;
<strong>import android.widget.TextView;</strong>
public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
<strong>TextView tv = new TextView(this);
tv.setText(&quot;Hello, Android&quot;);
setContentView(tv);</strong>
}
}</pre>
<p class="note"><strong>Tip:</strong> An easy way to add import packages to your project is
to press <strong>Ctrl-Shift-O</strong> (<strong>Cmd-Shift-O</strong>, on Mac). This is an Eclipse
shortcut that identifies missing packages based on your code and adds them for you.</p>
<p>An Android user interface is composed of hierarchies of objects called
Views. A {@link android.view.View} is a drawable object used as an element in your UI layout,
such as a button, image, or (in this case) a text label. Each of these objects is a subclass
of the View class and the subclass that handles text is {@link android.widget.TextView}.</p>
<p>In this change, you create a TextView with the class constructor, which accepts
an Android {@link android.content.Context} instance as its parameter. A
Context is a handle to the system; it provides services like
resolving resources, obtaining access to databases and preferences, and so
on. The Activity class inherits from Context, and because your
HelloAndroid class is a subclass of Activity, it is also a Context. So, you can
pass <code>this</code> as your Context reference to the TextView.</p>
<p>Next, you define the text content with
{@link android.widget.TextView setText(CharSequence) setText()}.</p>
<p>Finally, you pass the TextView to
{@link android.app.Activity#setContentView(View) setContentView()} in order to
display it as the content for the Activity UI. If your Activity doesn't
call this method, then no UI is present and the system will display a blank
screen.</p>
<p>There it is &mdash; "Hello, World" in Android! The next step, of course, is
to see it running.</p>
<h2 id="run">Run the Application</h2>
<p>The Eclipse plugin makes it very easy to run your applications:</p>
<ol>
<li>Select <strong>Run > Run</strong>.</li>
<li>Select "Android Application".</li>
</ol>
<div class="sidebox-wrapper">
<div class="sidebox">
<p>To learn more about creating and editing run configurations in Eclipse, refer to
<a href="{@docRoot}guide/developing/eclipse-adt.html#RunConfig">Developing In Eclipse,
with ADT</a>.</p>
</div>
</div>
<p>The Eclipse ADT will automatically create a new run configuration for your project
and the Android Emulator will automatically launch. Once the emulator is booted up,
your application will appear after a moment. You should now see something like this:</p>
<a href="images/hello_world_5.png"><img src="images/hello_world_5.png" style="height:230px" alt="" /></a>
<p>The "Hello, Android" you see in the grey bar is actually the application title. The Eclipse plugin
creates this automatically (the string is defined in the <code>res/values/strings.xml</code> file and referenced
by your <code>AndroidManifest.xml</code> file). The text below the title is the actual text that you have
created in the TextView object.</p>
<p>That concludes the basic "Hello World" tutorial, but you should continue reading for some more
valuable information about developing Android applications.</p>
<h2 id="upgrading">Upgrade the UI to an XML Layout</h2>
<p>The "Hello, World" example you just completed uses what is called a "programmatic"
UI layout. This means that you constructed and built your application's UI
directly in source code. If you've done much UI programming, you're
probably familiar with how brittle that approach can sometimes be: small
changes in layout can result in big source-code headaches. It's also very
easy to forget to properly connect Views together, which can result in errors in
your layout and wasted time debugging your code.</p>
<p>That's why Android provides an alternate UI construction model: XML-based
layout files. The easiest way to explain this concept is to show an
example. Here's an XML layout file that is identical in behavior to the
programmatically-constructed example:</p>
<pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;TextView xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
android:layout_width=&quot;fill_parent&quot;
android:layout_height=&quot;fill_parent&quot;
android:text=&quot;@string/hello&quot;/&gt;</pre>
<p>The general structure of an Android XML layout file is simple: it's a tree
of XML elements, wherein each node is the name of a View class
(this example, however, is just one View element). You can use the
name of any class that extends {@link android.view.View} as an element in your XML layouts,
including custom View classes you define in your own code. This
structure makes it very easy to quickly build up UIs, using a more simple
structure and syntax than you would use in a programmatic layout. This model is inspired
by the web development model, wherein you can separate the presentation of your
application (its UI) from the application logic used to fetch and fill in data.</p>
<p>In the above XML example, there's just one View element: the <code>TextView</code>,
which has four XML attributes. Here's a summary of what they mean:</p>
<table>
<tbody>
<tr>
<th>
Attribute
</th>
<th>
Meaning
</th>
</tr>
<tr>
<td>
<code>xmlns:android</code>
</td>
<td>
This is an XML namespace declaration that tells the Android tools that you are going to refer to common attributes defined in the Android namespace. The outermost tag in every Android layout file must have this attribute.<br>
</td>
</tr>
<tr>
<td>
<code>android:layout_width</code>
</td>
<td>
This attribute defines how much of the available width on the screen this View should consume.
In this case, it's the only View so you want it to take up the entire screen, which is what a value of "fill_parent" means.<br>
</td>
</tr>
<tr>
<td>
<code>android:layout_height</code>
</td>
<td>
This is just like android:layout_width, except that it refers to available screen height.
</td>
</tr>
<tr>
<td>
<code>android:text</code>
</td>
<td>
This sets the text that the TextView should display. In this example, you use a string
resource instead of a hard-coded string value.
The <em>hello</em> string is defined in the <em>res/values/strings.xml</em> file. This is the
recommended practice for inserting strings to your application, because it makes the localization
of your application to other languages graceful, without need to hard-code changes to the layout file.
For more information, see <a href="{@docRoot}guide/topics/resources/resources-i18n.html">Resources
and Internationalization</a>.
</td>
</tr>
</tbody>
</table>
<p>These XML layout files belong in the <code>res/layout/</code> directory of your project. The "res" is
short for "resources" and the directory contains all the non-code assets that
your application requires. In addition to layout files, resources also include assets
such as images, sounds, and localized strings.</p>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Landscape layout</h2>
<p>When you want a different design for landscape, put your layout XML file
inside /res/layout-land. Android will automatically look here when the layout changes.
Without this special landscape layout defined, Android will stretch the default layout.</p>
</div>
</div>
<p>The Eclipse plugin automatically creates one of these layout files for you: main.xml.
In the "Hello World" application you just completed, this file was ignored and you created a
layout programmatically. This was meant to teach you more
about the Android framework, but you should almost always define your layout
in an XML file instead of in your code.
The following procedures will instruct you how to change your
existing application to use an XML layout.</p>
<ol>
<li>In the Eclipse Package Explorer, expand the
<code>/res/layout/</code> folder and open <code>main.xml</code> (once opened, you might need to click
the "main.xml" tab at the bottom of the window to see the XML source). Replace the contents with
the following XML:
<pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;TextView xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
android:layout_width=&quot;fill_parent&quot;
android:layout_height=&quot;fill_parent&quot;
android:text=&quot;@string/hello&quot;/&gt;</pre>
<p>Save the file.</p>
</li>
<li>Inside the <code>res/values/</code> folder, open <code>strings.xml</code>.
This is where you should save all default text strings for your user interface. If you're using Eclipse, then
ADT will have started you with two strings, <em>hello</em> and <em>app_name</em>.
Revise <em>hello</em> to something else. Perhaps "Hello, Android! I am a string resource!"
The entire file should now look like this:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;resources>
&lt;string name="hello">Hello, Android! I am a string resource!&lt;/string>
&lt;string name="app_name">Hello, Android&lt;/string>
&lt;/resources>
</pre>
</li>
<li>Now open and modify your <code>HelloAndroid</code> class use the
XML layout. Edit the file to look like this:
<pre>
package com.example.helloandroid;
import android.app.Activity;
import android.os.Bundle;
public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}</pre>
<p>When you make this change, type it by hand to try the
code-completion feature. As you begin typing "R.layout.main" the plugin will offer you
suggestions. You'll find that it helps in a lot of situations.</p>
<p>Instead of passing <code>setContentView()</code> a View object, you give it a reference
to the layout resource.
The resource is identified as <code>R.layout.main</code>, which is actually a compiled object representation of
the layout defined in <code>/res/layout/main.xml</code>. The Eclipse plugin automatically creates this reference for
you inside the project's R.java class. If you're not using Eclipse, then the R.java class will be generated for you
when you run Ant to build the application. (More about the R class in a moment.)</p>
</li>
</ol>
<p>Now re-run your application &mdash; because you've created a launch configuration, all
you need to do is click the green arrow icon to run, or select
<strong>Run &gt; Run History &gt; Android Activity</strong>. Other than the change to the TextView
string, the application looks the same. After all, the point was to show that the two different
layout approaches produce identical results.</p>
<p class="note"><strong>Tip:</strong> Use the shortcut <strong>Ctrl-F11</strong>
(<strong>Cmd-Shift-F11</strong>, on Mac) to run your currently visible application.</p>
<p>Continue reading for an introduction
to debugging and a little more information on using other IDEs. When you're ready to learn more,
read <a href="{@docRoot}guide/topics/fundamentals.html">Application
Fundamentals</a> for an introduction to all the elements that make Android applications work.
Also refer to the <a href="{@docRoot}guide/index.html">Developer's Guide</a>
introduction page for an overview of the <em>Dev Guide</em> documentation.</p>
<div class="special">
<h3>R class</h3>
<p>In Eclipse, open the file named <code>R.java</code> (in the <code>gen/</code> [Generated Java Files] folder).
It should look something like this:</p>
<pre>
package com.example.helloandroid;
public final class R {
public static final class attr {
}
public static final class drawable {
public static final int icon=0x7f020000;
}
public static final class layout {
public static final int main=0x7f030000;
}
public static final class string {
public static final int app_name=0x7f040001;
public static final int hello=0x7f040000;
}
}
</pre>
<p>A project's <code>R.java</code> file is an index into all the resources defined in the
file. You use this class in your source code as a sort of short-hand
way to refer to resources you've included in your project. This is
particularly powerful with the code-completion features of IDEs like Eclipse
because it lets you quickly and interactively locate the specific reference
you're looking for.</p>
<p>It's possible yours looks slighly different than this (perhaps the hexadecimal values are different).
For now, notice the inner class named "layout", and its
member field "main". The Eclipse plugin noticed the XML
layout file named main.xml and generated a class for it here. As you add other
resources to your project (such as strings in the <code>res/values/string.xml</code> file or drawables inside
the <code>res/drawable/</code> direcory) you'll see <code>R.java</code> change to keep up.</p>
<p>When not using Eclipse, this class file will be generated for you at build time (with the Ant tool).</p>
<p><em>You should never edit this file by hand.</em></p>
</div>
<h2 id="debugging">Debug Your Project</h2>
<p>The Android Plugin for Eclipse also has excellent integration with the Eclipse
debugger. To demonstrate this, introduce a bug into
your code. Change your HelloAndroid source code to look like this:</p>
<pre>
package com.android.helloandroid;
import android.app.Activity;
import android.os.Bundle;
public class HelloAndroid extends Activity {
/** Called when the activity is first created. */
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Object o = null;
o.toString();
setContentView(R.layout.main);
}
}</pre>
<p>This change simply introduces a NullPointerException into your code. If
you run your application again, you'll eventually see this:</p>
<a href="images/hello_world_8.png"><img src="images/hello_world_8.png" style="height:230px" alt="" /></a>
<p>Press "Force Quit" to terminate the application and close the emulator window.</p>
<p>To find out more about the error, set a breakpoint in your source code
on the line <code>Object o = null;</code> (double-click on the marker bar next to the source code line). Then select <strong>Run &gt; Debug History &gt; Hello,
Android</strong> from the menu to enter debug mode. Your app will restart in the
emulator, but this time it will suspend when it reaches the breakpoint you
set. You can then step through the code in Eclipse's Debug Perspective,
just as you would for any other application.</p>
<a href="images/hello_world_9.png"><img src="images/hello_world_9.png" style="height:230px" alt="" /></a>
<h2 id="noeclipse">Creating the Project without Eclipse</h2>
<p>If you don't use Eclipse (such as if you prefer another IDE, or simply use text
editors and command line tools) then the Eclipse plugin can't help you.
Don't worry though &mdash; you don't lose any functionality just because you don't
use Eclipse.</p>
<p>The Android Plugin for Eclipse is really just a wrapper around a set of tools
included with the Android SDK. (These tools, like the emulator, aapt, adb,
ddms, and others are <a href="{@docRoot}guide/developing/tools/index.html">documented elsewhere.</a>)
Thus, it's possible to
wrap those tools with another tool, such as an 'ant' build file.</p>
<p>The Android SDK includes a tool named "android" that can be
used to create all the source code and directory stubs for your project, as well
as an ant-compatible <code>build.xml</code> file. This allows you to build your project
from the command line, or integrate it with the IDE of your choice.</p>
<p>For example, to create a HelloAndroid project similar to the one created
in Eclipse, use this command:</p>
<pre>
android create project \
--package com.android.helloandroid \
--activity HelloAndroid \
--target 2 \
--path <em>&lt;path-to-your-project></em>/HelloAndroid
</pre>
<p>This creates the required folders and files for the project at the location
defined by the <em>path</em>.</p>
<p>For more information on how to use the SDK tools to create and build projects, please read
<a href="{@docRoot}guide/developing/other-ide.html">Developing in Other IDEs</a>.</p>

BIN
base/docs/html/guide/tutorials/images/hello_world_0.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 6.2 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_1.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 9.8 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_2.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 11 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_3.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 11 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_4.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 60 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_5.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 6.1 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_8.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 11 KiB

BIN
base/docs/html/guide/tutorials/images/hello_world_9.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 6.6 KiB

8
base/docs/html/guide/tutorials/index.html Normal file
View File

@ -0,0 +1,8 @@
<html>
<head>
<meta http-equiv="refresh" content="0;url=../index.html">
</head>
<body>
<a href="../index.html">click here</a> if you are not redirected.
</body>
</html>

593
base/docs/html/guide/tutorials/localization/index.jd Executable file
View File

@ -0,0 +1,593 @@
page.title=Hello, L10N
@jd:body
<div id="qv-wrapper">
<div id="qv">
<h2>In this document</h2>
<ol>
<li><a href="#unlocalized">Create an Unlocalized App</a>
<ol>
<li><a href="#create">Create the Project and Layout</a></li>
<li><a href="#default">Create Default Resources</a></li>
</ol>
</li>
<li><a href="#run">Run the Unlocalized App</a></li>
<li><a href="#plan">Plan the Localization</a></li>
<li><a href="#localize">Localize the App</a>
<ol>
<li><a href="#localize_strings">Localize the Strings</a></li>
<li><a href="#localize_images">Localize the Images</a></li>
</ol>
</li>
<li><a href="#test_localized">Run and Test the Localized App</a></li>
</ol>
<h2>See also</h2>
<ol>
<li>{@link android.widget.Button}</li>
<li>{@link android.widget.TextView}</li>
<li>{@link android.app.AlertDialog}</li>
</ol>
</div>
</div>
<p>In this tutorial, we will create a Hello, L10N application that uses the
Android framework to selectively load resources. Then we will localize the
application by adding resources to the <code>res/</code> directory. </p>
<p>This tutorial uses the practices described in the <a
href="{@docRoot}guide/topics/resources/localization.html">Localization</a>
document. </p>
<h2 id="unlocalized">Create an Unlocalized Application</h2>
<p>The first version of the Hello, L10N application will use only the default
resource directories (<code>res/drawable</code>, <code>res/layout</code>, and
<code>res/values</code>). These resources are not localized &#8212; they are the
graphics, layout, and strings that we expect the application to use most often.
When a user runs the application in the default locale, or in a locale that the
application does not specifically support, the application will load resources
from these default directories.</p>
<p>The application consists of a simple user interface that displays two
{@link android.widget.TextView} objects and a {@link android.widget.Button} image with a
background image of a national flag. When clicked, the button displays an
{@link android.app.AlertDialog} object that shows additional text. </p>
<h3 id="create">Create the Project and Layout</h3>
<p>For this application, the default language will be British English and the
default location the United Kingdom. </p>
<ol>
<li>Start a new project and Activity called &quot;HelloL10N.&quot; If you are
using Eclipse, fill out these values in the New Android Project wizard:
<ul>
<li><em>Project name:</em> HelloL10N</li>
<li><em>Application name:</em> Hello, L10N</li>
<li><em>Package name:</em> com.example.hellol10n (or your own private
namespace)</li>
<li><em>Create Activity:</em> HelloL10N</li>
<li><em>Min SDK Version:</em> 3</li>
</ul>
<p>The basic project contains a <code>res/</code> directory with
subdirectories for the three most common types of resources: graphics
(<code>res/drawable/</code>), layouts (<code>res/layout/</code>) and strings
(<code>res/values/</code>). Most of the localization work you do later in this
tutorial will involve adding more subdirectories to the <code>res/</code>
directory.</p>
<img src="{@docRoot}images/hello_l10n/plain_project.png" alt="plain project" width="194"
height="229">
</li>
<li>Open the <code>res/layout/main.xml</code> file and replace it with the
following code:
<pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;LinearLayout xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
android:orientation=&quot;vertical&quot;
android:layout_width=&quot;fill_parent&quot;
android:layout_height=&quot;fill_parent&quot;
&gt;
&lt;TextView
android:layout_width=&quot;fill_parent&quot;
android:layout_height=&quot;wrap_content&quot;
android:gravity=&quot;center_horizontal&quot;
android:text=&quot;@string/text_a&quot;
/&gt;
&lt;TextView
android:layout_width=&quot;fill_parent&quot;
android:layout_height=&quot;wrap_content&quot;
android:gravity=&quot;center_horizontal&quot;
android:text=&quot;@string/text_b&quot;
/&gt;
&lt;Button
android:id=&quot;@+id/flag_button&quot;
android:layout_width=&quot;wrap_content&quot;
android:layout_height=&quot;wrap_content&quot;
android:layout_gravity=&quot;center&quot;
/&gt;
&lt;/LinearLayout&gt;
</pre>
<p>The LinearLayout has two {@link android.widget.TextView} objects that will
display localized text and one {@link android.widget.Button} that shows a flag.
</p>
</li>
</ol>
<h3 id="default">Create Default Resources</h3>
<p>The layout refers to resources that need to be defined. </p>
<ol>
<li>Create default text strings. To do this, open the <code>res/values/strings.xml</code> file and replace it with the following code:<br>
<pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;resources&gt;
&lt;string name=&quot;app_name&quot;&gt;Hello, L10N&lt;/string&gt;
&lt;string name=&quot;text_a&quot;&gt;Shall I compare thee to a summer&quot;'&quot;s day?&lt;/string&gt;
&lt;string name=&quot;text_b&quot;&gt;Thou art more lovely and more temperate.&lt;/string&gt;
&lt;string name=&quot;dialog_title&quot;&gt;No Localisation&lt;/string&gt;
&lt;string name=&quot;dialog_text&quot;&gt;This dialog box&quot;'&quot;s strings are not localised. For every locale, the text here will come from values/strings.xml.&lt;/string&gt;
&lt;/resources&gt;</pre>
<p>This code provides British English text for each string that the application
will use. When we localize this application, we will provide alternate text in
German, French, and Japanese for some of the strings.</p>
</li>
<li>Add a default flag graphic to the <code>res/drawable</code> folder by
saving <a href="../../../images/hello_l10n/flag.png">flag.png</a> as
<code>res/drawable/flag.png</code>. When the application is not localized, it
will show a British flag.<br>
</li>
<li>Open HelloL10N.java (in the <code>src/</code> directory) and add the
following code inside the <code>onCreate()</code> method (after
<code>setContentView</code>).
<pre>// assign flag.png to the button, loading correct flag image for current locale
Button b;
(b = (Button)findViewById(R.id.flag_button)).setBackgroundDrawable(this.getResources().getDrawable(R.drawable.flag));
// build dialog box to display when user clicks the flag
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(R.string.dialog_text)
.setCancelable(false)
.setTitle(R.string.dialog_title)
.setPositiveButton("Done", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
}
});
final AlertDialog alert = builder.create();
// set click listener on the flag to show the dialog box
b.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
alert.show();
}
});</pre>
<p class="note"><strong>Tip:</strong> In Eclipse, use
<strong>Ctrl-Shift-O</strong> (<strong>Cmd-Shift-O</strong>, on Mac) to find and
add missing import packages to your project, then save the HelloL10N.java
file.</p>
<p>The code that you added does the following:</p>
<ul>
<li>It assigns the correct flag icon to the button.
For now, no resources are defined other than the default, so this code
will always assign the contents of <code>res/drawable/flag.png</code> (the
British flag) as the flag icon, no matter what the locale. Once we add more
flags for different locales, this code will sometimes assign a different flag.
</li>
<li>It creates an {@link android.app.AlertDialog} object and sets a click listener so that when the
user clicks the button, the AlertDialog will display.
We will not localize the dialog text;
the AlertDialog will always display the <code>dialog_text</code> that is located
within <code>res/values/strings.xml</code>. </li>
</ul>
</li>
</ol>
<p>The project structure now looks like this:</p>
<img src="{@docRoot}images/hello_l10n/nonlocalized_project.png" alt="nonlocalized" width="394"
height="320">
<p class="note"><strong>Tip:</strong> If you will want to run the application on
a device and not just on an emulator, open <code>AndroidManifest.xml</code> and
add <code>android:debuggable="true"</code> inside the
<code>&lt;application&gt;</code> element. For information about setting up the
device itself so it can run applications from your system, see <a
href="{@docRoot}guide/developing/device.html">Developing on a Device</a>.</p>
<h2 id="run">Run the Unlocalized Application</h2>
<p>Save the project and run the application to see how it works. No matter what
locale your device or emulator is set to, the application runs the same way. It
should look something like this:</p>
<table border="0" cellspacing="0" cellpadding="30">
<tr>
<th scope="col">The unlocalized application, running in any locale:</th>
<th scope="col">After clicking the flag, in any locale:</th>
</tr>
<tr>
<td valign="top"><img src="{@docRoot}images/hello_l10n/nonlocalized_screenshot1.png"
alt="nonlocalized" width="321" height="366"></td>
<td><img src="{@docRoot}images/hello_l10n/nonlocalized_screenshot2.png" alt="nonlocalized2"
width="321" height="366"></td>
</tr>
</table>
<h2 id="plan">Plan the Localization</h2>
<p>The first step in localizing an application is to plan how the application
will render differently in different locales. In this application, the default
locale will be the United Kingdom. We will add some locale-specific information
for Germany, France, Canada, Japan, and the United States. Table 1 shows the
plan for how the application will appear in different locales.</p>
<p class="caption">Table 1</p>
<table border="0" cellspacing="0" cellpadding="10">
<tr>
<th scope="col" valign="bottom">Region /<br />
Language</th>
<th scope="col">United Kingdom</th>
<th scope="col">Germany</th>
<th scope="col">France</th>
<th scope="col">Canada</th>
<th scope="col">Japan</th>
<th scope="col">United States</th>
<th scope="col">Other Location</th>
</tr>
<tr>
<th scope="row"><br>
English</th>
<td> British English text; British flag <em>(default)</em></td>
<td><em>-</em></td>
<td><em>-</em></td>
<td> British English text; Canadian flag</td>
<td>-</td>
<td> British English text; U.S. flag</td>
<td> British English text; British flag <em>(default)</em></td>
</tr>
<tr>
<th scope="row">German</th>
<td>-</td>
<td>German text for <code>app_name</code>, <code>text_a</code> and
<code>text_b</code>; German flag</td>
<td>-</td>
<td>-</td>
<td>-</td>
<td>-</td>
<td>German text for <code>app_name</code>, <code>text_a</code> and
<code>text_b</code>; British flag</td>
</tr>
<tr>
<th scope="row">French</th>
<td>-</td>
<td>-</td>
<td>French text for <code>app_name</code>, <code>text_a</code> and
<code>text_b</code>; French flag</td>
<td>French text for <code>app_name</code>, <code>text_a</code> and
<code>text_b</code>; Canadian flag</td>
<td>-</td>
<td>-</td>
<td>French text for <code>app_name</code>, <code>text_a</code> and
<code>text_b</code>; British flag</td>
</tr>
<tr>
<th scope="row">Japanese</th>
<td>-</td>
<td>-</td>
<td>-</td>
<td>-</td>
<td>Japanese text for <code>text_a</code> and <code>text_b</code>; Japanese
flag</td>
<td>-</td>
<td>Japanese text for <code>text_a</code> and <code>text_b</code>; British
flag</td>
</tr>
<tr>
<th scope="row">Other Language</th>
<td>-</td>
<td>-</td>
<td>-</td>
<td>-</td>
<td>-</td>
<td>-</td>
<td> British English text; British flag <em>(default)</em></td>
</tr>
</table>
<p class="note"> Note that other behaviors are possible; for example, the
application could support Canadian English or U.S. English text. But given the
small amount of text involved, adding more versions of English would not make
this application more useful.</p>
<p>As shown in the table above, the plan calls for five flag icons in addition
to the British flag that is already in the <code>res/drawable/</code> folder. It
also calls for three sets of text strings other than the text that is in
<code>res/values/strings.xml</code>.</p>
<p>Table 2 shows where the needed text strings and flag icons will go, and
specifies which ones will be loaded for which locales. (For more about the
locale codes, <em></em>see <a
href="{@docRoot}guide/topics/resources/resources-i18n.html#AlternateResources">
Alternate Resources</a>.)</p>
<p class="caption" id="table2">Table 2</p>
<table border="1" cellspacing="0" cellpadding="5">
<tr>
<th scope="col">Locale Code</th>
<th scope="col">Language / Country</th>
<th scope="col">Location of strings.xml</th>
<th scope="col">Location of flag.png</th>
</tr>
<tr>
<td><em>Default</em></td>
<td>English / United Kingdom</td>
<td>res/values/</td>
<td>res/drawable/</td>
</tr>
<tr>
<td>de-rDE</td>
<td>German / Germany</td>
<td>res/values-de/</td>
<td>res/drawable-de-rDE/</td>
</tr>
<tr>
<td>fr-rFR</td>
<td>French / France</td>
<td>res/values-fr/</td>
<td>res/drawable-fr-rFR/</td>
</tr>
<tr>
<td>fr-rCA</td>
<td>French / Canada</td>
<td>res/values-fr/</td>
<td>res/drawable-fr-rCA/</td>
</tr>
<tr>
<td>en-rCA</td>
<td>English / Canada</td>
<td><em>(res/values/)</em></td>
<td>res/drawable-en-rCA/</td>
</tr>
<tr>
<td>ja-rJP</td>
<td>Japanese / Japan</td>
<td>res/values-ja/</td>
<td>res/drawable-ja-rJP/</td>
</tr>
<tr>
<td>en-rUS</td>
<td>English / United States</td>
<td><em>(res/values/)</em></td>
<td>res/drawable-en-rUS/</td>
</tr>
</table>
<p class="note"><strong>Tip: </strong>A folder qualifer cannot specify a region
without a language. Having a folder named <code>res/drawable-rCA/</code>,
for example, will prevent the application from compiling. </p>
<p>At run time, the application will select a set of resources to load based on the locale
that is set in the user's device. In cases where no locale-specific resources
are available, the application will fall back on the defaults. </p>
<p>For example, assume that the device's language is set to German and its
location to Switzerland. Because this application does not have a
<code>res/drawable-de-rCH/</code> directory with a <code>flag.png</code> file in it, the system
will fall back on the default, which is the UK flag located in
<code>res/drawable/flag.png</code>. The language used will be German. Showing a
British flag to German speakers in Switzerland is not ideal, but for now we will
just leave the behavior as it is. There are several ways you could improve this
application's behavior if you wanted to:</p>
<ul>
<li>Use a generic default icon. In this application, it might be something
that represents Shakespeare. </li>
<li>Create a <code>res/drawable-de/</code> folder that includes an icon that
the application will use whenever the language is set to German but the location
is not Germany. </li>
</ul>
<h2 id="localize">Localize the Application</h2>
<h3 id="localize_strings">Localize the Strings</h3>
<p>The application requires three more <code>strings.xml</code> files, one
each for German, French, and Japanese. To create these resource files within
Eclipse:</p>
<ol>
<li>Select <strong>File</strong> &gt; <strong>New</strong> &gt; <strong>Android
XML File</strong> to open the New Android XML File wizard. You can also open
the wizard by clicking its icon in the toolbar:<br />
<img src="{@docRoot}images/hello_l10n/xml_file_wizard_shortcut.png"
alt="file_wizard_shortcut" width="297"
height="90" style="margin:15px"></li>
<li>Select L10N for the Project field, and type <code>strings.xml</code> into
the File field. In the left-hand list, select Language, then click the right arrow.<br>
<img src="{@docRoot}images/hello_l10n/xml_wizard1.png" alt="res_file_copy" width="335"
height="406" style="margin:15px"></li>
<li>Type <code>de</code> in the Language box and click Finish.<br>
<img src="{@docRoot}images/hello_l10n/xml_wizard2.png" alt="res_file_copy" width="306"
height="179">
<p>A new file, <code>res/values-de/strings.xml</code>, now appears among the project
files.</p></li>
<li>Repeat the steps twice more, for the language codes <code>fr</code> and
<code>ja</code>.
Now the project includes these new skeleton files: <br />
<code>res/<strong>values-de</strong>/strings.xml</code><br />
<code>res/<strong>values-fr</strong>/strings.xml</code><br />
<code>res/<strong>values-ja</strong>/strings.xml</code><br />
</li>
<li>Add localized text to the new files. To do
this, open the <code>res/values-<em>&lt;qualifier&gt;</em>/strings.xml</code> files and
replace the code as follows:</li>
</ol>
<table border="0" cellspacing="0" cellpadding="0">
<tr>
<th scope="col">File</th>
<th scope="col">Replace the contents with the following code:</th>
</tr>
<tr>
<td><code>res/values-de/strings.xml</code></td>
<td><pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;resources&gt;
&lt;string name=&quot;app_name&quot;&gt;Hallo, Lokalisierung&lt;/string&gt;
&lt;string name=&quot;text_a&quot;&gt;Soll ich dich einem Sommertag vergleichen,&lt;/string&gt;
&lt;string name=&quot;text_b&quot;&gt;Der du viel lieblicher und sanfter bist?&lt;/string&gt;
&lt;/resources&gt;</pre></td>
</tr>
<tr>
<td><code>res/values-fr/strings.xml</code></td>
<td><pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;resources&gt;
&lt;string name=&quot;app_name&quot;&gt;Bonjour, Localisation&lt;/string&gt;
&lt;string name=&quot;text_a&quot;&gt;Irai-je te comparer au jour d'été?&lt;/string&gt;
&lt;string name=&quot;text_b&quot;&gt;Tu es plus tendre et bien plus tempéré.&lt;/string&gt;
&lt;/resources&gt; </pre></td>
</tr>
<tr>
<td><code>res/values-ja/strings.xml</code></td>
<td>
<pre>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;resources&gt;
&lt;string name=&quot;text_a&quot;&gt;あなたをなにかにたとえるとしたら夏の一日でしょうか？&lt;/string&gt;
&lt;string name=&quot;text_b&quot;&gt;だがあなたはもっと美しく、もっとおだやかです。&lt;/string&gt;
&lt;/resources&gt;</pre></td>
</tr>
</table>
<p class="note"><b>Tip:</b> In the
<code>values-<em>&lt;qualifier&gt;</em>/strings.xml</code> files, you only need to
include text for strings that are different from the default strings. For
example, when the application runs on a device that is configured for Japanese,
the plan is for <code>text_a</code> and <code>text_b</code> to be in Japanese
while all the other text is in English, so
<code>res/values-ja/strings.xml</code> only needs to include <code>text_a</code>
and <code>text_b</code>.</p>
<h3 id="localize_images">Localize the Images</h3>
<p>As shown in <a href="#table2">Table 2</a>, the application needs six more
drawable folders, each containing a <code>flag.png</code> icon. Add the needed
icons and folders to your project:</p>
<ol>
<li>Save this <a href="../../../images/hello_l10n/drawable-de-rDE/flag.png">German flag icon</a>
as <code>res/drawable-de-rDE/flag.png</code> in the application's project
workspace.
<p>For example:</p>
<ol>
<li>Click the link to open the flag image.</li>
<li>Save the image in
<code><em>your-workspace</em>/HelloL10N/res/drawable-de-rDE/</code> .</li>
</ol>
</li>
<li>Save this <a href="../../../images/hello_l10n/drawable-fr-rFR/flag.png">French flag icon</a>
as <code>res/drawable-fr-rFR/flag.png</code> in the application's project
workspace. </li>
<li>Save this <a href="../../../images/hello_l10n/drawable-fr-rCA/flag.png">Canadian flag icon</a>
as <code>res/drawable-fr-rCA/flag.png</code> in the project workspace. </li>
<li>Save the <a href="../../../images/hello_l10n/drawable-en-rCA/flag.png">Canadian flag icon</a>
again, this time as <code>res/drawable-en-rCA/flag.png</code> in the project
workspace. (Why not have just <em>one</em> folder that contains the Canadian
flag? Because a folder qualifer cannot specify a region without a language.
You cannot have a folder named <code>drawable-rCA/</code>; instead you must
create two separate folders, one for each of the Canadian languages represented
in the application.)</li>
<li>Save this <a href="../../../images/hello_l10n/drawable-ja-rJP/flag.png">Japanese flag icon</a>
as <code>res/drawable-ja-rJP/flag.png</code> in the project workspace. </li>
<li>Save this <a href="../../../images/hello_l10n/drawable-en-rUS/flag.png">United States flag
icon</a> as <code>res/drawable-en-rUS/flag.png</code> in the project workspace.
</li>
</ol>
<p>If you are using Eclipse, refresh the project (F5). The new
<code>res/drawable-<em>&lt;qualifier&gt;</em>/</code> folders should appear in the
project view. </p>
<h2 id="test_localized">Run and Test the Localized Application</h2>
<p>Once you've added the localized string and image resources, you are ready to
run the application and test its handling of them. To change the locale
on a device or in the emulator, use the Settings
application (Home &gt; Menu &gt; Settings &gt; Locale &amp; text &gt; Select
locale). Depending on how a device was configured, it might not offer any
alternate locales via the Settings application, or might offer only a few. The
emulator, on the other hand, will offer a selection of all the locales that are
available in the Android system image. </p>
<p>To set the emulator to a locale that is not available in the system image,
use the Custom Locale application, which is available in the Application
tab:</p>
<p><img src="{@docRoot}images/hello_l10n/custom_locale_app.png" alt="custom locale app" width="163"
height="158" style="margin-left:15px"></p>
<p>To switch to a new locale, long-press a locale name:</p>
<p><img src="{@docRoot}images/hello_l10n/using_custom_locale.png" alt="using custom locale"
width="512" height="299" style="margin-left:15px"></p>
<p>For a list of locales available on different versions of the Android platform,
refer to the platform notes documents, listed under "Downloadable SDK Components"
in the "SDK" tab. For example, <a
href="{@docRoot}sdk/android-2.0.html#locs">Android 2.0 locales</a>.</p>
<p>Run the application for each of the expected locales, plus one unexpected
locale. Here are some of the results you should see:</p>
<table border="0" cellspacing="0" cellpadding="05">
<tr>
<th scope="col">Locale</th>
<th scope="col">Opening screen of application</th>
</tr>
<tr>
<td>German / Germany
<br />Specifically supported by the Hello, L10N application.</td>
<td><img src="{@docRoot}images/hello_l10n/german_screenshot.png" alt="custom locale app"
width="321" height="175" align="right"
style="margin-left:10px;margin-right:20px"></td>
</tr>
<tr>
<td>French / Canada
<br />Specifically supported by the Hello, L10N application.</td>
<td><img src="{@docRoot}images/hello_l10n/frenchCA_screenshot.png" alt="custom locale app"
width="321" height="175" align="right"
style="margin-left:10px;margin-right:20px"></td>
</tr>
<tr>
<td>German / Switzerland
<br />Only the language is specifically supported by
the Hello, L10N application.</td>
<td><img src="{@docRoot}images/hello_l10n/germanCH_screenshot.png" alt="custom locale app"
width="321" height="175" align="right"
style="margin-left:10px;margin-right:20px">`</td>
</tr>
<tr>
<td>Japanese
<br />Specifically supported by the Hello, L10N application.
</td>
<td><img src="{@docRoot}images/hello_l10n/japanese_screenshot.png" alt="custom locale app"
width="321" height="220" align="right"
style="margin-left:10px;margin-right:20px">`</td>
</tr>
<tr>
<td>Romansh / Switzerland (custom locale <code>rm_CH</code>)
<br />Not specifically supported by the Hello, L10N
application, so the application uses the default resources.</td>
<td><img src="{@docRoot}images/hello_l10n/romanshCH_screenshot.png" alt="custom locale app"
width="321" height="175" align="right"
style="margin-left:10px;margin-right:20px"></td>
</tr>
</table>

BIN
base/docs/html/guide/tutorials/notepad/codelab/NotepadCodeLab.zip Normal file
View File

Binary file not shown.

142
base/docs/html/guide/tutorials/notepad/index.jd Normal file
View File

@ -0,0 +1,142 @@
page.title=Notepad Tutorial
@jd:body
<p>This tutorial on writing a notepad application gives you a &quot;hands-on&quot; introduction
to the Android framework and the tools you use to build applications on it.
Starting from a preconfigured project file, it guides you through the process of
developing a simple notepad application and provides concrete examples of how to
set up the project, develop the application logic and user interface, and then
compile and run the application. </p>
<p>The tutorial presents the application development as a set of
exercises (see below), each consisting of several steps. You should follow
the steps in each exercise to gradually build and refine your
application. The exercises explain each step in detail and provide all the
sample code you need to complete the application. </p>
<p>When you are finished with the tutorial, you will have created a functioning
Android application and will have learned many of the most important
concepts in Android development. If you want to add more complex features to
your application, you can examine the code in an alternative implementation
of a Note Pad application, in the
<a href="{@docRoot}resources/samples/index.html">Sample Code</a> section. </p>
<a name="who"></a>
<h2>Who Should Use this Tutorial</h2>
<p>This tutorial is designed for experienced developers, especially those with
knowledge of the Java programming language. If you haven't written Java
applications before, you can still use the tutorial, but you might need to work
at a slower pace. </p>
<p>Also note that this tutorial uses
the Eclipse development environment, with the Android plugin installed. If you
are not using Eclipse, you can follow the exercises and build the application,
but you will need to determine how to accomplish the Eclipse-specific
steps in your environment. </p>
<a name="preparing"></a>
<h2>Preparing for the Exercises</h2>
<p>The tutorial assumes that you have some familiarity with basic Android
application concepts and terminology. If you are not, you
should read <a href="{@docRoot}guide/topics/fundamentals.html">Application
Fundamentals</a> before continuing. </p>
<p>This tutorial also builds on the introductory information provided in the
<a href="{@docRoot}resources/tutorials/hello-world.html">Hello World</a>
tutorial, which explains how to set up your Eclipse environment
for building Android applications. We recommend you complete the Hello World
tutorial before starting this one.</p>
<p>To prepare for this lesson:</p>
<ol>
<li>Download the <a href="codelab/NotepadCodeLab.zip">project
exercises archive (.zip)</a>.</li>
<li>Unpack the archive file to a suitable location on your machine.</li>
<li>Open the <code>NotepadCodeLab</code> folder.</li>
</ol>
<p>Inside the <code>NotepadCodeLab</code> folder, you should see six project
files: <code>Notepadv1</code>,
<code>Notepadv2</code>, <code>Notepadv3</code>,
<code>Notepadv1Solution</code>, <code>Notepadv2Solution</code>
and <code>Notepadv3Solution</code>. The <code>Notepadv#</code> projects are
the starting points for each of the exercises, while the
<code>Notepadv#Solution</code> projects are the exercise
solutions. If you are having trouble with a particular exercise, you
can compare your current work against the exercise solution.</p>
<a name="exercises"></a>
<h2> Exercises</h2>
<p>The table below lists the tutorial exercises and describes the development
areas that each covers. Each exercise assumes that you have completed any
previous exercises.</p>
<table border="0" style="padding:4px;spacing:2px;" summary="This
table lists the
tutorial examples and describes what each covers. ">
<tr>
<th width="120"><a href="{@docRoot}resources/tutorials/notepad/notepad-ex1.html">Exercise
1</a></th>
<td>Start here. Construct a simple notes list that lets the user add new notes but not
edit them. Demonstrates the basics of <code>ListActivity</code> and creating
and handling
menu options. Uses a SQLite database to store the notes.</td>
</tr>
<tr>
<th><a href="{@docRoot}resources/tutorials/notepad/notepad-ex2.html">Exercise 2</a></th>
<td>Add a second Activity to the
application. Demonstrates constructing a
new Activity, adding it to the Android manifest, passing data between the
activities, and using more advanced screen layout. Also shows how to
invoke another Activity to return a result, using
<code>startActivityForResult()</code>.</td>
</tr>
<tr>
<th><a href="{@docRoot}resources/tutorials/notepad/notepad-ex3.html">Exercise 3</a></th>
<td>Add handling of life-cycle events to
the application, to let it
maintain application state across the life cycle. </td>
</tr>
<tr>
<th><a href="{@docRoot}resources/tutorials/notepad/notepad-extra-credit.html">Extra
Credit</a></th>
<td>Demonstrates how to use the Eclipse
debugger and how you can use it to
view life-cycle events as they are generated. This section is optional but
highly recommended.</td>
</tr>
</table>
<a name="other"></a>
<h2>Other Resources and Further Learning</h2>
<ul>
<li>For a lighter but broader introduction to concepts not covered in the
tutorial,
take a look at <a href="{@docRoot}resources/faq/commontasks.html">Common Android Tasks</a>.</li>
<li>The Android SDK includes a variety of fully functioning sample applications
that make excellent opportunities for further learning. You can find the sample
applications in the <code>samples/</code> directory of your downloaded SDK, or browser them
here, in the <a href="{@docRoot}resources/samples/index.html">Sample Code</a> section.</li>
<li>This tutorial draws from the full Notepad application included in the
<code>samples/</code> directory of the SDK, though it does not match it exactly.
When you are done with the tutorial,
it is highly recommended that you take a closer look at this version of the Notepad
application,
as it demonstrates a variety of interesting additions for your application,
such as:</li>
<ul>
<li>Setting up a custom striped list for the list of notes.</li>
<li>Creating a custom text edit view that overrides the <code>draw()</code>
method to make it look like a lined notepad.</li>
<li>Implementing a full <code>ContentProvider</code> for notes.</li>
<li>Reverting and discarding edits instead of just automatically saving
them.</li>
</ul>
</ul>

582
base/docs/html/guide/tutorials/notepad/notepad-ex1.jd Normal file
View File

@ -0,0 +1,582 @@
page.title=Notepad Exercise 1
parent.title=Notepad Tutorial
parent.link=index.html
@jd:body
<p><em>In this exercise, you will construct a simple notes list that lets the
user add new notes but not edit them. The exercise demonstrates:</em></p>
<ul>
<li><em>The basics of <code>ListActivities</code> and creating and handling menu
options. </em></li>
<li><em>How to use a SQLite database to store the notes.</em></li>
<li><em>How to bind data from a database cursor into a ListView using a
SimpleCursorAdapter.</em></li>
<li><em>The basics of screen layouts, including how to lay out a list view, how
you can add items to the activity menu, and how the activity handles those menu
selections. </em></li>
</ul>
<div style="float:right;white-space:nowrap">
<span style="color:#BBB;">
[<a href="notepad-ex1.html" style="color:#BBB;">Exercise 1</a>]</span>
[<a href="notepad-ex2.html">Exercise 2</a>]
[<a href="notepad-ex3.html">Exercise 3</a>]
[<a href="notepad-extra-credit.html">Extra Credit</a>]
</div>
<h2>Step 1</h2>
<p>Open up the <code>Notepadv1</code> project in Eclipse.</p>
<p><code>Notepadv1</code> is a project that is provided as a starting point. It
takes care of some of the boilerplate work that you have already seen if you
followed the <a href="{@docRoot}resources/tutorials/hello-world.html">Hello,
World</a> tutorial.</p>
<ol>
<li>
Start a new Android Project by clicking <strong>File</strong> >
<strong>New</strong> > <strong>Android Project</strong>.</li>
<li>
In the New Android Project dialog, select <strong>Create project from existing source</strong>.</li>
<li>
Click <strong>Browse</strong> and navigate to where you copied the <code>NotepadCodeLab</code>
(downloaded during <a href="{@docRoot}resources/tutorials/notepad/index.html#preparing">setup</a>)
and select <code>Notepadv1</code>.</li>
<li>
The Project Name and other properties should be automatically filled for you.
You must select the Build Target&mdash;we recommend selecting a target with the
lowest platform version available. Also add an integer to the Min SDK Version field
that matches the API Level of the selected Build Target.</li>
<li>
Click <strong>Finish</strong>. The <code>Notepadv1</code> project should open and be
visible in your Eclipse package explorer.</li>
</ol>
<p>If you see an error about <code>AndroidManifest.xml</code>, or some
problems related to an Android zip file, right click on the project and
select <strong>Android Tools</strong> > <strong>Fix Project Properties</strong>.
(The project is looking in the wrong location for the library file,
this will fix it for you.)</p>
<h2>Step 2</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Accessing and modifying data</h2>
<p>For this
exercise, we are using a SQLite database to store our data. This is useful
if only <em>your</em> application will need to access or modify the data. If you wish for
other activities to access or modify the data, you have to expose the data using a
{@link android.content.ContentProvider ContentProvider}.</p>
<p>If you are interested, you can find out more about
<a href="{@docRoot}guide/topics/providers/content-providers.html">content providers</a> or the
whole
subject of <a href="{@docRoot}guide/topics/data/data-storage.html">Data Storage</a>.
The NotePad sample in the <code>samples/</code> folder of the SDK also has an example of how
to create a ContentProvider.</p>
</div>
</div>
<p>Take a look at the <code>NotesDbAdapter</code> class &mdash; this class is provided to
encapsulate data access to a SQLite database that will hold our notes data
and allow us to update it.</p>
<p>At the top of the class are some constant definitions that will be used in the application
to look up data from the proper field names in the database. There is also a database creation
string defined, which is used to create a new database schema if one doesn't exist already.</p>
<p>Our database will have the name <code>data</code>, and have a single table called
<code>notes</code>, which in turn has three fields: <code>_id</code>, <code>title</code> and
<code>body</code>. The <code>_id</code> is named with an underscore convention used in a number of
places inside the Android SDK and helps keep a track of state. The <code>_id</code>
usually has to be specified when querying or updating the database (in the column projections
and so on). The other two fields are simple text fields that will store data.
</p>
<p>The constructor for <code>NotesDbAdapter</code> takes a Context, which allows it to communicate with aspects
of the Android operating system. This is quite common for classes that need to touch the
Android system in some way. The Activity class implements the Context class, so usually you will just pass
<code>this</code> from your Activity, when needing a Context.</p>
<p>The <code>open()</code> method calls up an instance of DatabaseHelper, which is our local
implementation of the SQLiteOpenHelper class. It calls <code>getWritableDatabase()</code>,
which handles creating/opening a database for us.</p>
<p><code>close()</code> just closes the database, releasing resources related to the
connection.</p>
<p><code>createNote()</code> takes strings for the title and body of a new note,
then creates that note in the database. Assuming the new note is created successfully, the
method also returns the row <code>_id</code> value for the newly created note.</p>
<p><code>deleteNote()</code> takes a <var>rowId</var> for a particular note, and deletes that note from
the database.</p>
<p><code>fetchAllNotes()</code> issues a query to return a {@link android.database.Cursor} over all notes in the
database. The <code>query()</code> call is worth examination and understanding. The first field is the
name of the database table to query (in this case <code>DATABASE_TABLE</code> is "notes").
The next is the list of columns we want returned, in this case we want the <code>_id</code>,
<code>title</code> and <code>body</code> columns so these are specified in the String array.
The remaining fields are, in order: <code>selection</code>,
<code>selectionArgs</code>, <code>groupBy</code>, <code>having</code> and <code>orderBy</code>.
Having these all <code>null</code> means we want all data, need no grouping, and will take the default
order. See {@link android.database.sqlite.SQLiteDatabase SQLiteDatabase} for more details.</p>
<p class="note"><b>Note:</b> A Cursor is returned rather than a collection of rows. This allows
Android to use resources efficiently -- instead of putting lots of data straight into memory
the cursor will retrieve and release data as it is needed, which is much more efficient for
tables with lots of rows.</p>
<p><code>fetchNote()</code> is similar to <code>fetchAllNotes()</code> but just gets one note
with the <var>rowId</var> we specify. It uses a slightly different version of the
{@link android.database.sqlite.SQLiteDatabase} <code>query()</code> method.
The first parameter (set <em>true</em>) indicates that we are interested
in one distinct result. The <var>selection</var> parameter (the fourth parameter) has been specified to search
only for the row "where _id =" the <var>rowId</var> we passed in. So we are returned a Cursor on
the one row.</p>
<p>And finally, <code>updateNote()</code> takes a <var>rowId</var>, <var>title</var> and <var>body</var>, and uses a
{@link android.content.ContentValues ContentValues} instance to update the note of the given
<var>rowId</var>.</p>
<h2 style="clear:right;">Step 3</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Layouts and activities</h2>
<p>Most Activity classes will have a layout associated with them. The layout
will be the "face" of the Activity to the user. In this case our layout will
take over the whole screen and provide a list of notes.</p>
<p>Full screen layouts are not the only option for an Activity however. You
might also want to use a <a
href="{@docRoot}resources/faq/commontasks.html#floatingorfull">floating
layout</a> (for example, a <a
href="{@docRoot}resources/faq/commontasks.html#dialogsandalerts">dialog
or alert</a>),
or perhaps you don't need a layout at all (the Activity will be invisible
to the user unless you specify some kind of layout for it to use).</p>
</div>
</div>
<p>Open the <code>notepad_list.xml</code> file in <code>res/layout</code>
and
take a look at it. (You may have to
hit the <em>xml</em> tab, at the bottom, in order to view the XML markup.)</p>
<p>This is a mostly-empty layout definition file. Here are some
things you should know about a layout file:</p>
<ul>
<li>
All Android layout files must start with the XML header line:
<code>&lt;?xml version="1.0" encoding="utf-8"?&gt;</code>. </li>
<li>
The next definition will often (but not always) be a layout
definition of some kind, in this case a <code>LinearLayout</code>. </li>
<li>
The XML namespace of Android should always be defined in
the top level component or layout in the XML so that <code>android:</code> tags can
be used through the rest of the file:
<p><code>xmlns:android="http://schemas.android.com/apk/res/android"</code></p>
</li>
</ul>
<h2 style="clear:right;">Step 4</h2>
<p>We need to create the layout to hold our list. Add code inside
of the <code>LinearLayout</code> element so the whole file looks like this: </p>
<pre>
&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;LinearLayout xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
android:layout_width=&quot;wrap_content&quot;
android:layout_height=&quot;wrap_content&quot;&gt;
&lt;ListView android:id=&quot;@android:id/list&quot;
android:layout_width=&quot;wrap_content&quot;
android:layout_height=&quot;wrap_content&quot;/&gt;
&lt;TextView android:id=&quot;@android:id/empty&quot;
android:layout_width=&quot;wrap_content&quot;
android:layout_height=&quot;wrap_content&quot;
android:text=&quot;@string/no_notes&quot;/&gt;
&lt;/LinearLayout&gt;
</pre>
<ul>
<li>
The <strong>&#64;</strong> symbol in the id strings of the <code>ListView</code> and
<code>TextView</code> tags means
that the XML parser should parse and expand the rest of
the id string and use an ID resource.</li>
<li>
The <code>ListView</code> and <code>TextView</code> can be
thought as two alternative views, only one of which will be displayed at once.
ListView will be used when there are notes to be shown, while the TextView
(which has a default value of "No Notes Yet!" defined as a string
resource in <code>res/values/strings.xml</code>) will be displayed if there
aren't any notes to display.</li>
<li>The <code>list</code> and <code>empty</code> IDs are
provided for us by the Android platform, so, we must
prefix the <code>id</code> with <code>android:</code> (e.g., <code>@android:id/list</code>).</li>
<li>The View with the <code>empty</code> id is used
automatically when the {@link android.widget.ListAdapter} has no data for the ListView. The
ListAdapter knows to look for this name by default. Alternatively, you could change the
default empty view by using {@link android.widget.AdapterView#setEmptyView(View)}
on the ListView.
<p>
More broadly, the <code>android.R</code> class is a set of predefined
resources provided for you by the platform, while your project's
<code>R</code> class is the set of resources your project has defined.
Resources found in the <code>android.R</code> resource class can be
used in the XML files by using the <code>android:</code> name space prefix
(as we see here).</p>
</li>
</ul>
<h2 style="clear:right;">Step 5</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Resources and the R class</h2>
<p>The folders under res/ in the Eclipse project are for resources.
There is a <a href="{@docRoot}resources/faq/commontasks.html#filelist">specific structure</a>
to the
folders and files under res/.</p>
<p>Resources defined in these folders and files will have
corresponding entries in the R class allowing them to be easily accessed
and used from your application. The R class is automatically generated using the contents
of the res/ folder by the eclipse plugin (or by aapt if you use the command line tools).
Furthermore, they will be bundled and deployed for you as part of the application.</p>
</p>
</div>
</div>
<p>To make the list of notes in the ListView, we also need to define a View for each row:</p>
<ol>
<li>
Create a new file under <code>res/layout</code> called
<code>notes_row.xml</code>. </li>
<li>
Add the following contents (note: again the XML header is used, and the
first node defines the Android XML namespace)<br>
<pre style="overflow:auto">
&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;TextView android:id=&quot;&#64;+id/text1&quot;
xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
android:layout_width=&quot;wrap_content&quot;
android:layout_height=&quot;wrap_content&quot;/&gt;</pre>
<p>
This is the View that will be used for each notes title row &mdash; it has only
one text field in it. </p>
<p>In this case we create a new id called <code>text1</code>. The
<strong>+</strong> after the <strong>@</strong> in the id string indicates that the id should
be automatically created as a resource if it does not already exist, so we are defining
<code>text1</code> on the fly and then using it.</p>
</li>
<li>Save the file.</li>
</ol>
<p>Open the <code>R.java</code> class in the
project and look at it, you should see new definitions for
<code>notes_row</code> and <code>text1</code> (our new definitions)
meaning we can now gain access to these from the our code. </p>
<h2 style="clear:right;">Step 6</h2>
<p>Next, open the <code>Notepadv1</code> class in the source. In the following steps, we are going to
alter this class to become a list adapter and display our notes, and also
allow us to add new notes.</p>
<p><code>Notepadv1</code> will inherit from a subclass
of <code>Activity</code> called a <code>ListActivity</code>,
which has extra functionality to accommodate the kinds of
things you might want to do with a list, for
example: displaying an arbitrary number of list items in rows on the screen,
moving through the list items, and allowing them to be selected.</p>
<p>Take a look through the existing code in <code>Notepadv1</code> class.
There is a currently an unused private field called <code>mNoteNumber</code> that
we will use to create numbered note titles.</p>
<p>There are also three override methods defined:
<code>onCreate</code>, <code>onCreateOptionsMenu</code> and
<code>onOptionsItemSelected</code>; we need to fill these
out:</p>
<ul>
<li><code>onCreate()</code> is called when the activity is
started &mdash; it is a little like the "main" method for an Activity. We use
this to set up resources and state for the activity when it is
running.</li>
<li><code>onCreateOptionsMenu()</code> is used to populate the
menu for the Activity. This is shown when the user hits the menu button,
and
has a list of options they can select (like "Create
Note"). </li>
<li><code>onOptionsItemSelected()</code> is the other half of the
menu equation, it is used to handle events generated from the menu (e.g.,
when the user selects the "Create Note" item).
</li>
</ul>
<h2>Step 7</h2>
<p>Change the inheritance of <code>Notepadv1</code> from
<code>Activity</code>
to <code>ListActivity</code>:</p>
<pre>public class Notepadv1 extends ListActivity</pre>
<p>Note: you will have to import <code>ListActivity</code> into the
Notepadv1
class using Eclipse, <strong>ctrl-shift-O</strong> on Windows or Linux, or
<strong>cmd-shift-O</strong> on the Mac (organize imports) will do this for you
after you've written the above change.</p>
<h2>Step 8</h2>
<p>Fill out the body of the <code>onCreate()</code> method.</p>
<p>Here we will set the title for the Activity (shown at the top of the
screen), use the <code>notepad_list</code> layout we created in XML,
set up the <code>NotesDbAdapter</code> instance that will
access notes data, and populate the list with the available note
titles:</p>
<ol>
<li>
In the <code>onCreate</code> method, call <code>super.onCreate()</code> with the
<code>savedInstanceState</code> parameter that's passed in.</li>
<li>
Call <code>setContentView()</code> and pass <code>R.layout.notepad_list</code>.</li>
<li>
At the top of the class, create a new private class field called <code>mDbHelper</code> of class
<code>NotesDbAdapter</code>.
</li>
<li>
Back in the <code>onCreate</code> method, construct a new
<code>NotesDbAdapter</code>
instance and assign it to the <code>mDbHelper</code> field (pass
<code>this</code> into the constructor for <code>DBHelper</code>)
</li>
<li>
Call the <code>open()</code> method on <code>mDbHelper</code> to open (or create) the
database.
</li>
<li>
Finally, call a new method <code>fillData()</code>, which will get the data and
populate the ListView using the helper &mdash; we haven't defined this method yet. </li>
</ol>
<p>
<code>onCreate()</code> should now look like this:</p>
<pre>
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.notepad_list);
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
fillData();
}</pre>
<p>And be sure you have the <code>mDbHelper</code> field definition (right
under the mNoteNumber definition): </p>
<pre> private NotesDbAdapter mDbHelper;</pre>
<h2>Step 9</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>More about menus</h2>
<p>The notepad application we are constructing only scratches the
surface with <a href="{@docRoot}resources/faq/commontasks.html#addmenuitems">menus</a>. </p>
<p>You can also <a href="{@docRoot}resources/faq/commontasks.html#menukeyshortcuts">add
shortcut keys for menu items</a>, <a
href="{@docRoot}resources/faq/commontasks.html#menukeyshortcuts">create
submenus</a> and even <a href="{@docRoot}resources/faq/commontasks.html#addingtoothermenus">add
menu items to other applications!</a>. </p>
</div>
</div>
<p>Fill out the body of the <code>onCreateOptionsMenu()</code> method.</p>
<p>We will now create the "Add Item" button that can be accessed by pressing the menu
button on the device. We'll specify that it occupy the first position in the menu.</p>
<ol>
<li>
In <code>strings.xml</code> resource (under <code>res/values</code>), add
a new string named "menu_insert" with its value set to <code>Add Item</code>:
<pre>&lt;string name="menu_insert"&gt;Add Item&lt;/string&gt;</pre>
<p>Then save the file and return to <code>Notepadv1</code>.</p>
</li>
<li>Create a menu position constant at the top of the class:
<pre>public static final int INSERT_ID = Menu.FIRST;</pre>
</li>
<li>In the <code>onCreateOptionsMenu()</code> method, change the
<code>super</code> call so we capture the boolean return as <code>result</code>. We'll return this value at the end.</li>
<li>Then add the menu item with <code>menu.add()</code>.</li>
</ol>
<p>The whole method should now look like this:
<pre>
&#64;Override
public boolean onCreateOptionsMenu(Menu menu) {
boolean result = super.onCreateOptionsMenu(menu);
menu.add(0, INSERT_ID, 0, R.string.menu_insert);
return result;
}</pre>
<p>The arguments passed to <code>add()</code> indicate: a group identifier for this menu (none,
in this case), a unique ID (defined above), the order of the item (zero indicates no preference),
and the resource of the string to use for the item.</p>
<h2 style="clear:right;">Step 10</h2>
<p>Fill out the body of the <code>onOptionsItemSelected()</code> method:</p>
<p>This is going
to handle our new "Add Note" menu item. When this is selected, the
<code>onOptionsItemSelected()</code> method will be called with the
<code>item.getId()</code> set to <code>INSERT_ID</code> (the constant we
used to identify the menu item). We can detect this, and take the
appropriate actions:</p>
<ol>
<li>
The <code>super.onOptionsItemSelected(item)</code> method call goes at the
end of this method &mdash; we want to catch our events first! </li>
<li>
Write a switch statement on <code>item.getItemId()</code>.
<p>In the case of <var>INSERT_ID</var>, call a new method, <code>createNote()</code>,
and return true, because we have handled this event and do not want to
propagate it through the system.</p>
</li>
<li>Return the result of the superclass' <code>onOptionsItemSelected()</code>
method at the end.</li>
</ol>
<p>
The whole <code>onOptionsItemSelect()</code> method should now look like
this:</p>
<pre>
&#64;Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case INSERT_ID:
createNote();
return true;
}
return super.onOptionsItemSelected(item);
}</pre>
<h2>Step 11</h2>
<p>Add a new <code>createNote()</code> method:</p>
<p>In this first version of
our application, <code>createNote()</code> is not going to be very useful.
We will simply
create a new note with a title assigned to it based on a counter ("Note 1",
"Note 2"...) and with an empty body. At present we have no way of editing
the contents of a note, so for now we will have to be content making one
with some default values:</p>
<ol>
<li>Construct the name using "Note" and the counter we defined in the class: <code>
String noteName = "Note " + mNoteNumber++</code></li>
<li>
Call <code>mDbHelper.createNote()</code> using <code>noteName</code> as the
title and <code>""</code> for the body
</li>
<li>
Call <code>fillData()</code> to populate the list of notes (inefficient but
simple) &mdash; we'll create this method next.</li>
</ol>
<p>
The whole <code>createNote()</code> method should look like this: </p>
<pre>
private void createNote() {
String noteName = &quot;Note &quot; + mNoteNumber++;
mDbHelper.createNote(noteName, &quot;&quot;);
fillData();
}</pre>
<h2>Step 12</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>List adapters</h2>
<p>Our example uses a {@link android.widget.SimpleCursorAdapter
SimpleCursorAdapter} to bind a database {@link android.database.Cursor Cursor}
into a ListView, and this is a common way to use a {@link android.widget.ListAdapter
ListAdapter}. Other options exist like {@link android.widget.ArrayAdapter ArrayAdapter} which
can be used to take a List or Array of in-memory data and bind it in to
a list as well.</p>
</div>
</div>
<p>Define the <code>fillData()</code> method:</p>
<p>This
method uses <code>SimpleCursorAdapter,</code> which takes a database <code>Cursor</code>
and binds it to fields provided in the layout. These fields define the row elements of our list
(in this case we use the <code>text1</code> field in our
<code>notes_row.xml</code> layout), so this allows us to easily populate the list with
entries from our database.</p>
<p>To do this we have to provide a mapping from the <code>title</code> field in the returned Cursor, to
our <code>text1</code> TextView, which is done by defining two arrays: the first a string array
with the list of columns to map <em>from</em> (just "title" in this case, from the constant
<code>NotesDbAdapter.KEY_TITLE</code>) and, the second, an int array
containing references to the views that we'll bind the data <em>into</em>
(the <code>R.id.text1</code> TextView).</p>
<p>This is a bigger chunk of code, so let's first take a look at it:</p>
<pre>
private void fillData() {
// Get all of the notes from the database and create the item list
Cursor c = mDbHelper.fetchAllNotes();
startManagingCursor(c);
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
// Now create an array adapter and set it to display using our row
SimpleCursorAdapter notes =
new SimpleCursorAdapter(this, R.layout.notes_row, c, from, to);
setListAdapter(notes);
}</pre>
<p>Here's what we've done:</p>
<ol>
<li>
After obtaining the Cursor from <code>mDbHelper.fetchAllNotes()</code>, we
use an Activity method called
<code>startManagingCursor()</code> that allows Android to take care of the
Cursor lifecycle instead of us needing to worry about it. (We will cover the implications
of the lifecycle in exercise 3, but for now just know that this allows Android to do some
of our resource management work for us.)</li>
<li>
Then we create a string array in which we declare the column(s) we want
(just the title, in this case), and an int array that defines the View(s)
to which we'd like to bind the columns (these should be in order, respective to
the string array, but here we only have one for each).</li>
<li>
Next is the SimpleCursorAdapter instantiation.
Like many classes in Android, the SimpleCursorAdapter needs a Context in order to do its
work, so we pass in <code>this</code> for the context (since subclasses of Activity
implement Context). We pass the <code>notes_row</code> View we created as the receptacle
for the data, the Cursor we just created, and then our arrays.</li>
</ol>
<p>
In the future, remember that the mapping between the <strong>from</strong> columns and <strong>to</strong> resources
is done using the respective ordering of the two arrays. If we had more columns we wanted
to bind, and more Views to bind them in to, we would specify them in order, for example we
might use <code>{ NotesDbAdapter.KEY_TITLE, NotesDbAdapter.KEY_BODY }</code> and
<code>{ R.id.text1, R.id.text2 }</code> to bind two fields into the row (and we would also need
to define text2 in the notes_row.xml, for the body text). This is how you can bind multiple fields
into a single row (and get a custom row layout as well).</p>
<p>
If you get compiler errors about classes not being found, ctrl-shift-O or
(cmd-shift-O on the mac) to organize imports.
</p>
<h2 style="clear:right;">Step 13</h2>
<p>Run it!
<ol>
<li>
Right click on the <code>Notepadv1</code> project.</li>
<li>
From the popup menu, select <strong>Run As</strong> &gt;
<strong>Android Application</strong>.</li>
<li>
If you see a dialog come up, select Android Launcher as the way of running
the application (you can also use the link near the top of the dialog to
set this as your default for the workspace; this is recommended as it will
stop the plugin from asking you this every time).</li>
<li>Add new notes by hitting the menu button and selecting <em>Add
Item</em> from the menu.</li>
</ol>
<h2 style="clear:right;">Solution and Next Steps</h2>
<p>You can see the solution to this class in <code>Notepadv1Solution</code>
from
the zip file to compare with your own.</p>
<p>Once you are ready, move on to <a href="notepad-ex2.html">Tutorial
Exercise 2</a> to add the ability to create, edit and delete notes.</p>

641
base/docs/html/guide/tutorials/notepad/notepad-ex2.jd Normal file
View File

@ -0,0 +1,641 @@
Rpage.title=Notepad Exercise 2
parent.title=Notepad Tutorial
parent.link=index.html
@jd:body
<p><em>In this exercise, you will add a second Activity to your notepad application, to let the user
create and edit notes. You will also allow the user to delete existing notes through a context menu.
The new Activity assumes responsibility for creating new notes by
collecting user input and packing it into a return Bundle provided by the intent. This exercise
demonstrates:</em></p>
<ul>
<li><em>Constructing a new Activity and adding it to the Android manifest</em></li>
<li><em>Invoking another Activity asynchronously using <code>startActivityForResult()</code></em></li>
<li><em>Passing data between Activity in Bundle objects</em></li>
<li><em>How to use a more advanced screen layout</em></li>
<li><em>How to create a context menu</em></li>
</ul>
<div style="float:right;white-space:nowrap">
[<a href="notepad-ex1.html">Exercise 1</a>]
<span style="color:#BBB;">
[<a href="notepad-ex2.html" style="color:#DDD;">Exercise 2</a>]
</span>
[<a href="notepad-ex3.html">Exercise 3</a>]
[<a href="notepad-extra-credit.html">Extra Credit</a>]
</div>
<h2>Step 1</h2>
<p>Create a new Android project using the sources from <code>Notepadv2</code> under the
<code>NotepadCodeLab</code> folder, just like you did for the first exercise. If you see an error about
<code>AndroidManifest.xml</code>, or some problems related to an
<code>android.zip</code> file, right click on the project and select <strong>Android
Tools</strong> &gt; <strong>Fix Project Properties</strong>.</p>
<p>Open the <code>Notepadv2</code> project and take a look around:</p>
<ul>
<li>
Open and look at the <code>strings.xml</code> file under
<code>res/values</code> &mdash; there are several new strings which we will use
for our new functionality
</li>
<li>
Also, open and take a look at the top of the <code>Notepadv2</code> class,
you will notice several new constants have been defined along with a new <code>mNotesCursor</code>
field used to hold the cursor we are using.
</li>
<li>
Note also that the <code>fillData()</code> method has a few more comments and now uses
the new field to store the notes Cursor. The <code>onCreate()</code> method is
unchanged from the first exercise. Also notice that the member field used to store the
notes Cursor is now called <code>mNotesCursor</code>. The <code>m</code> denotes a member
field and is part of the Android coding style standards.
</li>
<li>
There are also a couple of new overridden methods
(<code>onCreateContextMenu()</code>, <code>onContextItemSelected()</code>,
<code>onListItemClick()</code> and <code>onActivityResult()</code>)
which we will be filling in below.
</li>
</ul>
<h2>Step 2</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<p>Context menus should always be used when performing actions upon specific elements in the UI.
When you register a View to a context menu, the context menu is revealed by performing a "long-click"
on the UI component (press and hold the touchscreen or highlight and hold down the selection key for about two seconds).</p>
</div>
</div>
<p>First, let's create the context menu that will allow users to delete individual notes.
Open the Notepadv2 class.</p>
<ol>
<li>In order for each list item in the ListView to register for the context menu, we call
<code>registerForContextMenu()</code> and pass it our ListView. So, at the very end of
the <code>onCreate()</code> method add this line:
<pre>registerForContextMenu(getListView());</pre>
<p>Because our Activity extends the ListActivity class, <code>getListView()</code> will return us
the local ListView object for the Activity. Now, each list item in this ListView will activate the
context menu.
<li>
Now fill in the <code>onCreateContextMenu()</code> method. This callback is similar to the other
menu callback used for the options menu. Here, we add just one line, which will add a menu item
to delete a note. Call <code>menu.add()</code> like so:
<pre>
public boolean onCreateContextMenu(Menu menu, View v
ContextMenuInfo menuInfo) {
super.onCreateContextMenu(menu, v, menuInfo);
menu.add(0, DELETE_ID, 0, R.string.menu_delete);
}</pre>
<p>The <code>onCreateContextMenu()</code> callback passes some other information in addition to the Menu object,
such as the View that has been triggered for the menu and
an extra object that may contain additional information about the object selected. However, we don't care about
these here, because we only have one kind of object in the Activity that uses context menus. In the next
step, we'll handle the menu item selection.</p>
</li>
</ol>
<h2>Step 3</h2>
<p>Now that the we've registered our ListView for a context menu and defined our context menu item, we need
to handle the callback when it is selected. For this, we need to identify the list ID of the
selected item, then delete it. So fill in the
<code>onContextItemSelected()</code> method like this:</p>
<pre>
public boolean onContextItemSelected(MenuItem item) {
switch(item.getItemId()) {
case DELETE_ID:
AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
mDbHelper.deleteNote(info.id);
fillData();
return true;
}
return super.onContextItemSelected(item);
}</pre>
<p>Here, we retrieve the {@link android.widget.AdapterView.AdapterContextMenuInfo AdapterContextMenuInfo}
with {@link android.view.MenuItem#getMenuInfo()}. The <var>id</var> field of this object tells us
the position of the item in the ListView. We then pass this to the <code>deleteNote()</code>
method of our NotesDbAdapter and the note is deleted. That's it for the context menu &mdash; notes
can now be deleted.</p>
<h2 style="clear:right;">Step 4</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Starting Other Activities</h2>
<p>In this example our Intent uses a class name specifically.
As well as
<a href="{@docRoot}resources/faq/commontasks.html#intentexamples">starting intents</a> in
classes we already know about, be they in our own application or another
application, we can also create Intents without knowing exactly which
application will handle it.</p>
<p>For example, we might want to open a page in a
browser, and for this we still use
an Intent. But instead of specifying a class to handle it, we use
a predefined Intent constant, and a content URI that describes what we
want to do. See {@link android.content.Intent
android.content.Intent} for more information.</p>
</div>
</div>
<p>Fill in the body of the <code>createNote()</code> method:
<p>Create a new <code>Intent</code> to create a note
(<code>ACTIVITY_CREATE</code>) using the <code>NoteEdit</code> class.
Then fire the Intent using the <code>startActivityForResult()</code> method
call:</p>
<pre style="overflow:auto">
Intent i = new Intent(this, NoteEdit.class);
startActivityForResult(i, ACTIVITY_CREATE);</pre>
<p>This form of the Intent call targets a specific class in our Activity, in this case
<code>NoteEdit</code>. Since the Intent class will need to communicate with the Android
operating system to route requests, we also have to provide a Context (<code>this</code>).</p>
<p>The <code>startActivityForResult()</code> method fires the Intent in a way that causes a method
in our Activity to be called when the new Activity is completed. The method in our Activity
that receives the callback is called
<code>onActivityResult()</code> and we will implement it in a later step. The other way
to call an Activity is using <code>startActivity()</code> but this is a "fire-and-forget" way
of calling it &mdash; in this manner, our Activity is not informed when the Activity is completed, and there is
no way to return result information from the called Activity with <code>startActivity()</code>.
<p>Don't worry about the fact that <code>NoteEdit</code> doesn't exist yet,
we will fix that soon. </p>
</li>
<h2>Step 5</h2>
<p>Fill in the body of the <code>onListItemClick()</code> override.</p>
<p><code>onListItemClick()</code> is a callback method that we'll override. It is called when
the user selects an item from the list. It is passed four parameters: the
<code>ListView</code> object it was invoked from, the <code>View</code>
inside the <code>ListView</code> that was clicked on, the
<code>position</code> in the list that was clicked, and the
<code>mRowId</code> of the item that was clicked. In this instance we can
ignore the first two parameters (we only have one <code>ListView</code> it
could be), and we ignore the <code>mRowId</code> as well. All we are
interested in is the <code>position</code> that the user selected. We use
this to get the data from the correct row, and bundle it up to send to
the <code>NoteEdit</code> Activity.</p>
<p>In our implementation of the callback, the method creates an
<code>Intent</code> to edit the note using
the <code>NoteEdit</code> class. It then adds data into the extras Bundle of
the Intent, which will be passed to the called Activity. We use it
to pass in the title and body text, and the <code>mRowId</code> for the note we are
editing. Finally, it will fire the Intent using the
<code>startActivityForResult()</code> method call. Here's the code that
belongs in <code>onListItemClick()</code>:</p>
<pre>
super.onListItemClick(l, v, position, id);
Cursor c = mNotesCursor;
c.moveToPosition(position);
Intent i = new Intent(this, NoteEdit.class);
i.putExtra(NotesDbAdapter.KEY_ROWID, id);
i.putExtra(NotesDbAdapter.KEY_TITLE, c.getString(
c.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE)));
i.putExtra(NotesDbAdapter.KEY_BODY, c.getString(
c.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY)));
startActivityForResult(i, ACTIVITY_EDIT);</pre>
<ul>
<li>
<code>putExtra()</code> is the method to add items into the extras Bundle
to pass in to intent invocations. Here, we are
using the Bundle to pass in the title, body and mRowId of the note we want to edit.
</li>
<li>
The details of the note are pulled out from our query Cursor, which we move to the
proper position for the element that was selected in the list, with
the <code>moveToPosition()</code> method.</li>
<li>With the extras added to the Intent, we invoke the Intent on the
<code>NoteEdit</code> class by passing <code>startActivityForResult()</code>
the Intent and the request code. (The request code will be
returned to <code>onActivityResult</code> as the <code>requestCode</code> parameter.)</li>
</ul>
<p class="note"><b>Note:</b> We assign the mNotesCursor field to a local variable at the
start of the method. This is done as an optimization of the Android code. Accessing a local
variable is much more efficient than accessing a field in the Dalvik VM, so by doing this
we make only one access to the field, and five accesses to the local variable, making the
routine much more efficient. It is recommended that you use this optimization when possible.</p>
<h2>Step 6</h2>
<p>The above <code>createNote()</code> and <code>onListItemClick()</code>
methods use an asynchronous Intent invocation. We need a handler for the callback, so here we fill
in the body of the <code>onActivityResult()</code>. </p>
<p><code>onActivityResult()</code> is the overridden method
which will be called when an Activity returns with a result. (Remember, an Activity
will only return a result if launched with <code>startActivityForResult</code>.) The parameters provided
to the callback are: </p>
<ul>
<li><code>requestCode</code> &mdash; the original request code
specified in the Intent invocation (either <code>ACTIVITY_CREATE</code> or
<code>ACTIVITY_EDIT</code> for us).
</li>
<li><code>resultCode</code> &mdash; the result (or error code) of the call, this
should be zero if everything was OK, but may have a non-zero code indicating
that something failed. There are standard result codes available, and you
can also create your own constants to indicate specific problems.
</li>
<li><code>intent</code> &mdash; this is an Intent created by the Activity returning
results. It can be used to return data in the Intent "extras."
</li>
</ul>
<p>The combination of <code>startActivityForResult()</code> and
<code>onActivityResult()</code> can be thought of as an asynchronous RPC
(remote procedure call) and forms the recommended way for an Activity to invoke
another and share services.</p>
<p>Here's the code that belongs in your <code>onActivityResult()</code>:</p>
<pre>
super.onActivityResult(requestCode, resultCode, intent);
Bundle extras = intent.getExtras();
switch(requestCode) {
case ACTIVITY_CREATE:
String title = extras.getString(NotesDbAdapter.KEY_TITLE);
String body = extras.getString(NotesDbAdapter.KEY_BODY);
mDbHelper.createNote(title, body);
fillData();
break;
case ACTIVITY_EDIT:
Long mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
if (mRowId != null) {
String editTitle = extras.getString(NotesDbAdapter.KEY_TITLE);
String editBody = extras.getString(NotesDbAdapter.KEY_BODY);
mDbHelper.updateNote(mRowId, editTitle, editBody);
}
fillData();
break;
}</pre>
<ul>
<li>
We are handling both the <code>ACTIVITY_CREATE</code> and
<code>ACTIVITY_EDIT</code> activity results in this method.
</li>
<li>
In the case of a create, we pull the title and body from the extras (retrieved from the
returned Intent) and use them to create a new note.
</li>
<li>
In the case of an edit, we pull the mRowId as well, and use that to update
the note in the database.
</li>
<li>
<code>fillData()</code> at the end ensures everything is up to date .
</li>
</ul>
<h2>Step 7</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>The Art of Layout</h2>
<p>The provided
note_edit.xml layout file is the most sophisticated one in the application we will be building,
but that doesn't mean it is even close to the kind of sophistication you will be likely to want
in real Android applications.</p>
<p>Creating a
good UI is part art and part science, and the rest is work. Mastery of <a
href="{@docRoot}guide/topics/ui/declaring-layout.html">Declaring Layout</a> is an essential part of creating
a good looking Android application.</p>
<p>Take a look at the
<a href="{@docRoot}resources/tutorials/views/index.html">Hello Views</a>
for some example layouts and how to use them. The ApiDemos sample project is also a
great resource from which to learn how to create different layouts.</p>
</div>
</div>
<p>Open the file <code>note_edit.xml</code> that has been provided and take a
look at it. This is the UI code for the Note Editor.</p>
<p>This is the most
sophisticated UI we have dealt with yet. The file is given to you to avoid
problems that may sneak in when typing the code. (The XML is very strict
about case sensitivity and structure, mistakes in these are the usual cause
of problems with layout.)</p>
<p>There is a new parameter used
here that we haven't seen before: <code>android:layout_weight</code> (in
this case set to use the value 1 in each case).</p>
<p><code>layout_weight</code> is used in LinearLayouts
to assign "importance" to Views within the layout. All Views have a default
<code>layout_weight</code> of zero, meaning they take up only as much room
on the screen as they need to be displayed. Assigning a value higher than
zero will split up the rest of the available space in the parent View, according
to the value of each View's <code>layout_weight</code> and its ratio to the
overall <code>layout_weight</code> specified in the current layout for this
and other View elements.</p>
<p>To give an example: let's say we have a text label
and two text edit elements in a horizontal row. The label has no
<code>layout_weight</code> specified, so it takes up the minimum space
required to render. If the <code>layout_weight</code> of each of the two
text edit elements is set to 1, the remaining width in the parent layout will
be split equally between them (because we claim they are equally important).
If the first one has a <code>layout_weight</code> of 1
and the second has a <code>layout_weight</code> of 2, then one third of the
remaining space will be given to the first, and two thirds to the
second (because we claim the second one is more important).</p>
<p>This layout also demonstrates how to nest multiple layouts
inside each other to achieve a more complex and pleasant layout. In this
example, a horizontal linear layout is nested inside the vertical one to
allow the title label and text field to be alongside each other,
horizontally.</p>
<h2 style="clear:right;">Step 8</h2>
<p>Create a <code>NoteEdit</code> class that extends
<code>android.app.Activity</code>.</p>
<p>This is the first time we will have
created an Activity without the Android Eclipse plugin doing it for us. When
you do so, the <code>onCreate()</code> method is not automatically
overridden for you. It is hard to imagine an Activity that doesn't override
the <code>onCreate()</code> method, so this should be the first thing you do.</p>
<ol>
<li>Right click on the <code>com.android.demo.notepad2</code> package
in the Package Explorer, and select <strong>New</strong> &gt; <strong>Class</strong> from the popup
menu.</li>
<li>Fill in <code>NoteEdit</code> for the <code>Name:</code> field in the
dialog.</li>
<li>In the <code>Superclass:</code> field, enter
<code>android.app.Activity</code> (you can also just type Activity and hit
Ctrl-Space on Windows and Linux or Cmd-Space on the Mac, to invoke code
assist and find the right package and class).</li>
<li>Click <strong>Finish</strong>.</li>
<li>In the resulting <code>NoteEdit</code> class, right click in the editor
window and select <strong>Source</strong> &gt; <strong>Override/Implement Methods...</strong></li>
<li>Scroll down through the checklist in the dialog until you see
<code>onCreate(Bundle)</code> &mdash; and check the box next to it.</li>
<li>Click <strong>OK</strong>.<p>The method should now appear in your class.</p></li>
</ol>
<h2>Step 9</h2>
<p>Fill in the body of the <code>onCreate()</code> method for <code>NoteEdit</code>.</p>
<p>This will set the title of our new Activity to say "Edit Note" (one
of the strings defined in <code>strings.xml</code>). It will also set the
content view to use our <code>note_edit.xml</code> layout file. We can then
grab handles to the title and body text edit views, and the confirm button,
so that our class can use them to set and get the note title and body,
and attach an event to the confirm button for when it is pressed by the
user.</p>
<p>We can then unbundle the values that were passed in to the Activity
with the extras Bundle attached to the calling Intent. We'll use them to pre-populate
the title and body text edit views so that the user can edit them.
Then we will grab and store the <code>mRowId</code> so we can keep
track of what note the user is editing.</p>
<ol>
<li>
Inside <code>onCreate()</code>, set up the layout:<br>
<pre>setContentView(R.layout.note_edit);</pre>
</li>
<li>
Find the edit and button components we need:
<p>These are found by the
IDs associated to them in the R class, and need to be cast to the right
type of <code>View</code> (<code>EditText</code> for the two text views,
and <code>Button</code> for the confirm button):</p>
<pre>
mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
Button confirmButton = (Button) findViewById(R.id.confirm);</pre>
<p>Note that <code>mTitleText</code> and <code>mBodyText</code> are member
fields (you need to declare them at the top of the class definition).</p>
</li>
<li>At the top of the class, declare a <code>Long mRowId</code> private field to store
the current <code>mRowId</code> being edited (if any).
</li>
<li>Continuing inside <code>onCreate()</code>,
add code to initialize the <code>title</code>, <code>body</code> and
<code>mRowId</code> from the extras Bundle in
the Intent (if it is present):<br>
<pre>
mRowId = null;
Bundle extras = getIntent().getExtras();
if (extras != null) {
String title = extras.getString(NotesDbAdapter.KEY_TITLE);
String body = extras.getString(NotesDbAdapter.KEY_BODY);
mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
if (title != null) {
mTitleText.setText(title);
}
if (body != null) {
mBodyText.setText(body);
}
}</pre>
<ul>
<li>
We are pulling the <code>title</code> and
<code>body</code> out of the
<code>extras</code> Bundle that was set from the
Intent invocation.
</li><li>
We also null-protect the text field setting (i.e., we don't want to set
the text fields to null accidentally).</li>
</ul>
</li>
<li>
Create an <code>onClickListener()</code> for the button:
<p>Listeners can be one of the more confusing aspects of UI
implementation, but
what we are trying to achieve in this case is simple. We want an
<code>onClick()</code> method to be called when the user presses the
confirm button, and use that to do some work and return the values
of the edited note to the Intent caller. We do this using something called
an anonymous inner class. This is a bit confusing to look at unless you
have seen them before, but all you really need to take away from this is
that you can refer to this code in the future to see how to create a
listener and attach it to a button. (Listeners are a common idiom
in Java development, particularly for user interfaces.) Here's the empty listener:<br>
<pre>
confirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
}
});</pre>
</li>
</ol>
<h2>Step 10</h2>
<p>Fill in the body of the <code>onClick()</code> method of the <code>OnClickListener</code> created in the last step.</p>
<p>This is the code that will be run when the user clicks on the
confirm button. We want this to grab the title and body text from the edit
text fields, and put them into the return Bundle so that they can be passed
back to the Activity that invoked this <code>NoteEdit</code> Activity. If the
operation is an edit rather than a create, we also want to put the
<code>mRowId</code> into the Bundle so that the
<code>Notepadv2</code> class can save the changes back to the correct
note.</p>
<ol>
<li>
Create a <code>Bundle</code> and put the title and body text into it using the
constants defined in Notepadv2 as keys:<br>
<pre>
Bundle bundle = new Bundle();
bundle.putString(NotesDbAdapter.KEY_TITLE, mTitleText.getText().toString());
bundle.putString(NotesDbAdapter.KEY_BODY, mBodyText.getText().toString());
if (mRowId != null) {
bundle.putLong(NotesDbAdapter.KEY_ROWID, mRowId);
}</pre>
</li>
<li>
Set the result information (the Bundle) in a new Intent and finish the Activity:
<pre>
Intent mIntent = new Intent();
mIntent.putExtras(bundle);
setResult(RESULT_OK, mIntent);
finish();</pre>
<ul>
<li>The Intent is simply our data carrier that carries our Bundle
(with the title, body and mRowId).</li>
<li>The <code>setResult()</code> method is used to set the result
code and return Intent to be passed back to the
Intent caller. In this case everything worked, so we return RESULT_OK for the
result code.</li>
<li>The <code>finish()</code> call is used to signal that the Activity
is done (like a return call). Anything set in the Result will then be
returned to the caller, along with execution control.</li>
</ul>
</li>
</ol>
<p>The full <code>onCreate()</code> method (plus supporting class fields) should
now look like this:</p>
<pre>
private EditText mTitleText;
private EditText mBodyText;
private Long mRowId;
&#64;Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.note_edit);
mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
Button confirmButton = (Button) findViewById(R.id.confirm);
mRowId = null;
Bundle extras = getIntent().getExtras();
if (extras != null) {
String title = extras.getString(NotesDbAdapter.KEY_TITLE);
String body = extras.getString(NotesDbAdapter.KEY_BODY);
mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
if (title != null) {
mTitleText.setText(title);
}
if (body != null) {
mBodyText.setText(body);
}
}
confirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Bundle bundle = new Bundle();
bundle.putString(NotesDbAdapter.KEY_TITLE, mTitleText.getText().toString());
bundle.putString(NotesDbAdapter.KEY_BODY, mBodyText.getText().toString());
if (mRowId != null) {
bundle.putLong(NotesDbAdapter.KEY_ROWID, mRowId);
}
Intent mIntent = new Intent();
mIntent.putExtras(bundle);
setResult(RESULT_OK, mIntent);
finish();
}
});
}</pre>
</li>
</ol>
<h2>Step 11</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>The All-Important Android Manifest File</h2>
<p>The AndroidManifest.xml file is the way in which Android sees your
application. This file defines the category of the application, where
it shows up (or even if it shows up) in the launcher or settings, what
activities, services, and content providers it defines, what intents it can
receive, and more. </p>
<p>For more information, see the reference document
<a href="{@docRoot}guide/topics/manifest/manifest-intro.html">The AndroidManifest.xml
File</a></p>
</div>
</div>
<p>Finally, the new Activity has to be defined in the manifest file:</p>
<p>Before the new Activity can be seen by Android, it needs its own
Activity entry in the <code>AndroidManifest.xml</code> file. This is to let
the system know that it is there and can be called. We could also specify
which IntentFilters the activity implements here, but we are going to skip
this for now and just let Android know that the Activity is
defined.</p>
<p>There is a Manifest editor included in the Eclipse plugin that makes it much easier
to edit the AndroidManifest file, and we will use this. If you prefer to edit the file directly
or are not using the Eclipse plugin, see the box at the end for information on how to do this
without using the new Manifest editor.<p>
<ol>
<li>Double click on the <code>AndroidManifest.xml</code> file in the package explorer to open it.
</li>
<li>Click the <strong>Application</strong> tab at the bottom of the Manifest editor.</li>
<li>Click <strong>Add...</strong> in the Application Nodes section.
<p>If you see a dialog with radiobuttons at the top, select the top radio button:
"Create a new element at the top level, in Application".</p></li>
<li>Make sure "(A) Activity" is selected in the selection pane of the dialog, and click <strong>OK</strong>.</li>
<li>Click on the new "Activity" node, in the Application Nodes section, then
type <code>.NoteEdit</code> into the <em>Name*</em>
field to the right. Press Return/Enter.</li>
</ol>
<p>The Android Manifest editor helps you add more complex entries into the AndroidManifest.xml
file, have a look around at some of the other options available (but be careful not to select
them otherwise they will be added to your Manifest). This editor should help you understand
and alter the AndroidManifest.xml file as you move on to more advanced Android applications.</p>
<p class="note">If you prefer to edit this file directly, simply open the
<code>AndroidManifest.xml</code> file and look at the source (use the
<code>AndroidManifest.xml</code> tab in the eclipse editor to see the source code directly).
Then edit the file as follows:<br>
<code>&lt;activity android:name=".NoteEdit" /&gt;</code><br><br>
This should be placed just below the line that reads:<br>
<code>&lt;/activity&gt;</code> for the <code>.Notepadv2</code> activity.</p>
<h2 style="clear:right;">Step 12</h2>
<p>Now Run it!</p>
<p>You should now be able to add real notes from
the menu, as well as delete an existing one. Notice that in order to delete, you must
first use the directional controls on the device to highlight the note.
Furthermore, selecting a note title from the list should bring up the note
editor to let you edit it. Press confirm when finished to save the changes
back to the database.
<h2>Solution and Next Steps</h2>
<p>You can see the solution to this exercise in <code>Notepadv2Solution</code>
from the zip file to compare with your own.</p>
<p>Now try editing a note, and then hitting the back button on the emulator
instead of the confirm button (the back button is below the menu button). You
will see an error come up. Clearly our application still has some problems.
Worse still, if you did make some changes and hit the back button, when you go
back into the notepad to look at the note you changed, you will find that all
your changes have been lost. In the next exercise we will fix these
problems.</p>
<p>
Once you are ready, move on to <a href="notepad-ex3.html">Tutorial
Exercise 3</a> where you will fix the problems with the back button and lost
edits by introducing a proper life cycle into the NoteEdit Activity.</p>

365
base/docs/html/guide/tutorials/notepad/notepad-ex3.jd Normal file
View File

@ -0,0 +1,365 @@
page.title=Notepad Exercise 3
parent.title=Notepad Tutorial
parent.link=index.html
@jd:body
<p><em>In this exercise, you will use life-cycle event callbacks to store and
retrieve application state data. This exercise demonstrates:</em></p>
<ul>
<li><em>Life-cycle events and how your application can use them</em></li>
<li><em>Techniques for maintaining application state</em></li>
</ul>
<div style="float:right;white-space:nowrap">
[<a href="notepad-ex1.html">Exercise 1</a>]
[<a href="notepad-ex2.html">Exercise 2</a>]
<span style="color:#BBB;">
[<a href="notepad-ex3.html" style="color:#BBB;">Exercise 3</a>]
</span>
[<a href="notepad-extra-credit.html">Extra Credit</a>]
</div>
<h2>Step 1</h2>
<p>Import <code>Notepadv3</code> into Eclipse. If you see an error about
<code>AndroidManifest.xml,</code> or some problems related to an Android zip
file, right click on the project and select <strong>Android Tools</strong> &gt;
<strong>Fix Project Properties</strong> from the popup menu. The starting point for this exercise is
exactly where we left off at the end of the Notepadv2. </p>
<p>The current application has some problems &mdash; hitting the back button when editing
causes a crash, and anything else that happens during editing will cause the
edits to be lost.</p>
<p>To fix this, we will move most of the functionality for creating and editing
the note into the NoteEdit class, and introduce a full life cycle for editing
notes.</p>
<ol>
<li>Remove the code in <code>NoteEdit</code> that parses the title and body
from the extras Bundle.
<p>Instead, we are going to use the <code>DBHelper</code> class
to access the notes from the database directly. All we need passed into the
NoteEdit Activity is a <code>mRowId</code> (but only if we are editing, if creating we pass
nothing). Remove these lines:</p>
<pre>
String title = extras.getString(NotesDbAdapter.KEY_TITLE);
String body = extras.getString(NotesDbAdapter.KEY_BODY);</pre>
</li>
<li>We will also get rid of the properties that were being passed in
the <code>extras</code> Bundle, which we were using to set the title
and body text edit values in the UI. So delete:
<pre>
if (title != null) {
mTitleText.setText(title);
}
if (body != null) {
mBodyText.setText(body);
}</pre>
</li>
</ol>
<h2>Step 2</h2>
<p>Create a class field for a <code>NotesDbAdapter</code> at the top of the NoteEdit class:</p>
<pre>&nbsp;&nbsp;&nbsp; private NotesDbAdapter mDbHelper;</pre>
<p>Also add an instance of <code>NotesDbAdapter</code> in the
<code>onCreate()</code> method (right below the <code>super.onCreate()</code> call):</p>
<pre>
&nbsp;&nbsp;&nbsp; mDbHelper = new NotesDbAdapter(this);<br>
&nbsp;&nbsp;&nbsp; mDbHelper.open();</pre>
<h2>Step 3</h2>
<p>In <code>NoteEdit</code>, we need to check the <var>savedInstanceState</var> for the
<code>mRowId</code>, in case the note
editing contains a saved state in the Bundle, which we should recover (this would happen
if our Activity lost focus and then restarted).</p>
<ol>
<li>
Replace the code that currently initializes the <code>mRowId</code>:<br>
<pre>
mRowId = null;
Bundle extras = getIntent().getExtras();
if (extras != null) {
mRowId = extras.getLong(NotesDbAdapter.KEY_ROWID);
}
</pre>
with this:
<pre>
mRowId = (savedInstanceState == null) ? null :
(Long) savedInstanceState.getSerializable(NotesDbAdapter.KEY_ROWID);
if (mRowId == null) {
Bundle extras = getIntent().getExtras();
mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID)
: null;
}
</pre>
</li>
<li>
Note the null check for <code>savedInstanceState</code>, and we still need to load up
<code>mRowId</code> from the <code>extras</code> Bundle if it is not
provided by the <code>savedInstanceState</code>. This is a ternary operator shorthand
to safely either use the value or null if it is not present.
</li>
<li>
Note the use of <code>Bundle.getSerializable()</code> instead of
<code>Bundle.getLong()</code>. The latter encoding returns a <code>long</code> primitive and
so can not be used to represent the case when <code>mRowId</code> is <code>null</code>.
</li>
</ol>
<h2>Step 4</h2>
<p>Next, we need to populate the fields based on the <code>mRowId</code> if we
have it:</p>
<pre>populateFields();</pre>
<p>This goes before the <code>confirmButton.setOnClickListener()</code> line.
We'll define this method in a moment.</p>
<h2>Step 5</h2>
<p>Get rid of the Bundle creation and Bundle value settings from the
<code>onClick()</code> handler method. The Activity no longer needs to
return any extra information to the caller. And because we no longer have
an Intent to return, we'll use the shorter version
of <code>setResult()</code>:</p>
<pre>
public void onClick(View view) {
setResult(RESULT_OK);
finish();
}</pre>
<p>We will take care of storing the updates or new notes in the database
ourselves, using the life-cycle methods.</p>
<p>The whole <code>onCreate()</code> method should now look like this:</p>
<pre>
super.onCreate(savedInstanceState);
mDbHelper = new NotesDbAdapter(this);
mDbHelper.open();
setContentView(R.layout.note_edit);
mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
Button confirmButton = (Button) findViewById(R.id.confirm);
mRowId = (savedInstanceState == null) ? null :
(Long) savedInstanceState.getSerializable(NotesDbAdapter.KEY_ROWID);
if (mRowId == null) {
Bundle extras = getIntent().getExtras();
mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID)
: null;
}
populateFields();
confirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
setResult(RESULT_OK);
finish();
}
});</pre>
<h2>Step 6</h2>
<p>Define the <code>populateFields()</code> method.</p>
<pre>
private void populateFields() {
if (mRowId != null) {
Cursor note = mDbHelper.fetchNote(mRowId);
startManagingCursor(note);
mTitleText.setText(note.getString(
note.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE)));
mBodyText.setText(note.getString(
note.getColumnIndexOrThrow(NotesDbAdapter.KEY_BODY)));
}
}</pre>
<p>This method uses the <code>NotesDbAdapter.fetchNote()</code> method to find the right note to
edit, then it calls <code>startManagingCursor()</code> from the <code>Activity</code> class, which
is an Android convenience method provided to take care of the Cursor life-cycle. This will release
and re-create resources as dictated by the Activity life-cycle, so we don't need to worry about
doing that ourselves. After that, we just look up the title and body values from the Cursor
and populate the View elements with them.</p>
<h2>Step 7</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h2>Why handling life-cycle events is important</h2>
<p>If you are used to always having control in your applications, you
might not understand why all this life-cycle work is necessary. The reason
is that in Android, you are not in control of your Activity, the
operating system is!</p>
<p>As we have already seen, the Android model is based around activities
calling each other. When one Activity calls another, the current Activity
is paused at the very least, and may be killed altogether if the
system starts to run low on resources. If this happens, your Activity will
have to store enough state to come back up later, preferably in the same
state it was in when it was killed.</p>
<p>
Android has a <a href="{@docRoot}guide/topics/fundamentals.html#lcycles">well-defined life
cycle</a>.
Lifecycle events can happen even if you are not handing off control to
another Activity explicitly. For example, perhaps a call comes in to the
handset. If this happens, and your Activity is running, it will be swapped
out while the call Activity takes over.</p>
</div>
</div>
<p>Still in the <code>NoteEdit</code> class, we now override the methods
<code>onSaveInstanceState()</code>, <code>onPause()</code> and
<code>onResume()</code>. These are our life-cycle methods
(along with <code>onCreate()</code> which we already have).</p>
<p><code>onSaveInstanceState()</code> is called by Android if the
Activity is being stopped and <strong>may be killed before it is
resumed!</strong> This means it should store any state necessary to
re-initialize to the same condition when the Activity is restarted. It is
the counterpart to the <code>onCreate()</code> method, and in fact the
<code>savedInstanceState</code> Bundle passed in to <code>onCreate()</code> is the same
Bundle that you construct as <code>outState</code> in the
<code>onSaveInstanceState()</code> method.</p>
<p><code>onPause()</code> and <code>onResume()</code> are also
complimentary methods. <code>onPause()</code> is always called when the
Activity ends, even if we instigated that (with a <code>finish()</code> call for example).
We will use this to save the current note back to the database. Good
practice is to release any resources that can be released during an
<code>onPause()</code> as well, to take up less resources when in the
passive state. <code>onResume()</code> will call our <code>populateFields()</code> method
to read the note out of the database again and populate the fields.</p>
<p>So, add some space after the <code>populateFields()</code> method
and add the following life-cycle methods:</p>
<ol type="a">
<li><code>
onSaveInstanceState()</code>:
<pre>
&#64;Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
saveState();
outState.putSerializable(NotesDbAdapter.KEY_ROWID, mRowId);
}</pre>
<p>We'll define <code>saveState()</code> next.</p>
</li>
<li><code>
onPause()</code>:
<pre>
&#64;Override
protected void onPause() {
super.onPause();
saveState();
}</pre>
</li>
<li><code>
onResume()</code>:
<pre>
&#64;Override
protected void onResume() {
super.onResume();
populateFields();
}</pre>
</li>
</ol>
<p>Note that <code>saveState()</code> must be called in both <code>onSaveInstanceState()</code>
and <code>onPause()</code> to ensure that the data is saved. This is because there is no
guarantee that <code>onSaveInstanceState()</code> will be called and because when it <em>is</em>
called, it is called before <code>onPause()</code>.</p>
<h2 style="clear:right;">Step 8</h2>
<p>Define the <code>saveState()</code> method to put the data out to the
database.</p>
<pre>
private void saveState() {
String title = mTitleText.getText().toString();
String body = mBodyText.getText().toString();
if (mRowId == null) {
long id = mDbHelper.createNote(title, body);
if (id > 0) {
mRowId = id;
}
} else {
mDbHelper.updateNote(mRowId, title, body);
}
}</pre>
<p>Note that we capture the return value from <code>createNote()</code> and if a valid row ID is
returned, we store it in the <code>mRowId</code> field so that we can update the note in future
rather than create a new one (which otherwise might happen if the life-cycle events are
triggered).</p>
<h2 style="clear:right;">Step 9</h2>
<p>Now pull out the previous handling code from the
<code>onActivityResult()</code> method in the <code>Notepadv3</code>
class.</p>
<p>All of the note retrieval and updating now happens within the
<code>NoteEdit</code> life cycle, so all the <code>onActivityResult()</code>
method needs to do is update its view of the data, no other work is
necessary. The resulting method should look like this:</p>
<pre>
&#64;Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
super.onActivityResult(requestCode, resultCode, intent);
fillData();
}</pre>
<p>Because the other class now does the work, all this has to do is refresh
the data.</p>
<h2>Step 10</h2>
<p>Also remove the lines which set the title and body from the
<code>onListItemClick()</code> method (again they are no longer needed,
only the <code>mRowId</code> is):</p>
<pre>
Cursor c = mNotesCursor;
c.moveToPosition(position);</pre>
<br>
and also remove:
<br>
<pre>
i.putExtra(NotesDbAdapter.KEY_TITLE, c.getString(
c.getColumnIndex(NotesDbAdapter.KEY_TITLE)));
i.putExtra(NotesDbAdapter.KEY_BODY, c.getString(
c.getColumnIndex(NotesDbAdapter.KEY_BODY)));</pre>
<br>
so that all that should be left in that method is:
<br>
<pre>
super.onListItemClick(l, v, position, id);
Intent i = new Intent(this, NoteEdit.class);
i.putExtra(NotesDbAdapter.KEY_ROWID, id);
startActivityForResult(i, ACTIVITY_EDIT);</pre>
<p>You can also now remove the mNotesCursor field from the class, and set it back to using
a local variable in the <code>fillData()</code> method:
<br><pre>
Cursor notesCursor = mDbHelper.fetchAllNotes();</pre></p>
<p>Note that the <code>m</code> in <code>mNotesCursor</code> denotes a member field, so when we
make <code>notesCursor</code> a local variable, we drop the <code>m</code>. Remember to rename the
other occurrences of <code>mNotesCursor</code> in your <code>fillData()</code> method.
</ol>
<p>
Run it! (use <em>Run As -&gt; Android Application</em> on the project right
click menu again)</p>
<h2>Solution and Next Steps</h2>
<p>You can see the solution to this exercise in <code>Notepadv3Solution</code>
from
the zip file to compare with your own.</p>
<p>
When you are ready, move on to the <a href="notepad-extra-credit.html">Tutorial
Extra Credit</a> exercise, where you can use the Eclipse debugger to
examine the life-cycle events as they happen.</p>

70
base/docs/html/guide/tutorials/notepad/notepad-extra-credit.jd Normal file
View File

@ -0,0 +1,70 @@
page.title=Notepad Extra Credit
parent.title=Notepad Tutorial
parent.link=index.html
@jd:body
<p><em>In this exercise, you will use the debugger to look at the work you did
in Exercise 3. This exercise demonstrates:</em></p>
<ul>
<li><em>How to set breakpoints to observe execution</em> </li>
<li><em>How to run your application in debug mode</code></em></li>
</ul>
<div style="float:right;white-space:nowrap">
[<a href="notepad-ex1.html">Exercise 1</a>]
[<a href="notepad-ex2.html">Exercise 2</a>]
[<a href="notepad-ex3.html">Exercise 3</a>]
<span style="color:#BBB;">
[<a href="notepad-extra-credit.html" style="color:#BBB;">Extra Credit</a>]
</span>
</div>
<h2>Step 1</h2>
<p>Using the working <code>Notepadv3</code>, put breakpoints in the code at the
beginning of the <code>onCreate()</code>, <code>onPause()</code>,
<code>onSaveInstanceState()</code> and <code>onResume()</code> methods in the
<code>NoteEdit</code> class (if you are not familiar with Eclipse, just
right click in the narrow grey border on the left of the edit window at the
line you want a breakpoint, and select <em>Toggle Breakpoint</em>, you
should see a blue dot appear).</p>
<h2>Step 2</h2>
<p>Now start the notepad demo in debug mode:</p>
<ol type="a">
<li>
Right click on the <code>Notepadv3</code> project and from the Debug menu
select <em>Debug As -&gt; Android Application.</em></li>
<li>
The Android emulator should say <em>"waiting for debugger to connect"</em>
briefly and then run the application.</li>
<li>
If it gets stuck on the waiting... screen, quit the emulator and Eclipse,
from the command line do an <code>adb kill-server</code>, and then restart
Eclipse and try again.</li></ol>
<h2>Step 3</h2>
<p>When you edit or create a new note you should see the breakpoints getting
hit and the execution stopping.</p>
<h2>Step 4</h2>
<p>Hit the Resume button to let execution continue (yellow rectangle with a
green triangle to its right in the Eclipse toolbars near the top).</p>
<h2>Step 5</h2>
<p>Experiment a bit with the confirm and back buttons, and try pressing Home and
making other mode changes. Watch what life-cycle events are generated and
when.</p>
<p>The Android Eclipse plugin not only offers excellent debugging support for
your application development, but also superb profiling support. You can also
try using <a href="{@docRoot}guide/developing/tools/traceview.html">Traceview</a> to profile your application. If your application is running too slow, this can help you
find the bottlenecks and fix them.</p>

143
base/docs/html/guide/tutorials/notepad/notepad-index.jd Normal file
View File

@ -0,0 +1,143 @@
page.title=Notepad Tutorial
@jd:body
<p>The tutorial in this section gives you a &quot;hands-on&quot; introduction
to the Android framework and the tools you use to build applications on it.
Starting from a preconfigured project file, it guides you through the process of
developing a simple notepad application and provides concrete examples of how to
set up the project, develop the application logic and user interface, and then
compile and run the application. </p>
<p>The tutorial presents the notepad application development as a set of
exercises (see below), each consisting of several steps. You can follow along
with the steps in each exercise and gradually build up and refine your
application. The exercises explain each step in detail and provide all the
sample code you need to complete the application. </p>
<p>When you are finished with the tutorial, you will have created a functioning
Android application and learned in depth about many of the most important
concepts in Android development. If you want to add more complex features to
your application, you can examine the code in an alternative implementation
of a notepad application, in the
<a href="{@docRoot}samples/NotePad/index.html">Sample Code</a> documentation. </p>
<a name="who"></a>
<h2>Who Should Use this Tutorial</h2>
<p>This tutorial is designed for experienced developers, especially those with
knowledge of the Java programming language. If you haven't written Java
applications before, you can still use the tutorial, but you might need to work
at a slower pace. </p>
<p>The tutorial assumes that you have some familiarity with the basic Android
application concepts and terminology. If you aren't yet familiar with those, you
should read <a href="{@docRoot}intro/anatomy.html">Overview of an Android
Application</a> before continuing. </p>
<p>Also note that this tutorial uses
the Eclipse development environment, with the Android plugin installed. If you
are not using Eclipse, you can follow the exercises and build the application,
but you will need to determine how to accomplish the Eclipse-specific
steps in your environment. </p>
<a name="preparing"></a>
<h2>Preparing for the Exercises</h2>
<p>This tutorial builds on the information provided in the <a
href="{@docRoot}intro/installing.html">Installing the SDK</a> and <a
href="{@docRoot}intro/hello-android.html">Hello Android</a>
documents, which explain in detail how to set up your development environment
for building Android applications. Before you start this tutorial, you should
read both these documents, have the SDK installed, and your work environment set up.</p>
<p>To prepare for this lesson:</p>
<ol>
<li>Download the <a href="codelab/NotepadCodeLab.zip">project
exercises archive (.zip)</a></li>
<li>Unpack the archive file to a suitable location on your machine</li>
<li>Open the <code>NotepadCodeLab</code> folder</li>
</ol>
<p>Inside the <code>NotepadCodeLab</code> folder, you should see six project
files: <code>Notepadv1</code>,
<code>Notepadv2</code>, <code>Notepadv3</code>,
<code>Notepadv1Solution</code>, <code>Notepadv2Solution</code>
and <code>Notepadv3Solution</code>. The <code>Notepadv#</code> projects are
the starting points for each of the exercises, while the
<code>Notepadv#Solution</code> projects are the exercise
solutions. If you are having trouble with a particular exercise, you
can compare your current work against the exercise solution.</p>
<a name="exercises"></a>
<h2> Exercises</h2>
<p>The table below lists the tutorial exercises and describes the development
areas that each covers. Each exercise assumes that you have completed any
previous exercises.</p>
<table border="0" style="padding:4px;spacing:2px;" summary="This
table lists the
tutorial examples and describes what each covers. ">
<tr>
<th width="120"><a href="{@docRoot}intro/tutorial-ex1.html">Exercise
1</a></th>
<td>Start here. Construct a simple notes list that lets the user add new notes but not
edit them. Demonstrates the basics of <code>ListActivity</code> and creating
and handling
menu options. Uses a SQLite database to store the notes.</td>
</tr>
<tr>
<th><a href="{@docRoot}intro/tutorial-ex2.html">Exercise 2</a></th>
<td>Add a second Activity to the
application. Demonstrates constructing a
new Activity, adding it to the Android manifest, passing data between the
activities, and using more advanced screen layout. Also shows how to
invoke another Activity to return a result, using
<code>startActivityForResult()</code>.</td>
</tr>
<tr>
<th><a href="{@docRoot}intro/tutorial-ex3.html">Exercise 3</a></th>
<td>Add handling of life-cycle events to
the application, to let it
maintain application state across the life cycle. </td>
</tr>
<tr>
<th><a href="{@docRoot}intro/tutorial-extra-credit.html">Extra
Credit</a></th>
<td>Demonstrates how to use the Eclipse
debugger and how you can use it to
view life-cycle events as they are generated. This section is optional but
highly recommended.</td>
</tr>
</table>
<a name="other"></a>
<h2>Other Resources and Further Learning</h2>
<ul>
<li>For a lighter but broader introduction to concepts not covered in the
tutorial,
take a look at <a href="{@docRoot}kb/commontasks.html">Common Android Tasks</a>.</li>
<li>The Android SDK includes a variety of fully functioning sample applications
that make excellent opportunities for further learning. You can find the sample
applications in the <code>samples/</code> directory of your downloaded SDK.</li>
<li>This tutorial draws from the full Notepad application included in the
<code>samples/</code> directory of the SDK, though it does not match it exactly.
When you are done with the tutorial,
it is highly recommended that you take a closer look at this version of the Notepad
application,
as it demonstrates a variety of interesting additions for your application,
such as:</li>
<ul>
<li>Setting up a custom striped list for the list of notes.</li>
<li>Creating a custom text edit view that overrides the <code>draw()</code>
method to
make it look like a lined notepad.</li>
<li>Implementing a full <code>ContentProvider</code> for notes.</li>
<li>Reverting and discarding edits instead of just automatically saving
them.</li>
</ul>
</ul>

116
base/docs/html/guide/tutorials/views/hello-autocomplete.jd Normal file
View File

@ -0,0 +1,116 @@
page.title=Hello, AutoCompleteTextView
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>{@link android.widget.AutoCompleteTextView} is an implementation of the EditText widget that will provide
auto-complete suggestions as the user types. The suggestions are extracted from a collection of strings.</p>
<ol>
<li>Start a new project/Activity called HelloAutoComplete.</li>
<li>Open the layout file.
Make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
&lt;TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Country" />
&lt;AutoCompleteTextView android:id="@+id/edit"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
&lt;/LinearLayout>
</pre>
</li>
<li>Open HelloAutoComplete.java and insert the following as the <code>onCreate</code> method:
<pre>
&#64;Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
AutoCompleteTextView textView = (AutoCompleteTextView) findViewById(R.id.edit);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_dropdown_item_1line, COUNTRIES);
textView.setAdapter(adapter);
}
</pre>
<p>Here, we create an AutoCompleteTextView from our layout. We then
create an {@link android.widget.ArrayAdapter} that binds a <code>simple_dropdown_item_1line</code>
layout item to each entry in the <code>COUNTRIES</code> array (which we'll add next).
The last part sets the ArrayAdapter to associate with our AutoCompleteTextView.</p>
</li>
<li>After the <code>onCreate()</code> method, add the String array:
<pre>
static final String[] COUNTRIES = new String[] {
"Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra",
"Angola", "Anguilla", "Antarctica", "Antigua and Barbuda", "Argentina",
"Armenia", "Aruba", "Australia", "Austria", "Azerbaijan",
"Bahrain", "Bangladesh", "Barbados", "Belarus", "Belgium",
"Belize", "Benin", "Bermuda", "Bhutan", "Bolivia",
"Bosnia and Herzegovina", "Botswana", "Bouvet Island", "Brazil", "British Indian Ocean Territory",
"British Virgin Islands", "Brunei", "Bulgaria", "Burkina Faso", "Burundi",
"Cote d'Ivoire", "Cambodia", "Cameroon", "Canada", "Cape Verde",
"Cayman Islands", "Central African Republic", "Chad", "Chile", "China",
"Christmas Island", "Cocos (Keeling) Islands", "Colombia", "Comoros", "Congo",
"Cook Islands", "Costa Rica", "Croatia", "Cuba", "Cyprus", "Czech Republic",
"Democratic Republic of the Congo", "Denmark", "Djibouti", "Dominica", "Dominican Republic",
"East Timor", "Ecuador", "Egypt", "El Salvador", "Equatorial Guinea", "Eritrea",
"Estonia", "Ethiopia", "Faeroe Islands", "Falkland Islands", "Fiji", "Finland",
"Former Yugoslav Republic of Macedonia", "France", "French Guiana", "French Polynesia",
"French Southern Territories", "Gabon", "Georgia", "Germany", "Ghana", "Gibraltar",
"Greece", "Greenland", "Grenada", "Guadeloupe", "Guam", "Guatemala", "Guinea", "Guinea-Bissau",
"Guyana", "Haiti", "Heard Island and McDonald Islands", "Honduras", "Hong Kong", "Hungary",
"Iceland", "India", "Indonesia", "Iran", "Iraq", "Ireland", "Israel", "Italy", "Jamaica",
"Japan", "Jordan", "Kazakhstan", "Kenya", "Kiribati", "Kuwait", "Kyrgyzstan", "Laos",
"Latvia", "Lebanon", "Lesotho", "Liberia", "Libya", "Liechtenstein", "Lithuania", "Luxembourg",
"Macau", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali", "Malta", "Marshall Islands",
"Martinique", "Mauritania", "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova",
"Monaco", "Mongolia", "Montserrat", "Morocco", "Mozambique", "Myanmar", "Namibia",
"Nauru", "Nepal", "Netherlands", "Netherlands Antilles", "New Caledonia", "New Zealand",
"Nicaragua", "Niger", "Nigeria", "Niue", "Norfolk Island", "North Korea", "Northern Marianas",
"Norway", "Oman", "Pakistan", "Palau", "Panama", "Papua New Guinea", "Paraguay", "Peru",
"Philippines", "Pitcairn Islands", "Poland", "Portugal", "Puerto Rico", "Qatar",
"Reunion", "Romania", "Russia", "Rwanda", "Sqo Tome and Principe", "Saint Helena",
"Saint Kitts and Nevis", "Saint Lucia", "Saint Pierre and Miquelon",
"Saint Vincent and the Grenadines", "Samoa", "San Marino", "Saudi Arabia", "Senegal",
"Seychelles", "Sierra Leone", "Singapore", "Slovakia", "Slovenia", "Solomon Islands",
"Somalia", "South Africa", "South Georgia and the South Sandwich Islands", "South Korea",
"Spain", "Sri Lanka", "Sudan", "Suriname", "Svalbard and Jan Mayen", "Swaziland", "Sweden",
"Switzerland", "Syria", "Taiwan", "Tajikistan", "Tanzania", "Thailand", "The Bahamas",
"The Gambia", "Togo", "Tokelau", "Tonga", "Trinidad and Tobago", "Tunisia", "Turkey",
"Turkmenistan", "Turks and Caicos Islands", "Tuvalu", "Virgin Islands", "Uganda",
"Ukraine", "United Arab Emirates", "United Kingdom",
"United States", "United States Minor Outlying Islands", "Uruguay", "Uzbekistan",
"Vanuatu", "Vatican City", "Venezuela", "Vietnam", "Wallis and Futuna", "Western Sahara",
"Yemen", "Yugoslavia", "Zambia", "Zimbabwe"
};
</pre>
<p>This is the list of suggestions that will be offered as the user types into the
AutoCompleteTextView.</p>
</li>
<li>Now run it.</li>
</ol>
<p>As you type, you should see something like this:</p>
<img src="images/hello-autocomplete.png" width="150px" />
<h3>References</h3>
<ul>
<li>{@link android.R.layout}</li>
<li>{@link android.widget.ArrayAdapter}</li>
<li>{@link android.widget.AutoCompleteTextView}</li>
</ul>

151
base/docs/html/guide/tutorials/views/hello-datepicker.jd Normal file
View File

@ -0,0 +1,151 @@
page.title=Hello, DatePicker
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.DatePicker} is a widget that allows the user to select a month, day and year.</p>
<ol>
<li>Start a new project/Activity called HelloDatePicker.</li>
<li>Open the layout file and make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
&lt;TextView android:id="@+id/dateDisplay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""/>
&lt;Button android:id="@+id/pickDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Change the date"/>
&lt;/LinearLayout>
</pre>
<p>For the layout, we're using a vertical LinearLayout, with a {@link android.widget.TextView} that
will display the date and a {@link android.widget.Button} that will initiate the DatePicker dialog.
With this layout, the TextView will sit above the Button.
The text value in the TextView is set empty, as it will be filled
with the current date when our Activity runs.</p>
</li>
<li>Open HelloDatePicker.java. Insert the following to the HelloDatePicker class:
<pre>
private TextView mDateDisplay;
private Button mPickDate;
private int mYear;
private int mMonth;
private int mDay;
static final int DATE_DIALOG_ID = 0;
&#64;Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// capture our View elements
mDateDisplay = (TextView) findViewById(R.id.dateDisplay);
mPickDate = (Button) findViewById(R.id.pickDate);
// add a click listener to the button
mPickDate.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
showDialog(DATE_DIALOG_ID);
}
});
// get the current date
final Calendar c = Calendar.getInstance();
mYear = c.get(Calendar.YEAR);
mMonth = c.get(Calendar.MONTH);
mDay = c.get(Calendar.DAY_OF_MONTH);
// display the current date
updateDisplay();
}
</pre>
<p class="note"><strong>Tip:</strong> Press Ctrl(or Cmd) + Shift + O to import all needed packages.</p>
<p>We start by instantiating variables for our Views and date fields.
The <code>DATE_DIALOG_ID</code> is a static integer that uniquely identifies the Dialog. In the
<code>onCreate()</code> method, we get prepared by setting the layout and capturing the View elements.
Then we create an on-click listener for the Button, so that when it is clicked it will
show our DatePicker dialog. The <code>showDialog()</code> method will pop-up the date picker dialog
by calling the <code>onCreateDialog()</code> callback method
(which we'll define in the next section). We then create an
instance of {@link java.util.Calendar} and get the current year, month and day. Finally, we call
<code>updateDisplay()</code>&mdash;our own method (defined later) that will fill the TextView.</p>
</li>
<li>After the <code>onCreate()</code> method, add the <code>onCreateDialog()</code> callback method
(which is called by <code>showDialog()</code>)
<pre>
&#64;Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_DIALOG_ID:
return new DatePickerDialog(this,
mDateSetListener,
mYear, mMonth, mDay);
}
return null;
}
</pre>
<p>This method is passed the identifier we gave <code>showDialog()</code> and initializes
the DatePicker to the date we retrieved from our Calendar instance.</p>
</li>
<li>Following that, add the <code>updateDisplay()</code> method:
<pre>
// updates the date we display in the TextView
private void updateDisplay() {
mDateDisplay.setText(
new StringBuilder()
// Month is 0 based so add 1
.append(mMonth + 1).append("-")
.append(mDay).append("-")
.append(mYear).append(" "));
}
</pre>
<p>This uses the member date values to write the date to our TextView.</p>
</li>
<li>Finally, add a listener that will be called when the user sets a new date:
<pre>
// the callback received when the user "sets" the date in the dialog
private DatePickerDialog.OnDateSetListener mDateSetListener =
new DatePickerDialog.OnDateSetListener() {
public void onDateSet(DatePicker view, int year,
int monthOfYear, int dayOfMonth) {
mYear = year;
mMonth = monthOfYear;
mDay = dayOfMonth;
updateDisplay();
}
};
</pre>
<p>This <code>OnDateSetListener</code> method listens for when the user is done setting the date
(clicks the "Set" button). At that time, this fires and we update our member fields with
the new date defined by the user and update our TextView by calling <code>updateDisplay()</code>.</p>
</li>
<li>Now run it.</li>
</ol>
<p>When you press the "Change the date" button, you should see the following:</p>
<img src="images/hello-datepicker.png" width="150px" />
<h3>References</h3>
<ul>
<li>{@link android.widget.DatePicker}</li>
<li>{@link android.widget.Button}</li>
<li>{@link android.widget.TextView}</li>
<li>{@link java.util.Calendar}</li>
</ul>

262
base/docs/html/guide/tutorials/views/hello-formstuff.jd Normal file
View File

@ -0,0 +1,262 @@
page.title=Hello, Form Stuff
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>This page introduces a variety of widgets, like image buttons,
text fields, checkboxes and radio buttons.</p>
<ol>
<li>Start a new project/Activity called HelloFormStuff.</li>
<li>Your layout file should have a basic LinearLayout:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
&lt;/LinearLayout>
</pre>
<p>For each widget you want to add, just put the respective View inside here.</p>
</li>
</ol>
<p class="note"><strong>Tip:</strong> As you add new Android code, press Ctrl(or Cmd) + Shift + O
to import all needed packages.</p>
<h2>ImageButton</h2>
<p>A button with a custom image on it.
We'll make it display a message when pressed.</p>
<ol>
<li><img src="images/android.png" align="right"/>
Drag the Android image on the right (or your own image) into the
res/drawable/ directory of your project.
We'll use this for the button.</li>
<li>Open the layout file and, inside the LinearLayout, add the {@link android.widget.ImageButton} element:
<pre>
&lt;ImageButton
android:id="@+id/android_button"
android:layout_width="100dip"
android:layout_height="wrap_content"
android:src="@drawable/android" />
</pre>
<p>The source of the button
is from the res/drawable/ directory, where we've placed the android.png.</p>
<p class="note"><strong>Tip:</strong> You can also reference some of the many built-in
images from the Android {@link android.R.drawable} resources,
like <code>ic_media_play</code>, for a "play" button image. To do so, change the source
attribute to <code>android:src="@android:drawable/ic_media_play"</code>.</p>
</li>
<li>To make the button to actually do something, add the following
code at the end of the <code>onCreate()</code> method:
<pre>
final ImageButton button = (ImageButton) findViewById(R.id.android_button);
button.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// Perform action on clicks
Toast.makeText(HelloFormStuff.this, "Beep Bop", Toast.LENGTH_SHORT).show();
}
});
</pre>
<p>This captures our ImageButton from the layout, then adds an on-click listener to it.
The {@link android.view.View.OnClickListener} must define the <code>onClick()</code> method, which
defines the action to be made when the button is clicked. Here, we show a
{@link android.widget.Toast} message when clicked.</p>
</li>
<li>Run it.</li>
</ol>
<h2>EditText</h2>
<p>A text field for user input. We'll make it display the text entered so far when the "Enter" key is pressed.</p>
<ol>
<li>Open the layout file and, inside the LinearLayout, add the {@link android.widget.EditText} element:
<pre>
&lt;EditText
android:id="@+id/edittext"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</pre>
</li>
<li>To do something with the text that the user enters, add the following code
to the end of the <code>onCreate()</code> method:
<pre>
final EditText edittext = (EditText) findViewById(R.id.edittext);
edittext.setOnKeyListener(new OnKeyListener() {
public boolean onKey(View v, int keyCode, KeyEvent event) {
if ((event.getAction() == KeyEvent.ACTION_DOWN) && (keyCode == KeyEvent.KEYCODE_ENTER)) {
// Perform action on key press
Toast.makeText(HelloFormStuff.this, edittext.getText(), Toast.LENGTH_SHORT).show();
return true;
}
return false;
}
});
</pre>
<p>This captures our EditText element from the layout, then adds an on-key listener to it.
The {@link android.view.View.OnKeyListener} must define the <code>onKey()</code> method, which
defines the action to be made when a key is pressed. In this case, we want to listen for the
Enter key (when pressed down), then pop up a {@link android.widget.Toast} message with the
text from the EditText field. Be sure to return <var>true</var> after the event is handled,
so that the event doesn't bubble-up and get handled by the View (which would result in a
carriage return in the text field).</p>
<li>Run it.</li>
</ol>
<h2>CheckBox</h2>
<p>A checkbox for selecting items. We'll make it display the the current state when pressed.</p>
<ol>
<li>Open the layout file and, inside the LinearLayout, add the {@link android.widget.CheckBox} element:
<pre>
&lt;CheckBox android:id="@+id/checkbox"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="check it out" />
</pre>
</li>
<li>To do something when the state is changed, add the following code
to the end of the <code>onCreate()</code> method:
<pre>
final CheckBox checkbox = (CheckBox) findViewById(R.id.checkbox);
checkbox.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// Perform action on clicks
if (checkbox.isChecked()) {
Toast.makeText(HelloFormStuff.this, "Selected", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(HelloFormStuff.this, "Not selected", Toast.LENGTH_SHORT).show();
}
}
});
</pre>
<p>This captures our CheckBox element from the layout, then adds an on-click listener to it.
The {@link android.view.View.OnClickListener} must define the <code>onClick()</code> method, which
defines the action to be made when the checkbox is clicked. Here, we query the current state of the
checkbox, then pop up a {@link android.widget.Toast} message that displays the current state.
Notice that the CheckBox handles its own state change between checked and un-checked, so we just
ask which it currently is.</p>
<li>Run it.</li>
</ol>
<p class="note"><strong>Tip:</strong> If you find that you need to change the state
in another way (such as when loading a saved {@link android.preference.CheckBoxPreference}),
use <code>setChecked(true)</code> or <code>toggle()</code>.</p>
<h2>RadioButton</h2>
<p>Two mutually-exclusive radio buttons&mdash;enabling one disables the other.
When each is pressed, we'll pop up a message.</p>
<ol>
<li>Open the layout file and, inside the LinearLayout, add two {@link android.widget.RadioButton}s,
inside a {@link android.widget.RadioGroup}:
<pre>
&lt;RadioGroup
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
&lt;RadioButton android:id="@+id/radio_red"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Red" />
&lt;RadioButton android:id="@+id/radio_blue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Blue" />
&lt;/RadioGroup>
</pre>
</li>
<li>To do something when each is selected, we'll need an OnClickListener. Unlike the other
listeners we've created, instead of creating this one as an anonymous inner class,
we'll create it as a new object. This way, we can re-use the OnClickListener for
both RadioButtons. So, add the following code in the HelloFormStuff Activity
(<em>outside</em> the <code>onCreate()</code> method):
<pre>
OnClickListener radio_listener = new OnClickListener() {
public void onClick(View v) {
// Perform action on clicks
RadioButton rb = (RadioButton) v;
Toast.makeText(HelloFormStuff.this, rb.getText(), Toast.LENGTH_SHORT).show();
}
};
</pre>
<p>Our <code>onClick()</code> method will be handed the View clicked, so the first thing to do
is cast it into a RadioButton. Then we pop up a
{@link android.widget.Toast} message that displays the selection.</p>
<li>Now, at the bottom of the <code>onCreate()</code> method, add the following:
<pre>
final RadioButton radio_red = (RadioButton) findViewById(R.id.radio_red);
final RadioButton radio_blue = (RadioButton) findViewById(R.id.radio_blue);
radio_red.setOnClickListener(radio_listener);
radio_blue.setOnClickListener(radio_listener);
</pre>
<p>This captures each of the RadioButtons from our layout and adds the newly-created
OnClickListener to each.</p>
<li>Run it.</li>
</ol>
<p class="note"><strong>Tip:</strong> If you find that you need to change the state of a
RadioButton in another way (such as when loading a saved {@link android.preference.CheckBoxPreference}),
use <code>setChecked(true)</code> or <code>toggle()</code>.</p>
<h2>ToggleButton</h2>
<p>A button used specifically for toggling something on and off.</p>
<ol>
<li>Open the layout file and, inside the LinearLayout, add the {@link android.widget.ToggleButton} element:
<pre>
&lt;ToggleButton android:id="@+id/togglebutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</pre>
</li>
<li>To do something when the state is changed, add the following code
to the end of the <code>onCreate()</code> method:
<pre>
final ToggleButton togglebutton = (ToggleButton) findViewById(R.id.togglebutton);
togglebutton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// Perform action on clicks
if (togglebutton.isChecked()) {
Toast.makeText(HelloFormStuff.this, "ON", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(HelloFormStuff.this, "OFF", Toast.LENGTH_SHORT).show();
}
}
});
</pre>
<p>This captures our ToggleButton element from the layout, then adds an on-click listener to it.
The {@link android.view.View.OnClickListener} must define the <code>onClick()</code> method, which
defines the action to be made when the button is clicked. Here, we query the current state of the
ToggleButton, then pop up a {@link android.widget.Toast} message that displays the current state.
Notice that the ToggleButton handles its own state change between checked and un-checked, so we just
ask which it is.</p>
<li>Run it.</li>
</ol>
<p class="note"><strong>Tip:</strong> By default, the text on the button is "ON" and "OFF", but
you can change each of these with <code>setTextOn(<var>CharSequence</var>)</code> and
<code>setTextOff(<var>CharSequence</var>)</code>. And, if you find that you need to change the state
in another way (such as when loading a saved {@link android.preference.CheckBoxPreference}),
use <code>setChecked(true)</code> or <code>toggle()</code>. </p>
<p>If you've added all the form items above, your application should look something like this:</p>
<img src="images/hello-formstuff.png" width="150px" />
<h3>References</h3>
<ul>
<li>{@link android.widget.ImageButton}</li>
<li>{@link android.widget.EditText}</li>
<li>{@link android.widget.CheckBox}</li>
<li>{@link android.widget.RadioButton}</li>
<li>{@link android.widget.ToggleButton}</li>
</ul>

135
base/docs/html/guide/tutorials/views/hello-gallery.jd Normal file
View File

@ -0,0 +1,135 @@
page.title=Hello, Gallery
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.Gallery} is a View commonly used to display items in a horizontally scrolling list
that locks the current selection at the center. When one is selected, we'll show a message.</p>
<ol>
<li>Start a new project/Activity called HelloGallery.</li>
<li>Add some images to your res/drawable/ directory.</li>
<li>Open the layout file and make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;Gallery xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/gallery"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
</pre>
</li>
<li>Open the HelloGallery.java file. Insert the following for the <code>onCreate()</code> method:
<pre>
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Gallery g = (Gallery) findViewById(R.id.gallery);
g.setAdapter(new ImageAdapter(this));
g.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView parent, View v, int position, long id) {
Toast.makeText(HelloGallery.this, "" + position, Toast.LENGTH_SHORT).show();
}
});
}
</pre>
<p>We start as usual: set the layout and capture the View we want (our Gallery).
We then set an Adapter, called ImageAdapter for the Gallery&mdash;this is a new class that
we'll create next. Then we create an item click listener for the Gallery. This is like a normal
on-click listener (which you might be familiar with for buttons), but it listens to each item
that we've added to the Gallery. The <code>onItemClick()</code> callback method
receives the AdapterView where the click occurred, the specific View that received the click, the
position of the View clicked (zero-based), and the row id of the item clicked (if applicable). All
that we care about is the position, so that we can pop up a {@link android.widget.Toast} message that
tells us the index position of the item clicked. We do this with <code>Toast.makeText().show()</code>.
</p>
</li>
<li>After the <code>onCreate()</code> method, add the <code>ImageAdapter</code> class:
<pre>
public class ImageAdapter extends BaseAdapter {
int mGalleryItemBackground;
private Context mContext;
private Integer[] mImageIds = {
R.drawable.sample_1,
R.drawable.sample_2,
R.drawable.sample_3,
R.drawable.sample_4,
R.drawable.sample_5,
R.drawable.sample_6,
R.drawable.sample_7
};
public ImageAdapter(Context c) {
mContext = c;
TypedArray a = obtainStyledAttributes(android.R.styleable.Theme);
mGalleryItemBackground = a.getResourceId(
android.R.styleable.Theme_galleryItemBackground, 0);
a.recycle();
}
public int getCount() {
return mImageIds.length;
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
ImageView i = new ImageView(mContext);
i.setImageResource(mImageIds[position]);
i.setLayoutParams(new Gallery.LayoutParams(150, 100));
i.setScaleType(ImageView.ScaleType.FIT_XY);
i.setBackgroundResource(mGalleryItemBackground);
return i;
}
}
</pre>
<p>First, there are a few member variables, including an array of IDs that reference
the images we placed in our drawable resources directory.</p>
<p>Next is the constructor, where we define the member Context. The rest of the constructor
sets up a reference for our Gallery them, which adds the nice framing for each Gallery item.
Once we have our <code>mGalleryItemBackground</code>, it's important to recycle the
StyledAttribute for later re-use.</p>
<p>The next three methods are required for basic member queries.
But then we have the <code>getView()</code> method, which is called
for each item read by our ImageAdapter, when the Gallery is being built. Here, we
use our member Context to create a new {@link android.widget.ImageView}. We then define
the image resource with the current position of the Gallery items (corresponding to our
array of drawables), set the dimensions for the ImageView,
set the image scaling to fit the ImageView dimensions, then finally set the
background theme for the ImageView.</p>
<p>See {@link android.widget.ImageView.ScaleType}
for other image scaling options, in case you want to avoid stretching images that don't
exactly match the ImageView dimensions.</p>
<li>Now run it.</li>
</ol>
<p>You should see something like this:</p>
<img src="images/hello-gallery.png" width="150px" />
<h3>References</h3>
<ul>
<li>{@link android.widget.BaseAdapter}</li>
<li>{@link android.widget.Gallery}</li>
<li>{@link android.widget.ImageView}</li>
<li>{@link android.widget.Toast}</li>
</ul>

129
base/docs/html/guide/tutorials/views/hello-gridview.jd Normal file
View File

@ -0,0 +1,129 @@
page.title=Hello, GridView
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.GridView} displays items in a two-dimensional, scrolling grid. The items
are acquired from a {@link android.widget.ListAdapter}.</p>
<ol>
<li>Start a new project/Activity called HelloGridView.</li>
<li>Find some photos you'd like to use, or copy some from the SDK samples res/drawable/
folder of your project.</li>
<li>Open the layout and make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;GridView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/gridview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:numColumns="auto_fit"
android:verticalSpacing="10dp"
android:horizontalSpacing="10dp"
android:columnWidth="90dp"
android:stretchMode="columnWidth"
android:gravity="center"
/>
</pre>
</li>
<li>Open the HelloGridView Java file. Insert the following for the <code>onCreate()</code> method:
<pre>
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
GridView gridview = (GridView) findViewById(R.id.gridview);
gridview.setAdapter(new ImageAdapter(this));
}
</pre>
<p>Here, we get a handle on our GridView, from the layout, and give it an Adapter.
We're actually going to create our own Adapter called ImageAdapter.</p>
</li>
<li>Create a new class (nested or otherwise), called ImageAdapter, which extends {@link android.widget.BaseAdapter}:
<pre>
public class ImageAdapter extends BaseAdapter {
private Context mContext;
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
return mThumbIds.length;
}
public Object getItem(int position) {
return null;
}
public long getItemId(int position) {
return 0;
}
// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView;
if (convertView == null) { // if it's not recycled, initialize some attributes
imageView = new ImageView(mContext);
imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setPadding(8, 8, 8, 8);
} else {
imageView = (ImageView) convertView;
}
imageView.setImageResource(mThumbIds[position]);
return imageView;
}
// references to our images
private Integer[] mThumbIds = {
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7,
R.drawable.sample_0, R.drawable.sample_1,
R.drawable.sample_2, R.drawable.sample_3,
R.drawable.sample_4, R.drawable.sample_5,
R.drawable.sample_6, R.drawable.sample_7
};
}
</pre>
<p>First we take care of some required methods inherited from BaseAdapter.
The constructor and <code>getCount()</code> are self-explanatory. Normally, <code>getItem()</code>
should return the actual object at the specified position in our Adapter, but for this Hello World,
we're not going to bother. Likewise, <code>getItemId()</code> should return the row id of
the item, but right now we don't care.</p>
<p>However, <code>getView()</code> is the method we care about. This one creates a new View for each image that we
put in our ImageAdapter. So we're going to create an ImageView each time. When this is called, we're
going to receive a View, which is likely a recycled View object (at least after the first call), so we
check for this&mdash;if it's null, we initialize the ImageView and setup all the properties we want.
The <code>LayoutParams()</code> initialization sets the height and width of the View&mdash;this ensures
that no matter the drawable size, each image is resized and cropped to fit in the ImageView (if necessary).
With <code>setScaleType()</code>, we say that images should be cropped toward the center (if necessary).
And finally, we set the padding within the ImageView. (Note that, if the images have various aspect-ratios,
as they do in this demo, then less padding will cause for more cropping of the image, if it does not match
the dimensions given to the ImageView.) At the end of <code>getView()</code> we set the image resource and
return the ImageView.</p>
<p>All that's left is our array or drawable resources at the bottom.</p>
</li>
<li>Run it.</li>
</ol>
<p>Your grid layout should look something like this:</p>
<img src="images/hello-gridview.png" width="150px" />
<p>Try experimenting with the behaviors of the GridView and ImageView by adjusting their properties. For example,
instead of setting the ImageView LayoutParams, you can try using
{@link android.widget.ImageView#setAdjustViewBounds(boolean)}. </p>
<h3>References</h3>
<ul>
<li>{@link android.widget.GridView}</li>
<li>{@link android.widget.ImageView}</li>
<li>{@link android.widget.BaseAdapter}</li>
</ul>

130
base/docs/html/guide/tutorials/views/hello-linearlayout.jd Normal file
View File

@ -0,0 +1,130 @@
page.title=Hello, LinearLayout
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.LinearLayout} is a GroupView that will lay child View elements
vertically or horizontally.</p>
<ol>
<li>Start a new project/Activity called HelloLinearLayout.</li>
<li>Open the layout file.
Make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
&lt;LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1">
&lt;TextView
android:text="red"
android:gravity="center_horizontal"
android:background="#aa0000"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="1"/>
&lt;TextView
android:text="green"
android:gravity="center_horizontal"
android:background="#00aa00"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="1"/>
&lt;TextView
android:text="blue"
android:gravity="center_horizontal"
android:background="#0000aa"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="1"/>
&lt;TextView
android:text="yellow"
android:gravity="center_horizontal"
android:background="#aaaa00"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="1"/>
&lt;/LinearLayout>
&lt;LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1">
&lt;TextView
android:text="row one"
android:textSize="15pt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"/>
&lt;TextView
android:text="row two"
android:textSize="15pt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"/>
&lt;TextView
android:text="row three"
android:textSize="15pt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"/>
&lt;TextView
android:text="row four"
android:textSize="15pt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"/>
&lt;/LinearLayout>
&lt;/LinearLayout>
</pre>
<p>Carefully inspect the XML. You'll notice how this layout works a lot like
an HTML layout. There is one parent LinearLayout that is defined to lay
its child elements vertically. The first child is another LinearLayout that uses a horizontal layout
and the second uses a vertical layout. Each LinearLayout contains several {@link android.widget.TextView}
elements.</p>
</li>
<li>Now open the HelloLinearLayout Activity and be sure it loads this layout in the <code>onCreate()</code> method:</p>
<pre>
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
</pre>
<p><code>R.layout.main</code> refers to the <code>main.xml</code> layout file.</p>
</li>
<li>Run it.</li>
</ol>
<p>You should see the following:</p>
<img src="images/hello-linearlayout.png" width="150px" />
<p>Notice how the various XML attributes define the View's behavior.
Pay attention to the effect of the <code>layout_weight</code>. Try
experimenting with different values to see how the screen real estate is
distributed based on the weight of each element.</p>
<h3>References</h3>
<ul>
<li>{@link android.widget.LinearLayout}</li>
<li>{@link android.widget.TextView}</li>
</ul>

90
base/docs/html/guide/tutorials/views/hello-listview.jd Normal file
View File

@ -0,0 +1,90 @@
page.title=Hello, ListView
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.ListView} is a View that shows items in a vertically scrolling list. The items are
acquired from a {@link android.widget.ListAdapter}.</p>
<ol>
<li>Start a new project/ListActivity called HelloListView.</li>
<li>Open the HelloListView Java file. Make the class extend ListActivity (instead of Activity).
<pre>public class HelloListView extends ListActivity {</pre>
</li>
<li>Insert the following for the <code>onCreate()</code> method:
<pre>
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setListAdapter(new ArrayAdapter&lt;String>(this,
android.R.layout.simple_list_item_1, COUNTRIES));
getListView().setTextFilterEnabled(true);
}
</pre>
<p>Notice that we don't need to load a layout (at least, not in this case, because we're using
the whole screen for our list). Instead, we just call <code>setListAdapter()</code> (which automatically
adds a ListView to the ListActivity), and provide it with an ArrayAdapter that binds a
<code>simple_list_item_1</code> layout item to each entry in the <code>COUNTRIES</code>
array (added next). The next line of code adds a text filter to the ListView, so that when the user
begins typing, the list will filter the entire view to display only the items that match the entry.</p>
</li>
<li>Following the <code>onCreate()</code> method, add the String array:
<pre>
static final String[] COUNTRIES = new String[] {
"Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra",
"Angola", "Anguilla", "Antarctica", "Antigua and Barbuda", "Argentina",
"Armenia", "Aruba", "Australia", "Austria", "Azerbaijan",
"Bahrain", "Bangladesh", "Barbados", "Belarus", "Belgium",
"Belize", "Benin", "Bermuda", "Bhutan", "Bolivia",
"Bosnia and Herzegovina", "Botswana", "Bouvet Island", "Brazil", "British Indian Ocean Territory",
"British Virgin Islands", "Brunei", "Bulgaria", "Burkina Faso", "Burundi",
"Cote d'Ivoire", "Cambodia", "Cameroon", "Canada", "Cape Verde",
"Cayman Islands", "Central African Republic", "Chad", "Chile", "China",
"Christmas Island", "Cocos (Keeling) Islands", "Colombia", "Comoros", "Congo",
"Cook Islands", "Costa Rica", "Croatia", "Cuba", "Cyprus", "Czech Republic",
"Democratic Republic of the Congo", "Denmark", "Djibouti", "Dominica", "Dominican Republic",
"East Timor", "Ecuador", "Egypt", "El Salvador", "Equatorial Guinea", "Eritrea",
"Estonia", "Ethiopia", "Faeroe Islands", "Falkland Islands", "Fiji", "Finland",
"Former Yugoslav Republic of Macedonia", "France", "French Guiana", "French Polynesia",
"French Southern Territories", "Gabon", "Georgia", "Germany", "Ghana", "Gibraltar",
"Greece", "Greenland", "Grenada", "Guadeloupe", "Guam", "Guatemala", "Guinea", "Guinea-Bissau",
"Guyana", "Haiti", "Heard Island and McDonald Islands", "Honduras", "Hong Kong", "Hungary",
"Iceland", "India", "Indonesia", "Iran", "Iraq", "Ireland", "Israel", "Italy", "Jamaica",
"Japan", "Jordan", "Kazakhstan", "Kenya", "Kiribati", "Kuwait", "Kyrgyzstan", "Laos",
"Latvia", "Lebanon", "Lesotho", "Liberia", "Libya", "Liechtenstein", "Lithuania", "Luxembourg",
"Macau", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali", "Malta", "Marshall Islands",
"Martinique", "Mauritania", "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova",
"Monaco", "Mongolia", "Montserrat", "Morocco", "Mozambique", "Myanmar", "Namibia",
"Nauru", "Nepal", "Netherlands", "Netherlands Antilles", "New Caledonia", "New Zealand",
"Nicaragua", "Niger", "Nigeria", "Niue", "Norfolk Island", "North Korea", "Northern Marianas",
"Norway", "Oman", "Pakistan", "Palau", "Panama", "Papua New Guinea", "Paraguay", "Peru",
"Philippines", "Pitcairn Islands", "Poland", "Portugal", "Puerto Rico", "Qatar",
"Reunion", "Romania", "Russia", "Rwanda", "Sqo Tome and Principe", "Saint Helena",
"Saint Kitts and Nevis", "Saint Lucia", "Saint Pierre and Miquelon",
"Saint Vincent and the Grenadines", "Samoa", "San Marino", "Saudi Arabia", "Senegal",
"Seychelles", "Sierra Leone", "Singapore", "Slovakia", "Slovenia", "Solomon Islands",
"Somalia", "South Africa", "South Georgia and the South Sandwich Islands", "South Korea",
"Spain", "Sri Lanka", "Sudan", "Suriname", "Svalbard and Jan Mayen", "Swaziland", "Sweden",
"Switzerland", "Syria", "Taiwan", "Tajikistan", "Tanzania", "Thailand", "The Bahamas",
"The Gambia", "Togo", "Tokelau", "Tonga", "Trinidad and Tobago", "Tunisia", "Turkey",
"Turkmenistan", "Turks and Caicos Islands", "Tuvalu", "Virgin Islands", "Uganda",
"Ukraine", "United Arab Emirates", "United Kingdom",
"United States", "United States Minor Outlying Islands", "Uruguay", "Uzbekistan",
"Vanuatu", "Vatican City", "Venezuela", "Vietnam", "Wallis and Futuna", "Western Sahara",
"Yemen", "Yugoslavia", "Zambia", "Zimbabwe"
};
</pre>
</li>
<li> Run it.</li>
</ol>
<p>You can scroll the list, or type to filter it. You should see something like this:</p>
<img src="images/hello-listview.png" width="150px" />
<h3>References</h3>
<ul>
<li>{@link android.widget.ListView}</li>
<li>{@link android.widget.ListAdapter}</li>
</ul>

245
base/docs/html/guide/tutorials/views/hello-mapview.jd Normal file
View File

@ -0,0 +1,245 @@
page.title=Hello, MapView
parent.title=Hello, Views
parent.link=index.html
@jd:body
<div class="special">
<p>This tutorial requires that you have the Google Maps external library
installed in your SDK environment. By default the Android SDK includes the
Google APIs add-on, which in turn includes the Maps external library. If you
don't have the Google APIs SDK add-on, you can download it from this
location:</p>
<p style="margin-left:2em;"><a
href="http://code.google.com/android/add-ons/google-apis">http://code.google.com/android/add-ons/google-apis</a></p>
<p>The Google APIs add-on requires Android 1.5 SDK or later release. After
installing the add-on in your SDK, set your project properties to use the build
target called "Google APIs Add-on". See the instructions for setting a build
target in <a href="{@docRoot}guide/developing/eclipse-adt.html">Developing in
Eclipse with ADT</a> or <a
href="{@docRoot}guide/developing/other-ide.html">Developing in Other IDEs</a>,
as appropriate for your environment. </p>
<p>You will also need to use the android tool to set up an AVD that uses the
Google APIs deployment target. See <a
href="{@docRoot}guide/developing/tools/avd.html">Android Virtual Devices</a> for
more information. Once you have set up your environment, you will be able to
build and run the project described in this tutorial</a></p>
</div>
<p>A MapView allows you to create your own map-viewing Activity.
First, we'll create a simple Activity that can view and navigate a map. Then we will add some overlay items.</p>
<ol>
<li>Start a new project/Activity called HelloMapView.
<li>Because we're using the Google Maps library,
which is not a part of the standard Android library, we need to
declare it in the Android Manifest. Open the AndroidManifest.xml
file and add the following as a child of the <code>&lt;application></code> element:
<pre>&lt;uses-library android:name="com.google.android.maps" /></pre>
</li>
<li>We also need access to the internet in order to retrieve the Google Maps tiles,
so the application must request the {@link android.Manifest.permission#INTERNET INTERNET} permissions.
In the manifest file, add the following as a child of the <code>&lt;manifest></code> element:
<pre>&lt;uses-permission android:name="android.permission.INTERNET" /></pre>
</li>
<li>Now open the main layout file for your project. Define a layout with a com.google.android.maps.MapView
inside a android.widget.RelativeLayout:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/mainlayout"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
&lt;com.google.android.maps.MapView
android:id="@+id/mapview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
android:apiKey="<em>Your Maps API Key</em>"
/>
&lt;/RelativeLayout>
</pre>
<p>The <code>clickable</code> attribute defines whether you want to allow user-interaction with the map.
In this case, we set it "true" so that the user can navigate.</p>
<p>The <code>apiKey</code> attribute holds the Google Maps API Key that proves your application and signer
certificate has been registered with the Google Maps service. Because MapView uses Google Maps data, this key is required
in order to receive the map data, even while you are developing. Registration is free and it only takes a couple
minutes to register your certificate and receive a Maps API Key. For instructions on getting a key, read
<a href="http://code.google.com/android/add-ons/google-apis/mapkey.html">Obtaining a Maps API Key</a>.
(For the purpose of this tutorial, you should register with the fingerprint of the SDK debug certificate.)
Once you've acquired the Maps API Key, insert it for the <code>apiKey</code> value.</p></li>
<li>Now open the HelloMapView.java file. For this Activity, we're going to extend the special sub-class of
Activity called MapActivity, so change the class declaration to extend
MapActivity, instead of Activity:</p>
<pre>public class HelloMapView extends MapActivity {</pre>
<li>The <code>isRouteDisplayed()</code> method is required, so add it inside the class:
<pre>
&#64;Override
protected boolean isRouteDisplayed() {
return false;
}
</pre>
<p>You can actually run this now, but all it does is allow you to pan around the map.</p>
<li>Now go back to the HelloMapView class. We'll now retrieve the ZoomControls object from
the MapView and add it to our new layout element. First, at the top of the HelloMapView,
instantiate handles for the MapView and LinearLayout, plus a ZoomControl object:
<pre>
LinearLayout linearLayout;
MapView mapView;
</pre>
<li>Then initialize each of these in <code>onCreate()</code>. We'll capture the LinearLayout and
MapView through their layout resources. Then get the ZoomControls from the MapView::
<pre>
mapView = (MapView) findViewById(R.id.mapview);
mapView.setBuiltInZoomControls(true);
</pre>
<p>By using the built-in zoom control provided by MapView, we don't have to do any of the work
required to actually perform the zoom operations. The controls will appear whenever the user
touches the map, then disappear after a few moments of inactivity.</p></li>
<li>Run it.</li>
</ol>
<hr/>
<p>So, we now have full interaction controls. All well and good, but what we really want our map
for is custom markers and layovers. Let's add some Overlay
objects to our map. To do this, we're going to
implement the ItemizedOverlay
class, which can manage a whole set of Overlay items for us.</p>
<ol>
<li>Create a new Java class named HelloItemizedOverlay that implements ItemizedOverlay.
<p>When using Eclipse, right-click the package name in the Eclipse Package Explorer, and select New > Class. Fill-in
the Name field as <em>HelloItemizedOverlay</em>. For the Superclass, enter
<em>com.google.android.maps.ItemizedOverlay</em>. Click the checkbox for <em>Constructors from
superclass</em>. Click Finish.</p></li>
<li> First thing, we need an OverlayItem ArrayList, in which we'll put each of the OverlayItem
objects we want on our map. Add this at the top of the HelloItemizedOverlay class:
<pre>private ArrayList&lt;OverlayItem> mOverlays = new ArrayList&lt;OverlayItem>();</pre></li>
<li>All the constructor does is define the default marker to be used on each of the OverlayItems.
In order for the Drawable to actually get drawn, it must have its bounds defined. And we want the
center-point at the bottom of the image to be the point at which it's attached to the map
coordinates. We handle all this with the boundCenterBottom() method. Wrap this around our
defaultMarker, so the super constructor call looks like this:
<pre>super(boundCenterBottom(defaultMarker));</pre></li>
<li>In order to add new OverlayItems to our ArrayList, we need a new public method. We'll handle
this with the following method:
<pre>
public void addOverlay(OverlayItem overlay) {
mOverlays.add(overlay);
populate();
}</pre>
<p>Each time we add a new OverlayItem, we must call <code>populate()</code>, which will read each of out
OverlayItems and prepare them to be drawn.</p></li>
<li>In order for the <code>populate()</code> method to read each OverlayItem, it will make a request to
<code>createItem(int)</code>. We must define this method to properly read from our ArrayList. Replace the
existing contents of the createItem method with a <code>get()</code> call to our ArrayList:
<pre>
&#64;Override
protected OverlayItem createItem(int i) {
return mOverlays.get(i);
}
</pre></li>
<li>We're also required to override the <code>size()</code> method. Replace the existing contents of the
method with a size request to our ArrayList:
<pre>return mOverlays.size();</pre></li>
</ol>
<p>That's it for the HelloItemizedOverlay class. We're now ready to use it.</p>
<hr/>
<p>Go back to the HelloMapView
class. We'll start by creating one OverlayItem, adding to an instance of our HelloItemizedOverlay,
and then adding this to the MapView.</p>
<img src="images/androidmarker.png" align="right" />
<p>First, we need the image that we'll use for our map overlay. Here, we'll use the Android on the
right as our marker. Drag this image (or your own) to the res/drawable/ directory of your project workspace.</p>
<p>Now we're ready to work in the HelloMapView:</p>
<ol>
<li>First we need some more types. Add the following at the top of the HelloMapView class:
<pre>
List&lt;Overlay> mapOverlays;
Drawable drawable;
HelloItemizedOverlay itemizedOverlay;</pre></li>
<li>Now pick up where we left off in the <code>onCreate()</code> method. Instantiate the
new fields:
<pre>
mapOverlays = mapView.getOverlays();
drawable = this.getResources().getDrawable(R.drawable.androidmarker);
itemizedoverlay = new HelloItemizedOverlay(drawable);</pre>
<p>All overlay elements on a map are held by the MapView, so when we want to add some, we must
first retrieve the List with <code>getOverlays()</code> methods. We instantiate the Drawable, which will
be used as our map marker, by using our Context resources to get the Drawable we placed in
the res/drawable/ directory (androidmarker.png). Our HelloItemizedOverlay takes the Drawable in order to set the
default marker.</p></li>
<li>Now let's make our first OverlayItem by creating a GeoPoint
that defines our map coordinates, then pass it to a new OverlayItem:
<pre>
GeoPoint point = new GeoPoint(19240000,-99120000);
OverlayItem overlayitem = new OverlayItem(point, "", "");</pre>
<p>GeoPoint coordinates are based in microdegrees (degrees * 1e6). The OverlayItem takes this
GeoPoint and two strings. Here, we won't concern ourselves with the strings, which can display
text when we click our marker, because we haven't yet written the click handler for the OverlayItem.</p></li>
<li>All that's left is for us to add this OverlayItem to our collection in the HelloItemizedOverlay,
and add this to the List of Overlay objects retrieved from the MapView:
<pre>
itemizedoverlay.addOverlay(overlayitem);
mapOverlays.add(itemizedoverlay);</pre></li>
<li>Run it!</li>
</ol>
<p>We've sent our droid to Mexico City. Hola, Mundo!</p>
<p>You should see the following:</p>
<img src="images/hello-mapview.png" width="150px" />
<p>Because we created our ItemizedOverlay class with an ArrayList, we can continue adding new
OverlayItems. Try adding another one. Before the <code>addOverlay()</code> method is called, add these lines:</p>
<pre>
GeoPoint point2 = new GeoPoint(35410000, 139460000);
OverlayItem overlayitem2 = new OverlayItem(point2, "", "");
</pre>
<p>Run it again... We've sent a new droid to Tokyo. Sekai, konichiwa!</p>

75
base/docs/html/guide/tutorials/views/hello-relativelayout.jd Normal file
View File

@ -0,0 +1,75 @@
page.title=Hello, RelativeLayout
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.RelativeLayout} is a ViewGroup that allows you to layout child elements
in positions relative to the parent or siblings elements.</p>
<ol>
<li>Start a new project/Activity called HelloRelativeLayout.</li>
<li>Open the layout file. Make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
&lt;TextView
android:id="@+id/label"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Type here:"/>
&lt;EditText
android:id="@+id/entry"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@android:drawable/editbox_background"
android:layout_below="@id/label"/>
&lt;Button
android:id="@+id/ok"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/entry"
android:layout_alignParentRight="true"
android:layout_marginLeft="10dip"
android:text="OK" />
&lt;Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="@id/ok"
android:layout_alignTop="@id/ok"
android:text="Cancel" />
&lt;/RelativeLayout>
</pre>
<p>Pay attention to each of the additional <code>layout_*</code> attributes (besides the
usual width and height, which are required for all elements). When using relative layout,
we use attributes like <code>layout_below</code> and <code>layout_toLeftOf</code> to describe
how we'd like to position each View. Naturally, these are different relative positions, and the
value of the attribute is the id of the element we want the position relative to.</p>
</li>
<li>Make sure your Activity loads this layout in the <code>onCreate()</code> method:</p>
<pre>
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
</pre>
<p><code>R.layout.main</code> refers to the <code>main.xml</code> layout file.</p>
</li>
<li>Run it.</li>
</ol>
<p>You should see the following:</p>
<img src="images/hello-relativelayout.png" width="150px" />
<h3>Resources</h3>
<ul>
<li>{@link android.widget.RelativeLayout}</li>
<li>{@link android.widget.TextView}</li>
<li>{@link android.widget.EditText}</li>
<li>{@link android.widget.Button}</li>
</ul>

106
base/docs/html/guide/tutorials/views/hello-spinner.jd Normal file
View File

@ -0,0 +1,106 @@
page.title=Hello, Spinner
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.Spinner} is a widget that allows the user to select an item from a group.
It is similar to a dropdown list and will allow scrolling when the
list exceeds the available vertical space on the screen.</p>
<ol>
<li>Start a new project/Activity called HelloSpinner.</li>
<li>Open the layout file.
Make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:padding="10dip"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
&lt;TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dip"
android:text="Please select a planet:"
/>
&lt;Spinner
android:id="@+id/spinner"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:drawSelectorOnTop="true"
android:prompt="@string/planet_prompt"
/>
&lt;/LinearLayout>
</pre>
<p>Notice that the Spinner's <code>android:prompt</code> is a string resource. In
this case, Android does not allow it to be a string, it must be a reference to a resource.
So...</p>
</li>
<li>Open the strings.xml file in res/values/ and add the following <code>&lt;string></code>
element inside the <code>&lt;resources></code> element:
<pre>
&lt;string name="planet_prompt">Choose a planet&lt;/string>
</pre>
</li>
<li>Create a new XML file in res/values/ called arrays.xml. Insert the following:
<pre>
&lt;resources>
&lt;string-array name="planets">
&lt;item>Mercury&lt;/item>
&lt;item>Venus&lt;/item>
&lt;item>Earth&lt;/item>
&lt;item>Mars&lt;/item>
&lt;item>Jupiter&lt;/item>
&lt;item>Saturn&lt;/item>
&lt;item>Uranus&lt;/item>
&lt;item>Neptune&lt;/item>
&lt;/string-array>
&lt;/resources>
</pre>
<p>This is the list of items (planets) that the user can select from in the Spinner widget.</p>
</li>
<li>Now open the HelloSpinner.java file. Insert the following code into the HelloSpinner class:
<pre>
&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Spinner s = (Spinner) findViewById(R.id.spinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.planets, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
s.setAdapter(adapter);
}
</pre>
<p>That's it. We start by creating a Spinner from our layout. We then create an {@link android.widget.ArrayAdapter}
that binds each element of our string array to a layout view&mdash;we pass <code>createFromResource</code> our Context,
the array of selectable items and the type of layout we'd like each one bound to. We then call
<code>setDropDownViewResource()</code> to define the type of layout in which to present the
entire collection. Finally, we set this Adapter to associate with our Spinner,
so the string items have a place to go.</p>
</li>
<li>Now run it.</li>
</ol>
<p>It should look like this:</p>
<img src="images/hello-spinner.png" width="150px" />
<h3>Resources</h3>
<ul>
<li>{@link android.R.layout}</li>
<li>{@link android.widget.ArrayAdapter}</li>
<li>{@link android.widget.Spinner}</li>
</ul>

118
base/docs/html/guide/tutorials/views/hello-tablelayout.jd Normal file
View File

@ -0,0 +1,118 @@
page.title=Hello, TableLayout
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.TableLayout} is a ViewGroup that
will lay child View elements into rows and columns.</p>
<ol>
<li>Start a new project/Activity called HelloTableLayout.</li>
<li>Open the layout file.
Make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:stretchColumns="1">
&lt;TableRow>
&lt;TextView
android:layout_column="1"
android:text="Open..."
android:padding="3dip" />
&lt;TextView
android:text="Ctrl-O"
android:gravity="right"
android:padding="3dip" />
&lt;/TableRow>
&lt;TableRow>
&lt;TextView
android:layout_column="1"
android:text="Save..."
android:padding="3dip" />
&lt;TextView
android:text="Ctrl-S"
android:gravity="right"
android:padding="3dip" />
&lt;/TableRow>
&lt;TableRow>
&lt;TextView
android:layout_column="1"
android:text="Save As..."
android:padding="3dip" />
&lt;TextView
android:text="Ctrl-Shift-S"
android:gravity="right"
android:padding="3dip" />
&lt;/TableRow>
&lt;View
android:layout_height="2dip"
android:background="#FF909090" />
&lt;TableRow>
&lt;TextView
android:text="X"
android:padding="3dip" />
&lt;TextView
android:text="Import..."
android:padding="3dip" />
&lt;/TableRow>
&lt;TableRow>
&lt;TextView
android:text="X"
android:padding="3dip" />
&lt;TextView
android:text="Export..."
android:padding="3dip" />
&lt;TextView
android:text="Ctrl-E"
android:gravity="right"
android:padding="3dip" />
&lt;/TableRow>
&lt;View
android:layout_height="2dip"
android:background="#FF909090" />
&lt;TableRow>
&lt;TextView
android:layout_column="1"
android:text="Quit"
android:padding="3dip" />
&lt;/TableRow>
&lt;/TableLayout>
</pre>
<p>Notice how this resembles the structure of an HTML table. <code>TableLayout</code> is like the
<code>table</code> element; <code>TableRow</code> is like a <code>tr</code> element; but for our cells like
the html <code>td</code> element, we can use any kind of View. Here, we use <code>TextView</code> for the cells.</p>
</li>
<li>Make sure your Activity loads this layout in the <code>onCreate()</code> method:
<pre>
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
</pre>
<p><code>R.layout.main</code> refers to the <code>main.xml</code> layout file.</p>
</li>
<li>Run it.</li>
</ol>
<p>You should see the following:</p>
<img src="images/hello-tablelayout.png" width="150px" />
<h3>References</h3>
<ul>
<li>{@link android.widget.TableLayout}</li>
<li>{@link android.widget.TableRow}</li>
<li>{@link android.widget.TextView}</li>
</ul>

124
base/docs/html/guide/tutorials/views/hello-tabwidget.jd Normal file
View File

@ -0,0 +1,124 @@
page.title=Hello, TabWidget
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.TabWidget} offers the ability to easily draw an interface that uses
tabs to navigate between different views.</p>
<ol>
<li>Start a new project/Activity called HelloTabWidget.</li>
<li>Open the layout file and make it like so:</li>
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
&lt;LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
&lt;TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
&lt;FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
&lt;TextView
android:id="@+id/textview1"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="this is a tab" />
&lt;TextView
android:id="@+id/textview2"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="this is another tab" />
&lt;TextView
android:id="@+id/textview3"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="this is a third tab" />
&lt;/FrameLayout>
&lt;/LinearLayout>
&lt;/TabHost>
</pre>
<p>Here, we've created a {@link android.widget.TabHost} that contains the entire layout of the Activity.
A TabHost requires two descendant elements: a {@link android.widget.TabWidget} and a {@link android.widget.FrameLayout}.
In order to properly layout these elements, we've put them inside a vertical {@link android.widget.LinearLayout}.
The FrameLayout is where we keep the content that will change with each tab. Each child in the FrameLayout will
be associated with a different tab.
In this case, each tab simply shows a different {@link android.widget.TextView} with some text. </p>
<p>Notice that the TabWidget and the FrameLayout elements have specific <code>android</code> namespace IDs. These are necessary
so that the TabHost can automatically retrieve references to them, populate the TabWidget with the tabs that we'll define
in our code, and swap the views in the FrameLayout. We've also defined our own IDs for each TextView, which we'll use to
associate each tab with the view that it should reveal.</p>
<p>Of course, you can
make these child views as large as complex as you'd like &mdash; instead of the TextView elements,
you could start with other layout views and build a unique layout hierarchy for each tab.</p>
</li>
<li>Now we'll add our code. Open HelloTabWidget.java and make it a <code>TabActivity</code>.
<p>By default, Eclipse creates a class that extends <code>Activity</code>. Change it to
extend <code>TabActivity</code>:</p>
<pre>
public class HelloTabWidget extends TabActivity {
</pre>
</li>
<li>Now fill in the the <code>onCreate</code> method like this:
<pre>
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mTabHost = getTabHost();
mTabHost.addTab(mTabHost.newTabSpec("tab_test1").setIndicator("TAB 1").setContent(R.id.textview1));
mTabHost.addTab(mTabHost.newTabSpec("tab_test2").setIndicator("TAB 2").setContent(R.id.textview2));
mTabHost.addTab(mTabHost.newTabSpec("tab_test3").setIndicator("TAB 3").setContent(R.id.textview3));
mTabHost.setCurrentTab(0);
}
</pre>
<p>As usual, we start by setting our layout.</p>
<p>We then call the TabActivity method <code>getTabHost()</code>,
which returns us a reference to the TabHost we created in our layout. Upon our TabHost, we call <code>addTab()</code>
for each of the tabs that we want to add to the TabWidget. Each time we call this, we pass a
{@link android.widget.TabHost.TabSpec} that we build on the fly, and with it, chain together two necessary methods:
<code>setIndicator()</code> to set the text for the tab button, and <code>setContent()</code> to define
which View we want to associate with the tab and reveal when pressed. Our indicator is just a text string and
our content is an ID reference to the TextView elements we inserted in the FrameLayout.</p>
<p>At the end, we call <code>setCurrentTab()</code> to define which tab should be opened by default. The tabs
are saved like a zero-based array, so to open the first tab, we pass zero (<var>0</var>).</p>
</li>
<li>To clean-up the presentation a bit more, let's remove the window title that appears at the top of the layout.
Android includes a theme that removes that title for us. To add it, open the Android Manifest file and add
the <var>NoTitleBar</var> theme to the <code>&lt;application></code> tag. It should end up like this:
<pre>
&lt;application android:icon="&#64;drawable/icon" android:theme="&#64;android:style/Theme.NoTitleBar">
</pre>
</li>
<li>That's it. Run your application.</li>
</ol>
<p>Your application should look like this:</p>
<img src="images/hello-tabwidget.png" width="150px" />
<div class="special"><p>You can include icons in your tabs by passing a
{@link android.graphics.drawable.Drawable} when you call <code>setIndicator()</code>. Here's an example
that uses a Drawable created from an image in the project resources:</p>
<pre>setIndicator("TAB 1", getResources().getDrawable(R.drawable.tab_icon))</pre>
</div>
<h3>References</h3>
<ul>
<li>{@link android.widget.TabWidget}</li>
<li>{@link android.widget.TabHost}</li>
<li>{@link android.widget.TabHost.TabSpec}</li>
<li>{@link android.widget.FrameLayout}</li>
</ul>

159
base/docs/html/guide/tutorials/views/hello-timepicker.jd Normal file
View File

@ -0,0 +1,159 @@
page.title=Hello, TimePicker
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.widget.TimePicker} is a widget that allows the
user to select the time by hour, minute and AM or PM.</p>
<ol>
<li>Start a new project/Activity called HelloTimePicker.</li>
<li>Open the layout file and make it like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
&lt;TextView android:id="@+id/timeDisplay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""/>
&lt;Button android:id="@+id/pickTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Change the time"/>
&lt;/LinearLayout>
</pre>
<p>For the layout, we're using a vertical LinearLayout, with a {@link android.widget.TextView} that
will display the time and a {@link android.widget.Button} that will initiate the
{@link android.widget.TimePicker} dialog.
With this layout, the TextView will sit above the Button.
The text value in the TextView is set empty, as it will be filled by our Activity
with the current time.</p>
</li>
<li>Open HelloTimePicker.java. Insert the following to the HelloTimePicker class:
<pre>
private TextView mTimeDisplay;
private Button mPickTime;
private int mHour;
private int mMinute;
static final int TIME_DIALOG_ID = 0;
&#64;Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// capture our View elements
mTimeDisplay = (TextView) findViewById(R.id.timeDisplay);
mPickTime = (Button) findViewById(R.id.pickTime);
// add a click listener to the button
mPickTime.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
showDialog(TIME_DIALOG_ID);
}
});
// get the current time
final Calendar c = Calendar.getInstance();
mHour = c.get(Calendar.HOUR_OF_DAY);
mMinute = c.get(Calendar.MINUTE);
// display the current date
updateDisplay();
}
</pre>
<p class="note"><strong>Tip:</strong> Press Ctrl(or Cmd) + Shift + O to import all needed packages.</p>
<p>We start by instantiating variables for our View elements and time fields.
The <code>TIME_DIALOG_ID</code> is a static integer that uniquely identifies the dialog. In the
<code>onCreate()</code> method, we get prepared by setting the layout and capturing the View elements.
We then set an on-click listener for the Button, so that when it is clicked, it will
show our TimePicker dialog. The <code>showDialog()</code> method will perform a callback
to our Activity. (We'll define this callback in the next section.) We then create an
instance of {@link java.util.Calendar} and get the current hour and minute. Finally, we call
<code>updateDisplay()</code>&mdash;our own method that will fill the TextView with the time.</p>
</li>
<li>After the <code>onCreate()</code> method, add the <code>onCreateDialog()</code> callback method:
<pre>
&#64;Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case TIME_DIALOG_ID:
return new TimePickerDialog(this,
mTimeSetListener, mHour, mMinute, false);
}
return null;
}
</pre>
<p>This is passed the identifier we gave <code>showDialog()</code> and initializes
the TimePicker to the time we retrieved from our Calendar instance. It will be called by
<code>showDialog()</code>.</p>
</li>
<li>Now add our <code>updateDisplay()</code> method:
<pre>
// updates the time we display in the TextView
private void updateDisplay() {
mTimeDisplay.setText(
new StringBuilder()
.append(pad(mHour)).append(":")
.append(pad(mMinute)));
}
</pre>
<p>This simply takes our member fields for the time and inserts them in
the <code>mTimeDisplay</code> TextView. Note that we call a new method, <code>pad()</code>,
on the hour and minute. (We'll create this method in the last step.)</p>
</li>
<li>Next, add a listener to be called when the time is reset:
<pre>
// the callback received when the user "sets" the time in the dialog
private TimePickerDialog.OnTimeSetListener mTimeSetListener =
new TimePickerDialog.OnTimeSetListener() {
public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
mHour = hourOfDay;
mMinute = minute;
updateDisplay();
}
};
</pre>
<p>Now when the user is done setting the time (clicks the "Set" button), we update our member fields with
the new time and update our TextView.</p>
</li>
<li>Finally, add the <code>pad()</code> method that we called from the <code>updateDisplay()</code>:
<pre>
private static String pad(int c) {
if (c >= 10)
return String.valueOf(c);
else
return "0" + String.valueOf(c);
}
</pre>
<p>This method returns the appropriate String representation of the hour or minute.
It will prefix a zero to the number if it's a single digit.
</p>
</li>
<li>Now run it.</li>
</ol>
<p>When you press the "Change the time" button, you should see the following:</p>
<img src="images/hello-timepicker.png" width="150px" />
<h3>References</h3>
<ol>
<li>{@link android.widget.TimePicker}</li>
<li>{@link android.widget.Button}</li>
<li>{@link android.widget.TextView}</li>
<li>{@link java.util.Calendar}</li>
</ol>

118
base/docs/html/guide/tutorials/views/hello-webview.jd Normal file
View File

@ -0,0 +1,118 @@
page.title=Hello, WebView
parent.title=Hello, Views
parent.link=index.html
@jd:body
<p>A {@link android.webkit.WebView} allows you to create your own web browser Activity. In this tutorial,
we'll create a simple Activity that can view web pages.</p>
<ol>
<li>Create a new project/Activity called HelloWebView.</li>
<li>Open the layout file. Insert a WebView so it looks like so:
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
&lt;WebView
android:id="@+id/webview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
/>
&lt;/LinearLayout>
</pre></li>
<li>Now open the HelloWebView.java file.
At the top of the class, instantiate a WebView object:
<pre>WebView webview;</pre>
<p> Then add the following at the end of the <code>onCreate()</code> method:</p>
<pre>
webview = (WebView) findViewById(R.id.webview);
webview.getSettings().setJavaScriptEnabled(true);
webview.loadUrl("http://www.google.com");
</pre>
<p>This captures the WebView we created in our layout, then requests a
{@link android.webkit.WebSettings} object and enables JavaScript.
Then we load a URL.</p></li>
<li>Because we're accessing the internet, we need to add the appropriate
permissions to the Android manifest file. So open the AndroidManifest.xml file
and, add the following as a child of the <code>&lt;manifest></code> element:
<pre>&lt;uses-permission android:name="android.permission.INTERNET" /></pre></li>
<li>Now run it.</li>
</ol>
<p> You now have the world's simplest web page viewer.
It's not quite a browser yet. It only loads the page we've requested.</p>
<hr/>
<p>We can load a page, but as soon as we click a link, the default Android web browser
handles the Intent, instead of our own WebView handling the action. So now we'll
override the {@link android.webkit.WebViewClient} to enable us to handle our own URL loading.</p>
<ol>
<li>In the HelloAndroid Activity, add this nested private class:
<pre>
private class HelloWebViewClient extends WebViewClient {
&#64;Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return true;
}
}</pre></li>
<li>Now, in the <code>onCreate()</code> method, set an instance of the <code>HelloWebViewClient</code>
as our WebViewClient:
<pre>webview.setWebViewClient(new WebViewClientDemo());</pre>
<p>This line should immediately follow the initialization of our WebView object.</p>
<p>What we've done is create a WebViewClient that will load any URL selected in our
WebView in the same WebView. You can see this in the <code>shouldOverrideUrlLoading()</code>
method, above&mdash;it is passed the current WebView and the URL, so all we do
is load the URL in the given view. Returning <var>true</var> says that we've handled the URL
ourselves and the event should not bubble-up.</p>
<p>If you try it again, new pages will now load in the HelloWebView Activity. However, you'll notice that
we can't navigate back. We need to handle the back button
on the device, so that it will return to the previous page, rather than exit the application.</p>
</li>
<li>To handle the back button key press, add the following method inside the HelloWebView
Activity:
<pre>
&#64;Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && webview.canGoBack()) {
webview.goBack();
return true;
}
return super.onKeyDown(keyCode, event);
}</pre>
<p>The condition uses a {@link android.view.KeyEvent} to check
whether the key pressed is the BACK button and whether the
WebView is actually capable of navigating back (if it has a history). If both are
<em>not</em> true, then we send the event up the chain (and the Activity will close).
But if both <em>are</em> true, then we call <code>goBack()</code>,
which will navigate back one step in the history. We then return true to indicate
that we've handled the event.</p>
</li>
</ol>
<p>When you open the application, it should look like this:</p>
<img src="images/hello-webview.png" width="150px" />
<h3>Resource</h3>
<ul>
<li>{@link android.webkit.WebView}</li>
<li>{@link android.webkit.WebViewClient}</li>
<li>{@link android.view.KeyEvent}</li>
</ul>

BIN
base/docs/html/guide/tutorials/views/images/android.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 693 B

BIN
base/docs/html/guide/tutorials/views/images/androidmarker.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 702 B

BIN
base/docs/html/guide/tutorials/views/images/hello-autocomplete.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 4.5 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-datepicker.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 7.2 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-formstuff.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 4.2 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-gallery.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 5.5 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-gridview.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 21 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-linearlayout.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 4.1 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-listview.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 6.8 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-mapview.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 16 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-relativelayout.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 2.3 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-spinner.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 2.5 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-tablelayout.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 3.4 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-tabwidget.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 2.1 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-timepicker.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 5.5 KiB

BIN
base/docs/html/guide/tutorials/views/images/hello-webview.png Executable file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 5.7 KiB

118
base/docs/html/guide/tutorials/views/index.jd Normal file
View File

@ -0,0 +1,118 @@
page.title=Hello, Views
@jd:body
<style>
.view {float:left; margin:10px; font-size:120%; font-weight:bold;}
.view img {border:1px solid black; margin:5px 0 0; padding:5px;}
</style>
<p>This collection of "Hello World"-style tutorials is designed
to get you quickly started with common Android Views and widgets. The aim is to let you copy and paste
these kinds of boring bits so you can focus on developing the code that makes your Android application rock.
Of course, we'll discuss some of the given code so that it all makes sense.</p>
<p>Note that a certain amount of knowledge is assumed for these tutorials. If you haven't
completed the <a href="{@docRoot}resources/tutorials/hello-world.html">Hello, World</a> tutorial,
please do so&mdash;it will teach you many things you should know about basic
Android development and Eclipse features. More specifically, you should know:</p>
<ul>
<li>How to create a new Android project.</li>
<li>The basic structure of an Android project (resource files, layout files, etc.).</li>
<li>The essential components of an {@link android.app.Activity}.</li>
<li>How to build and run a project.</li>
</ul>
<p>Please, also notice that, in order to make these tutorials simple, some may
not convey the better Android coding practices. In particular, many of them
use hard-coded strings in the layout files&mdash;the better practice is to reference strings from
your strings.xml file.</p>
<p>With this knowledge, you're ready to begin, so take your pick.</p>
<div>
<div class="view">
<a href="hello-linearlayout.html">LinearLayout</a><br/>
<a href="hello-linearlayout.html"><img src="images/hello-linearlayout.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-relativelayout.html">RelativeLayout</a><br/>
<a href="hello-relativelayout.html"><img src="images/hello-relativelayout.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-tablelayout.html">TableLayout</a><br/>
<a href="hello-tablelayout.html"><img src="images/hello-tablelayout.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-datepicker.html">DatePicker</a><br/>
<a href="hello-datepicker.html"><img src="images/hello-datepicker.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-timepicker.html">TimePicker</a><br/>
<a href="hello-timepicker.html"><img src="images/hello-timepicker.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-formstuff.html">Form Stuff</a><br/>
<a href="hello-formstuff.html"><img src="images/hello-formstuff.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-spinner.html">Spinner</a><br/>
<a href="hello-spinner.html"><img src="images/hello-spinner.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-autocomplete.html">AutoComplete</a><br/>
<a href="hello-autocomplete.html"><img src="images/hello-autocomplete.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-listview.html">ListView</a><br/>
<a href="hello-listview.html"><img src="images/hello-listview.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-gridview.html">GridView</a><br/>
<a href="hello-gridview.html"><img src="images/hello-gridview.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-gallery.html">Gallery</a><br/>
<a href="hello-gallery.html"><img src="images/hello-gallery.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-tabwidget.html">TabWidget</a><br/>
<a href="hello-tabwidget.html"><img src="images/hello-tabwidget.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-mapview.html">MapView</a><br/>
<a href="hello-mapview.html"><img src="images/hello-mapview.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-webview.html">WebView</a><br/>
<a href="hello-webview.html"><img src="images/hello-webview.png" height="285" width="200" /></a>
</div>
<!--
TODO
<div class="view">
<a href="hello-popupwindow.html">PopupWindow<br/>
<img src="images/hello-popupwindow.png" height="285" width="200" /></a>
</div>
<div class="view">
<a href="hello-tabhost.html">TabHost / TabWidget<br/>
<img src="images/hello-tabhost.png" height="285" width="200" /></a>
</div>
ProgressBar; RatingBar; FrameLayout
-->
<p class="note" style="clear:left">
There are plenty more Views and widgets available. See the {@link android.view.View} class
for more on View layouts, and the {@link android.widget widget package}
for more useful widgets. And for more raw code samples, visit the
<a href="{@docRoot}guide/samples/ApiDemos/src/com/example/android/apis/view/index.html">Api Demos</a>.
These can also be found offline, in <code>/&lt;sdk&gt;/samples/ApiDemos</code>.</p>
</div>