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page.title=Common Tasks and How to Do Them in Android
parent.title=FAQs, Tips, and How-to
parent.link=index.html
@jd:body
<ul>
<li><a href="#neweclipseandroidproject">Creating an Android Application using
the Eclipse plugin</a></li>
<li><a href="#newandroidprojectnoeclipse">Creating an Android Application without
the Eclipse plugin</a></li>
<li><a href="#addexternallibrary">Adding an External Library (.jar) using Eclipse</a></li>
<li><a href="#implementcallbacks">Implementing Activity callbacks</a> (Android
calls your activity at various key moments in its life cycle. You must know
how to handle each of these to draw your screen, initialize class members,
and acquire data.)</li>
<li><a href="#opennewscreen">Opening a new screen</a></li>
<li><a href="#listening">Listening for button clicks </a></li>
<li><a href="#configurewindowproperties">Configuring general window properties </a></li>
<li><a href="#localhostalias">Referring to localhost from the emulated environment</a></li>
<li><a href="#appstate">Storing and retrieving state</a></li>
<li><a href="{@docRoot}guide/topics/data/data-storage.html#preferences">Storing and retrieving preferences</a></li>
<li><a href="#storingandretrieving">Storing and retrieving larger or more complex
persistent data</a> (files and data) </li>
<li><a href="#playback">Playing audio, video, still, or other media files</a></li>
<li><a href="#broadcastreceivers">Listening for and broadcasting global messages
and setting alarms</a></li>
<li><a href="#alerts">Displaying alerts </a></li>
<li><a href="#progressbar">Displaying a progress bar</a> </li>
<li><a href="#addmenuitems">Adding items to the screen menu</a> </li>
<li><a href="#webpage">Display a web page</a> </li>
<li><a href="#binding">Binding to data</a></li>
<li><a href="#handle">Getting a Handle to a Screen Element</a></li>
<li><a href="#captureimages">Capture images from the phone camera </a></li>
<li><a href="#threading">Handling expensive operations in the UI thread</a></li>
<li><a href="#selectingtext">Selecting, highlighting, or styling portions of
text</a></li>
<li><a href="#querymap">Utilizing attributes in a Map query</a></li>
<li><a href="#filelist">List of files for an Android application</a></li>
<li><a href="#logging">Print messages to a log file</a></li>
</ul>
<p>The ApiDemos sample application includes many, many examples of common
tasks and UI features. See the code inside
<code>&lt;sdk&gt;samples/ApiDemos</code> and the other sample applications
under the <code>samples/</code> folder in the SDK.</p>
<h2 id="neweclipseandroidproject">Creating an Android Application using the Eclipse Plugin</h2>
<p>Using the Android Eclipse plugin is the fastest and easiest way
to start creating a new Android application. The plugin automatically generates
the correct project structure for your application, and keeps the resources
compiled for you automatically.</p>
<p>It is still a good idea to know what is going on though. Take a look at <a
href="{@docRoot}guide/topics/fundamentals.html">Application Fundamentals</a>
to understand the basics of how an Android application works.</p>
<p>You should also take a look at the ApiDemos application and the other sample
applications included in the SDK, in the <code>&lt;sdk&gt;/samples/</code>
folder in the SDK.</p>
<p>Finally, a great way to started with Android development in Eclipse is to
follow both the <a href="{@docRoot}resources/tutorials/hello-world.html">Hello,
World</a> and <a
href="{@docRoot}resources/tutorials/notepad/index.html">Notepad</a> code
tutorials. In particular, the start of the Hello Android tutorial is an
excellent introduction to creating a new Android application in Eclipse.</p>
<h2 id="newandroidprojectnoeclipse">Creating an Android Application without the Eclipse Plugin</h2>
<p>This topic describes the manual steps in creating an Android application.
Before reading this, you should read <a
href="{@docRoot}guide/topics/fundamentals.html">Application Fundamentals</a>
to understand the basics of how an Android application works. You might also
want to look at the sample code included with the Android SDK, in the
<code>&lt;sdk&gt;/samples/</code> directory. </p>
<p>Here is a list of the basic steps in building an application.</p>
<ol>
<li><strong>Create your required resource files</strong> &nbsp;&nbsp;This includes
the AndroidManifest.xml global description file, string files that your application
needs, and layout files describing your user interface. A full list of optional
and required files and syntax details for each is given in <a href="#filelist">File
List for an Android Application</a>. </li>
<li><strong>Design your user interface</strong> &nbsp;&nbsp;See <a
href="{@docRoot}guide/topics/ui/index.html">User Interface</a> for
details on elements of the Android screen. </li>
<li><strong>Implement your Activity </strong>(this page)<strong>&nbsp;&nbsp; </strong> You
will create one class/file for each screen in your application. Screens will
inherit from an {@link android.app android.app} class, typically {@link android.app.Activity
android.app.Activity} for basic screens, {@link android.app.ListActivity
android.app.ListActivity} for list screens, or {@link android.app.Dialog
android.app.Dialog} for dialog boxes. You will implement the required callbacks
that let you draw your screen, query data, and commit changes, and also perform
any required tasks such as opening additional screens or reading data from
the device. Common tasks, such as opening a new screen or reading data from
the device, are described below.
The list of files you'll need for your application are described in <a href="#filelist">List
of Files for an Android Application</a>. </li>
<li><strong><a href="{@docRoot}guide/developing/other-ide.html#buildingwithant">Build and install your
package</a>.</strong> The Android SDK has some nice tools for generating
projects and debugging code. </li>
</ol>
<h2 id="addexternallibrary">Adding an External Library (.jar) using Eclipse</h2>
<p>
You can use a third party JAR in your application by adding it to your Eclipse project as follows:
</p>
<ol>
<li>
In the <strong>Package Explorer</strong> panel, right-click on your project and select <strong>Properties</strong>.
<li>
Select <strong>Java Build Path</strong>, then the tab <strong>Libraries</strong>.
<li>
Press the <strong>Add External JARs...</strong> button and select the JAR file.
</ol>
<p>
Alternatively, if you want to include third party JARs with your package, create a new directory for them within your project and select <strong>Add Library...</strong> instead.</p>
<p>
It is not necessary to put external JARs in the assets folder.
</p>
<a name="implementcallbacks" id="implementcallbacks"></a>
<h2>Implementing Activity Callbacks</h2>
<p>Android calls a number of callbacks to let you draw your screen, store data before
pausing, and refresh data after closing. You must implement at least some of
these methods. See <a href="{@docRoot}guide/topics/fundamentals.html#lcycles">Lifecycles</a>
discussion in Application Fundamentals to learn when and in what order these methods
are called. Here are some of the standard types of screen classes that Android provides:</p>
<ul>
<li>{@link android.app.Activity android.app.Activity} - This is a standard screen,
with no specialization.</li>
<li>{@link android.app.ListActivity android.app.ListActivity} - This is a screen
that is used to display a list of something. It hosts a ListView object,
and exposes methods to let you identify the selected item, receive callbacks
when the selected item changes, and perform other list-related actions. </li>
<li>{@link android.app.Dialog android.app.Dialog} - This is a small, popup dialog-style
window that isn't intended to remain in the history stack. (It is not resizeable
or moveable by the user.)</li>
</ul>
<a name="opennewscreen" id="opennewscreen"></a><h2>Opening a New Screen</h2>
<p>Your Activity will often need to open another Activity screen as it progresses.
This new screen can be part of the same application or part of another application,
the new screen can be floating or full screen, it can return a result, and you
can decide whether to close this screen and remove it from the history stack
when you are done with it, or to keep the screen open in history. These next
sections describe all these options. </p>
<h3>Floating or full?<a name="floatingorfull" id="floatingorfull"></a></h3>
<p>When you open a new screen you can decide whether to make it transparent or floating,
or full-screen. The choice of new screen affects the event sequence of events
in the old screen (if the new screen obscures the old screen, a different
series of events is called in the old screen). See <a
href="{@docRoot}guide/topics/fundamentals.html#lcycles">Lifecycles</a> discussion
in Application Fundamentals for details. </p>
<p>Transparent or floating windows are implemented in three
standard ways: </p>
<ul>
<li>Create an {@link android.app.Dialog app.Dialog} class </li>
<li>Create an {@link android.app.AlertDialog app.AlertDialog} class </li>
<li>Set the {@link android.R.style#Theme_Dialog} <em>theme</em> attribute to <code>&#64;android:style/Theme.Dialog</code>
in your AndroidManifest.xml file. For example:
<pre>&lt;activity class=&quot;AddRssItem&quot; android:label=&quot;Add an item&quot; android:theme=&quot;&#064;android:style/Theme.Dialog&quot;/&gt;</pre></li>
</ul>
<p>Calling startActivity() or startActivityForResult() will open a new screen in whatever
way it defines itself (if it uses a floating theme it will be floating,
otherwise it will be full screen). </p>
<h3>Opening a Screen </h3>
<p>When you want to open a new screen, you can either explicitly specify the activity
class to open, or you can let the operating system decide which screen to open,
based upon the data and various parameters you pass in. A screen is opened by
calling {@link android.app.Activity#startActivity(android.content.Intent) startActivity}
and passing in an {@link android.content.Intent Intent} object, which specifies
the criteria for the handling screen. To specify a specific screen, call Intent.setClass
or setClassName with the exact activity class to open. Otherwise, set a variety
of values and data, and let Android decide which screen is appropriate to open.
Android will find one or zero Activities that match the specified requirements;
it will never open multiple activities for a single request. More information
on Intents and how Android resolves them to a specific class is given in the
{@link android.content.Intent Intent} topic. </p>
<a name="intentexamples" id="intentexamples"></a><h3>Some Intent examples </h3>
<p>The following snippet loads the com.android.samples.Animation1 class, and
passes it some arbitrary data.:</p>
<pre>Intent myIntent = new Intent();
myIntent.setClassName(&quot;com.android.samples&quot;, &quot;com.android.samples.Animation1&quot;);
myIntent.putExtra(&quot;com.android.samples.SpecialValue&quot;, &quot;Hello, Joe!&quot;); // key/value pair, where key needs current package prefix.
startActivity(myIntent); </pre>
<p>The next snippet requests that a Web page be opened by specifying the VIEW action,
and a URI data string starting with &quot;http://&quot; schema:</p>
<pre>Intent myIntent = new Intent(Intent.VIEW_ACTION, Uri.parse(&quot;http://www.google.com&quot;));</pre>
<p>Here is the intent filter from the AndroidManifest.xml file for com.android.browser:</p>
<pre>&lt;intent-filter&gt;
&lt;action android:name=&quot;android.intent.action.VIEW&quot; /&gt;
&lt;category android:name=&quot;android.intent.category.DEFAULT&quot; /&gt;
&lt;scheme android:name=&quot;http&quot; /&gt;
&lt;scheme android:name=&quot;https&quot; /&gt;
&lt;scheme android:name=&quot;file&quot; /&gt;
&lt;/intent-filter&gt; </pre>
<p>Android defines a number of standard values, for instance the action constants
defined by {@link android.content.Intent}. You can define custom values, but
both the caller and handler must use them. See the &lt;intent-filter&gt;
tag description in <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">The AndroidManifest.xml
File</a> for more information on the manifest syntax for the handling
application. </p>
<a name="returningaresult" id="returningaresult"></a><h3>Returning a Result from a Screen</h3>
<p>A window can return a result after it closes. This result will be passed back
into the calling Activity's {@link android.app.Activity#onActivityResult(int,int,android.content.Intent)
onActivityResult()} method, which can supply an Intent containing arbitrary data, along with
the request code passed to startActivityForResult(). Note that you must call the {@link
android.app.Activity#startActivityForResult(android.content.Intent,int) startActivityForResult()}
method that accepts a request code parameter to get this callback. The following
code demonstrates opening a new screen and retrieving a result. </p>
<pre>// Open the new screen.
public void onClick(View v){
// Start the activity whose result we want to retrieve. The
// result will come back with request code GET_CODE.
Intent intent = new Intent(this, com.example.app.ChooseYourBoxer.class);
startActivityForResult(intent, CHOOSE_FIGHTER);
}
// Listen for results.
protected void onActivityResult(int requestCode, int resultCode, Intent data){
// See which child activity is calling us back.
switch (resultCode) {
case CHOOSE_FIGHTER:
// This is the standard resultCode that is sent back if the
// activity crashed or didn't doesn't supply an explicit result.
if (resultCode == RESULT_CANCELED){
myMessageboxFunction("Fight cancelled");
}
else {
myFightFunction(data);
}
default:
break;
}
}
// Class SentResult
// Temporary screen to let the user choose something.
private OnClickListener mLincolnListener = new OnClickListener(){
public void onClick(View v) {
Bundle stats = new Bundle();
stats.putString("height","6\'4\"");
stats.putString("weight", "190 lbs");
stats.putString("reach", "74\"");
setResult(RESULT_OK, "Lincoln", stats);
finish();
}
};
private OnClickListener mWashingtonListener = new OnClickListener() {
public void onClick(View v){
Bundle stats = new Bundle();
stats.putString("height","6\'2\"");
stats.putString("weight", "190 lbs");
stats.putString("reach", "73\"");
setResult(RESULT_OK, "Washington", Bundle);
finish();
}
};
</pre>
<h3>Lifetime of the new screen </h3>
<p>An activity can remove itself from the history stack by calling {@link android.app.Activity#finish()
Activity.finish()} on itself, or the activity that opened the screen can call
{@link android.app.Activity#finishActivity(int) Activity.finishActivity()}
on any screens that it opens to close them. </p>
<a name="listening" id="listening"></a><h2>Listening for Button Clicks</h2>
<p>Button click and other UI event capturing are covered in <a href="{@docRoot}guide/topics/ui/ui-events.html">Handling UI Events</a> on the UI Design page.</p>
<a name="configurewindowproperties" id="configurewindowproperties"></a><h2>Configuring General Window Properties</h2>
<p>You can set a number of general window properties, such as whether to display
a title, whether the window is floating, and whether it displays an icon, by
calling methods on the {@link android.view.Window Window} member
of the underlying View object for the window. Examples include calling {@link
android.app.Activity#getWindow() getWindow().requestFeature()} (or the convenience
method {@link android.app.Activity#requestWindowFeature(int) requestWindowFeature(<em>some_feature</em>)})
to hide the title. Here is an example of hiding the title bar:</p>
<pre>//Hide the title bar
requestWindowFeature(Window.FEATURE_NO_TITLE);
</pre>
<p>A better way to achieve the same end is to specify a theme in your Android
Manifest file:</p>
<pre>&lt;application android:icon="@drawable/icon" android:theme="@android:style/Theme.NoTitleBar"&gt;
</pre>
<p>This is preferable because it tells the system not to show a title bar while
your application is starting up. With the explicit method call, your application
will have a title bar visible to the user until <code>onCreate</code> runs.</p>
<p>(Note that this can be applied to either the <code>&lt;application&gt;</code>
tag or to individual <code>&lt;activity&gt;</code> tags.)</p>
<a name="localhostalias" id="localhostalias"></a><h2>Referring to localhost from the emulated environment</h2>
<p>
If you need to refer to your host computer's <em>localhost</em>, such as when you
want the emulator client to contact a server running on the same host, use the alias
<code>10.0.2.2</code> to refer to the host computer's loopback interface.
From the emulator's perspective, localhost (<code>127.0.0.1</code>) refers to its own
loopback interface.
</p>
<a name="appstate" id="appstate"></a><h2>Storing and Retrieving State</h2>
<p>If your application is dumped from memory because of space concerns, it will lose
all user interface state information such as checkbox state and text box values
as well as class member values. Android calls {@link android.app.Activity#onSaveInstanceState(android.os.Bundle)
Activity.onSaveInstanceState} before it pauses the application. This method hands in a {@link
android.os.Bundle Bundle} that can be used to store name/value pairs that will
persist and be handed back to the application even if it is dropped from memory.
Android will pass this Bundle back to you when it calls {@link android.app.Activity#onCreate(android.os.Bundle)
onCreate()}. This Bundle only exists while the application is still in the history
stack (whether or not it has been removed from memory) and will be lost when
the application is finalized. See the topics for {@link android.app.Activity#onSaveInstanceState} and
{@link android.app.Activity#onCreate} for
examples of storing and retrieving state.</p>
<p>Read more about the lifecycle of an application in <a href="{@docRoot}guide/topics/fundamentals.html">Application Fundamentals</a>.</p>
<h3>Storing and Retrieving Larger or More Complex Persistent Data<a name="storingandretrieving" id="storingandretrieving"></a></h3>
<p>Your application can store files or complex collection objects, and reserve them
for private use by itself or other activities in the application, or it can expose
its data to all other applications on the device. See <a href="{@docRoot}guide/topics/data/data-storage.html">Storing,
Retrieving, and Exposing Data</a> to learn how to store and retrieve private data,
how to store and retrieve common data from the device, and how to expose your
private data to other applications.</p>
<a name="playback" id="playback"></a><h2>Playing Media Files</h2>
<p>Please see the document <a href="{@docRoot}guide/topics/media/index.html">Audio and Video</a> for more details.</p>
<a name="broadcastreceivers" id="broadcastreceivers"></a><h2>Listening For and Broadcasting Global Messages, and Setting Alarms</h2>
<p>You can create a listening class that can be notified or even instantiated whenever
a specific type of system message is sent.
</p>
<p>The listening classes, called broadcast receivers, extend {@link android.content.BroadcastReceiver
BroadcastReceiver}. If you want Android to instantiate the object whenever an appropriate
intent notification is sent, define the receiver with a <code>&lt;receiver&gt;</code> element
in the AndroidManifext.xml file. If the caller is expected to instantiate the
object in preparation to receive a message, this is not required. The receiver
will get a call to their {@link android.content.BroadcastReceiver#onReceive(android.content.Context,android.content.Intent)
BroadcastReceiver.onReceive()} method. A receiver can define an <code>&lt;intent-filter&gt;</code> tag
that describes the types of messages it will receive. Just as Android's IntentResolver
will look for appropriate Activity matches for a startActivity() call, it will
look for any matching Receivers (but it will send the message to all matching
receivers, not to the &quot;best&quot; match). </p>
<p>To send a notification, the caller creates an {@link android.content.Intent Intent}
object and calls {@link android.app.Activity#sendBroadcast(android.content.Intent)
Context.sendBroadcast()} with that Intent. Multiple recipients can receive
the same message. You can broadcast an Intent message to an intent receiver in
any application, not only your own. If the receiving class is not registered
using <code>&lt;receiver&gt;</code> in its manifest, you can dynamically instantiate
and register a receiver by calling {@link android.content.Context#registerReceiver(android.content.BroadcastReceiver,android.content.IntentFilter)
Context.registerReceiver()}. </p>
<p>Receivers can include intent filters to specify what kinds of intents they are
listening for. Alternatively, if you expect a single known caller to contact
a single known receiver, the receiver does not specify an intent filter, and
the caller specifies the receiver's class name in the Intent by calling {@link
android.content.Intent#setClassName(java.lang.String, java.lang.String) Intent.setClassName()}
with the recipient's class name. The recipient receives a {@link android.content.Context
Context} object that refers to its own package, not to the package of the sender.</p>
<p><em><strong>Note:</strong></em>&nbsp;&nbsp;&nbsp;If a receiver or broadcaster
enforces permissions, your application might need to request permission
to send or receive messages from that object. You can request permission by using
the &lt;uses-permission&gt; tag in the manifest. </p>
<p>Here is a code snippet of a sender and receiver. This example does not demonstrate
registering receivers dynamically. For a full code example, see the AlarmService
class in the ApiDemos project.</p>
<h3>Sending the message</h3>
<pre>// We are sending this to a specific recipient, so we will
// only specify the recipient class name.
Intent intent = new Intent(this, AlarmReceiver.class);
intent.putExtra(&quot;message&quot;,&quot;Wake up.&quot;);
sendBroadcast(intent);
</pre>
<h3>Receiving the message</h3>
<p><strong>Receiver AndroidManifest.xml </strong>(because there is no intent filter
child, this class will only receive a broadcast when the receiver class is specified
by name, as is done in this example):</p>
<pre>
&lt;receiver class=".AlarmReceiver" /&gt;</pre>
<p><strong>Receiver Java code: </strong></p>
<pre>
public class AlarmReceiver extends BroadcastReceiver{
// Display an alert that we've received a message.
&#064;Override
public void onReceive(Context context, Intent intent){
// Send a text notification to the screen.
NotificationManager nm = (NotificationManager)
context.getSystemService(Context.NOTIFICATION_SERVICE);
nm.notifyWithText(R.id.alarm,
&quot;Alarm!!!&quot;,
NotificationManager.LENGTH_SHORT,
null);
}
} </pre>
<h3>Other system messages</h3>
<p>You can listen for other system messages sent by Android as well, such as USB
connection/removal messages, SMS arrival messages, and timezone changes. See
{@link android.content.Intent} for a list of broadcast messages to listen for.
Messages are marked &quot;Broadcast Action&quot; in the documentation. </p>
<h3>Listening for phone events<a name="phoneevents" id="phoneevents"></a></h3>
<p>The {@link android.telephony android.telephony} package overview page describes how to
register to listen for phone events. </p>
<a name="alarms" id="alarms"></a><h3>Setting Alarms </h3>
<p>Android provides an {@link android.app.AlarmManager AlarmManager} service that
will let you specify an Intent to send at a designated time. This intent is typically
used to start an application at a preset time. (Note: If you want to send
a notification to a sleeping or running application, use {@link android.os.Handler
Handler} instead.)</p>
<a name="alerts" id="alerts"></a><h2>Displaying Alerts</h2>
<p>There are two major kinds of alerts that you may display to the user:
(1) Normal alerts are displayed in response to a user action, such as
trying to perform an action that is not allowed. (2) Out-of-band alerts,
called notifications, are
displayed as a result of something happening in the background, such as the
user receiving new e-mail.</p>
<a name="dialogsandalerts" id="dialogsandalerts"></a><h3>Normal Alerts</h3>
<p>Android provides a number of ways for you to show popup notifications to your
user as they interact with your application. </p>
<table width="100%" border="1">
<tr>
<th scope="col">Class</th>
<th scope="col">Description</th>
</tr>
<tr>
<td>{@link android.app.Dialog app.Dialog}</td>
<td>A generic floating dialog box with a layout that you design. </td>
</tr>
<tr>
<td><p>{@link android.app.AlertDialog app.AlertDialog}</p></td>
<td>A popup alert dialog with two buttons (typically OK and Cancel) that
take callback handlers. See the section after this table for more details. </td>
</tr>
<tr>
<td>{@link android.app.ProgressDialog ProgressDialog} </td>
<td>A dialog box used to indicate progress of an operation with a known progress
value or an indeterminate length (setProgress(bool)). See <strong>Views</strong> &gt; <strong>Progress Bar</strong> in
ApiDemos for examples. </td>
</tr>
<tr>
<td>Activity</td>
<td>By setting the theme of an activity to
{@link android.R.style#Theme_Dialog
android:theme=&quot;&#064;android:style/Theme.Dialog&quot;},
your activity will take on
the appearance of a normal dialog, floating on top of whatever was
underneath it. You usually set the theme through the
{@link android.R.attr#theme android:theme} attribute in your AndroidManifest.xml.
The advantage of this
over Dialog and AlertDialog is that Application has a much better managed
life cycle than dialogs: if a dialog goes to the background and is killed,
you cannot recapture state, whereas Application exposes a {@link android.os.Bundle
Bundle} of saved values in <code>onCreate()</code> to help you maintain state.</td>
</tr>
</table>
<h3>AlertDialog</h3>
<p>This is a basic warning dialog box that lets you configure a message, button text,
and callback. You can create one by calling using the {@link
android.app.AlertDialog.Builder} class, as shown here. </p>
<pre>private Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case ACCEPT_CALL:
answer(msg.obj);
break;
case BOUNCE_TO_VOICEMAIL:
voicemail(msg.obj);
break;
}
}
};
private void IncomingMotherInlawCall(Connection c) {
String Text;
// &quot;Answer&quot; callback.
Message acceptMsg = Message.obtain();
acceptMsg.target = mHandler;
acceptMsg.what = ACCEPT_CALL;
acceptMsg.obj = c.getCall();
// &quot;Cancel&quot; callback.
final Message rejectMsg = Message.obtain();
rejectMsg.target = mHandler;
rejectMsg.what = BOUNCE_TO_VOICEMAIL;
rejectMsg.obj = c.getCall();
new AlertDialog.Builder(this)
.setMessage("Phyllis is calling")
.setPositiveButton("Answer", acceptMsg)
.setOnCanceListener(new OnCancelListener() {
public void onCancel(DialogInterface dialog) {
rejectMsg.sendToTarget();
}});
.show();
} </pre>
<h3>Notifications</h3>
<p>Out-of-band alerts should always be displayed using the
{@link android.app.NotificationManager}, which allows you to tell the user
about something they may be interested in without disrupting what they are
currently doing. A notification can be anything from a brief pop-up box
informing the user of the new information, through displaying a persistent
icon in the status bar, to vibrating, playing sounds, or flashing lights to
get the user's attention. In all cases, the user must explicitly shift their
focus to the notification before they can interact with it.</p>
<p>The following code demonstrates using NotificationManager to display a basic text
popup when a new SMS message arrives in a listening service, and provides the
current message count. You can see several more examples in the ApiDemos application,
under app/ (named <em>notification</em>*.java).</p>
<pre>static void setNewMessageIndicator(Context context, int messageCount){
// Get the static global NotificationManager object.
NotificationManager nm = NotificationManager.getDefault();</p>
// If we're being called because a new message has been received,
// then display an icon and a count. Otherwise, delete the persistent
// message.
if (messageCount &gt; 0) {
nm.notifyWithText(myApp.NOTIFICATION_GUID, // ID for this notification.
messageCount + &quot; new message&quot; + messageCount &gt; 1 ? &quot;s&quot;:&quot;&quot;, // Text to display.
NotificationManager.LENGTH_SHORT); // Show it for a short time only.
}
}</pre>
<p>To display a notification in the status bar and have it launch an intent when
the user selects it (such as the new text message notification does), call {@link
android.app.NotificationManager#notify(int, android.app.Notification) NotificationManager.notify()},
and pass in vibration patterns, status bar icons, or Intents to associate with
the notification. </p>
<a name="progressbar" id="progressbar"></a><h2>Displaying a Progress Bar</h2>
<p>An activity can display a progress bar to notify the user that something is happening.
To display a progress bar in a screen, call {@link android.app.Activity#requestWindowFeature(int)
Activity.requestWindowFeature(Window.FEATURE_PROGRESS)}. To set the value
of the progress bar, call {@link android.view.Window#setFeatureInt(int,int)
Activity.getWindow().setFeatureInt(Window.FEATURE_PROGRESS, <em>level</em>)}.
Progress bar values are from 0 to 9,999, or set the value to 10,000 to make the
progress bar invisible. </p>
<p>You can also use the {@link android.app.ProgressDialog ProgressDialog} class,
which enables a dialog box with an embedded progress bar to send a &quot;I'm working
on it&quot; notification to the user. </p>
<a name="addmenuitems" id="addmenuitems"></a><h2>Adding Items to the Screen Menu</h2>
<p>See <a href="{@docRoot}guide/topics/ui/menus.html">Creating Menus</a>.</p>
<a name="webpage" id="webpage"></a><h2>Display a Web Page</h2>
<p>Use the {@link android.webkit.WebView webkit.WebView} object. </p>
<a name="binding" id="binding"></a><h2>Binding to Data</h2>
<p>You can bind a ListView to a set of underlying data by using a shim class called
{@link android.widget.ListAdapter ListAdapter} (or a subclass). ListAdapter subclasses
bind to a variety of data sources, and expose a common set of methods such as
getItem() and getView(), and uses them to pick View items to display in its list.
You can extend ListAdapter and override getView() to create your own custom list
items. There are essentially only two steps you need to perform to bind to data: </p>
<ol>
<li>Create a ListAdapter object and specify its data source</li>
<li>Give the ListAdapter to your ListView object.</li>
</ol>
<p>That's it!</p>
<p>Here's an example of binding a ListActivity screen to the results from a cursor
query. (Note that the setListAdapter() method shown is a convenience method that
gets the page's ListView object and calls setAdapter() on it.)</p>
<pre>// Run a query and get a Cursor pointing to the results.
Cursor c = People.query(this.getContentResolver(), null);
startManagingCursor(c);
// Create the ListAdapter. A SimpleCursorAdapter lets you specify two interesting things:
// an XML template for your list item, and
// The column to map to a specific item, by ID, in your template.
ListAdapter adapter = new SimpleCursorAdapter(this,
android.R.layout.simple_list_item_1, // Use a template that displays a text view
c, // Give the cursor to the list adapter
new String[] {People.NAME} , // Map the NAME column in the people database to...
new String[] {"text1"}); // The "text1" view defined in the XML template
setListAdapter(adapter);</pre>
<p>See view/List4 in the ApiDemos project for an example of extending ListAdapter
for a new data type. </p>
<a name="handle"></a>
<h2>Getting a Handle to a Screen Element</h2>
<p>You can get a handle to a screen element by calling {@link
android.app.Activity#findViewById(int) Activity.findViewById}. You can then use
the handle to set or retrieve any values exposed by the object. </p>
<a name="captureimages" id="captureimages"></a><h2>Capture Images from the Phone Camera</h2>
<p>You can hook into the device's camera onto your own Canvas object by using the
{@link android.hardware.Camera Camera} class. See that class's documentation,
and the ApiDemos project's Camera Preview application (Graphics/Camera Preview)
for example code. </p>
<a name="threading" id="threading"></a><h2>Handling Expensive Operations in the UI Thread</h2>
<p>Avoid performing long-running operations (such as network I/O) directly in the UI thread &mdash;
the main thread of an application where the UI is run &mdash; or your application may be blocked
and become unresponsive. Here is a brief summary of the recommended approach for handling expensive operations:</p>
<ol>
<li>Create a Handler object in your UI thread</li>
<li>Spawn off worker threads to perform any required expensive operations</li>
<li>Post results from a worker thread back to the UI thread's handler either through a Runnable or a {@link android.os.Message}</li>
<li>Update the views on the UI thread as needed</li>
</ol>
<p>The following outline illustrates a typical implementation:</p>
<pre>
public class MyActivity extends Activity {
[ . . . ]
// Need handler for callbacks to the UI thread
final Handler mHandler = new Handler();
// Create runnable for posting
final Runnable mUpdateResults = new Runnable() {
public void run() {
updateResultsInUi();
}
};
&#64;Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
[ . . . ]
}
protected void startLongRunningOperation() {
// Fire off a thread to do some work that we shouldn't do directly in the UI thread
Thread t = new Thread() {
public void run() {
mResults = doSomethingExpensive();
mHandler.post(mUpdateResults);
}
};
t.start();
}
private void updateResultsInUi() {
// Back in the UI thread -- update our UI elements based on the data in mResults
[ . . . ]
}
}
</pre>
<p>For further discussions on this topic, see
<a href="{@docRoot}guide/practices/design/responsiveness.html">Designing for Responsiveness</a>
and the {@link android.os.Handler} documentation.</p>
<a name="selectingtext" id="selectingtext"></a><h2>Selecting, Highlighting, or Styling Portions of Text</h2>
<p>You can highlight or style the formatting of strings or substrings of text in
a TextView object. There are two ways to do this:</p>
<ul>
<li>If you use a <a href="{@docRoot}guide/topics/resources/available-resources.html#stringresources">string resource</a>,
you can add some simple styling, such as bold or italic using HTML notation.
The currently supported tags are: <code>B</code> (bold),
<code>I</code> (italic), <code>U</code> (underline),
<code>TT</code> (monospace), <code>BIG</code>, <code>SMALL</code>,
<code>SUP</code> (superscript), <code>SUB</code> (subscript),
and <code>STRIKE</code> (strikethrough).
So, for example, in res/values/strings.xml you could declare this:<br />
<code>&lt;resource&gt;<br />
&nbsp;&nbsp;&nbsp;&nbsp;&lt;string&nbsp;id=&quot;@+id/styled_welcome_message&quot;&gt;We
are &lt;b&gt;&lt;i&gt;so&lt;/i&gt;&lt;/b&gt; glad to see you.&lt;/string&gt;<br />
&lt;/resources&gt;</code></li>
<li>To style text on the fly, or to add highlighting or more complex styling,
you must use the Spannable object as described next. </li>
</ul>
<p>To style text on the fly, you must make sure the TextView is using {@link android.text.Spannable}
storage for the text (this will always be true if the TextView is an EditText),
retrieve its text with {@link android.widget.TextView#getText}, and call {@link
android.text.Spannable#setSpan}, passing in a new style class from the {@link
android.text.style} package and the selection range. </p>
<p>The following code snippet demonstrates creating a string with a highlighted section,
italic section, and bold section, and adding it to an EditText object. </p>
<pre>// Get our EditText object.
EditText vw = (EditText)findViewById(R.id.text);
// Set the EditText's text.
vw.setText("Italic, highlighted, bold.");
// If this were just a TextView, we could do:
// vw.setText("Italic, highlighted, bold.", TextView.BufferType.SPANNABLE);
// to force it to use Spannable storage so styles can be attached.
// Or we could specify that in the XML.
// Get the EditText's internal text storage
Spannable str = vw.getText();
// Create our span sections, and assign a format to each.
str.setSpan(new StyleSpan(android.graphics.Typeface.ITALIC), 0, 7, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
str.setSpan(new BackgroundColorSpan(0xFFFFFF00), 8, 19, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
str.setSpan(new StyleSpan(android.graphics.Typeface.BOLD), 21, str.length() - 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
</pre>
<a name="querymap" id="querymap"></a><h2>Utilizing attributes in a Map query</h2>
<p>
When using a search intent to ask the Maps activity to search for something, the Maps activity responds to the following attributes in the optional context bundle:
</p>
<pre>
float "centerLatitude" default 0.0f
float "centerLongitude" default 0.0f
float "latitudeSpan" default 0.0f
float "longitudeSpan" default 0.0f
int "zoomLevel" default 10
</pre>
<p>
This context information is used to center the search result in a particular area, and is equivalent to adjusting the Map activity to the described location and zoom level before issuing the query.
</p>
<p>
If the latitudeSpan, longitudeSpan, and zoomLevel attributes are not consistent, then it is undefined which one takes precedence.
</p>
<a name="filelist" id="filelist"></a><h2>List of Files for an Android Application</h2>
<p>The following list describes the structure and files of an Android application.
Many of these files can be built for you (or stubbed out) by the android tool
shipped in the tools/ menu of the SDK. </p>
<table width="100%" border="0">
<tr>
<td width="28%" valign="top">MyApp/<br /></td>
<td width="72%" valign="top">&nbsp;</td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;AndroidManifest.xml</td>
<td valign="top">(<em>required</em>) Advertises the screens that this application provides,
where they can be launched (from the main program menu or elsewhere),
any content providers it implements and what kind of data they handle,
where the implementation classes are, and other application-wide
information. Syntax details for this file are described in <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">The AndroidManifest.xml File</a>.</td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;src/<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/<em>myPackagePath</em>/.../<em>MyClass</em>.java</td>
<td valign="top">(<em>required</em>) This folder holds all the source code files for your
application, inside the appropriate package subfolders. </td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;res/</td>
<td valign="top">(<em>required</em>) This folder holds all the <em>resources</em> for
your application. Resources are external data files or description files
that are compiled into your code at build time. Files in different folders
are compiled differently, so you must put the proper resource into the
proper folder. (See <a href="{@docRoot}guide/topics/resources/resources-i18n.html">Resources</a> for details.)</td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;anim/<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>animation1</em>.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>...</em></td>
<td valign="top">(<em>optional</em>) Holds any animation XML description files that the
application uses. The format of these files is described in <a href="{@docRoot}guide/topics/resources/resources-i18n.html">Resources</a>. </td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;drawable/<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>some_picture</em>.png<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>some_stretchable</em>.9.png<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>some_background</em>.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...</td>
<td valign="top">(<em>optional</em>) Zero or more files that will be compiled to {@link
android.graphics.drawable android.graphics.drawable} resources. Files
can be image files (png, gif, or other) or XML files describing other
graphics such as bitmaps, stretchable bitmaps, or gradients. Supported
bitmap file formats are PNG (preferred), JPG, and GIF (discouraged),
as well as the custom 9-patch stretchable bitmap format. These formats
are described in <a href="{@docRoot}guide/topics/resources/resources-i18n.html">Resources</a>. </td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;layout/<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<em>screen_1_layout</em>.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...<br /></td>
<td valign="top">(<em>optional</em>) Holds all the XML files describing screens or parts
of screens. Although you could create a screen in Java, defining them
in XML files is typically easier. A layout file is similar in concept
to an HTML file that describes the screen layout and components. See <a href="{@docRoot}guide/topics/ui/index.html">User Interface</a> for more information about designing screens, and <a href="{@docRoot}guide/topics/resources/available-resources.html#layoutresources">Available Resource Types</a> for the syntax of these files.</td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;values/<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;arrays<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;classes.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;colors.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dimens.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; strings.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;styles.xml<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;values.xml<br /></td>
<td valign="top"><p>(<em>optional</em>) XML files describing additional resources
such as strings, colors, and styles. The naming, quantity, and number
of these files are not enforced--any XML file is compiled, but these
are the standard names given to these files. However, the syntax
of these files is prescribed by Android, and described in <a href="{@docRoot}guide/topics/resources/resources-i18n.html">Resources</a>. </p>
</td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;xml/</td>
<td valign="top">(<em>optional</em>) XML files that can be read at run time on the device. </td>
</tr>
<tr>
<td valign="top">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;raw/</td>
<td valign="top">(<em>optional</em>) Any files to be copied directly to the device. </td>
</tr>
</table>
<a name="logging" ></a>
<h2>Print Messages to a Log File</h2>
<p>To write log messages from your application:</p>
<ol><li>Import <code>android.util.Log</code>.</li>
<li>Use <code>Log.v()</code>, <code>Log.d()</code>, <code>Log.i()</code>,
<code>Log.w()</code>, or <code>Log.e()</code> to log messages.
(See the {@link android.util.Log} class.)<br/> E.g.,
<code>Log.e(this.toString(), "error: " + err.toString())</code></li>
<li>Launch <a href="{@docRoot}guide/developing/tools/ddms.html">DDMS</a> from a terminal
by executing <code>ddms</code> in your Android SDK <code>/tools</code> path.</li>
<li>Run your application in the Android emulator.</li>
<li>From the DDMS application, select the emulator
(e.g., "emulator-5554") and click <b>Device > Run logcat...</b>
to view all the log data.</li>
</ol>
<p class="note"><strong>Note:</strong> If you are running Eclipse and
encounter a warning about the VM debug port when opening DDMS, you can ignore it
if you're only interested in logs. However, if you want to further inspect and
control your processes from DDMS, then you should close Eclipse before launching DDMS so that
it may use the VM debugging port.</p>

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page.title=Android Application Framework FAQ
parent.title=FAQs, Tips, and How-to
parent.link=index.html
@jd:body
<ul>
<li><a href="#1">Do all the Activities and Services of an
application run in a single process?</a></li>
<li><a href="#2">Do all Activities run in the main thread of
an application process?</a></li>
<li><a href="#3">How do I pass complicated data structures
from one Activity/Service to another?</a></li>
<li><a href="#4">How can I check if an Activity is already
running before starting it?</a></li>
<li><a href="#5">If an Activity starts a remote service, is
there any way for the Service to pass a message back to the Activity?</a></li>
<li><a href="#6">How to avoid getting the Application not
responding dialog?</a></li>
<li><a href="#7">How does an application know if a package is
added or removed?</a></li>
</ul>
<a name="1" id="1"></a>
<h2>Do all the Activities and Services of an application run in a
single process?</h2>
<p>All Activities and Services in an application run in a single process by
default. If needed, you can declare an <code>android:process</code> attribute
in your manifest file, to explicitly place a component (Activity/Service) in
another process.</p>
<a name="2" id="2"></a>
<h2>Do all Activities run in the main thread of an application
process?</h2>
<p>By default, all of the application code in a single process runs
in the main UI thread. This is the same thread
that also handles UI events. The only exception is the code that handles
IPC calls coming in from other processes. The system maintains a
separate pool of transaction threads in each process to dispatch all
incoming IPC calls. The developer should create separate threads for any
long-running code, to avoid blocking the main UI thread.</p>
<a name="3" id="3"></a>
<h2>How do I pass data between Activities/Services within a single
application?</h2>
<p>It depends on the type of data that you want to share:</p>
<h3>Primitive Data Types</h3>
<p>To share primitive data between Activities/Services in an
application, use Intent.putExtras(). For passing primitive data that
needs to persist use the
<a href="{@docRoot}guide/topics/data/data-storage.html#preferences">
Preferences</a> storage mechanism.</p>
<h3>Non-Persistent Objects</h3>
<p>For sharing complex non-persistent user-defined objects for short
duration, the following approaches are recommended:
</p>
<h4>Singleton class</h4>
<p>You can take advantage of the fact that your application
components run in the same process through the use of a singleton.
This is a class that is designed to have only one instance. It
has a static method with a name such as <code>getInstance()</code>
that returns the instance; the first time this method is called,
it creates the global instance. Because all callers get the same
instance, they can use this as a point of interaction. For
example activity A may retrieve the instance and call setValue(3);
later activity B may retrieve the instance and call getValue() to
retrieve the last set value.</p>
<h4>A public static field/method</h4>
<p>An alternate way to make data accessible across Activities/Services is to use <em>public static</em>
fields and/or methods. You can access these static fields from any other
class in your application. To share an object, the activity which creates your object sets a
static field to point to this object and any other activity that wants to use
this object just accesses this static field.</p>
<h4>A HashMap of WeakReferences to Objects</h4>
<p>You can also use a HashMap of WeakReferences to Objects with Long
keys. When an activity wants to pass an object to another activity, it
simply puts the object in the map and sends the key (which is a unique
Long based on a counter or time stamp) to the recipient activity via
intent extras. The recipient activity retrieves the object using this
key.</p>
<h3>Persistent Objects</h3>
<p>Even while an application appears to continue running, the system
may choose to kill its process and restart it later. If you have data
that you need to persist from one activity invocation to the next, you
need to represent that data as state that gets saved by an activity when
it is informed that it might go away.</p>
<p>For sharing complex persistent user-defined objects, the
following approaches are recommended:
<ul>
<li>Application Preferences</li>
<li>Files</li>
<li>contentProviders</li>
<li>SQLite DB</li>
</ul>
</p>
<p>If the shared data needs to be retained across points where the application
process can be killed, then place that data in persistent storage like
Application Preferences, SQLite DB, Files or ContentProviders. Please refer to
the <a href="{@docRoot}guide/topics/data/data-storage.html">Data Storage</a>
for further details on how to use these components.</p>
<a name="4" id="4"></a>
<h2>How can I check if an Activity is already running before starting
it?</h2>
<p>The general mechanism to start a new activity if its not running&mdash;
or to bring the activity stack to the front if is already running in the
background&mdash; is the to use the NEW_TASK_LAUNCH flag in the startActivity()
call.</p>
<a name="5" id="5"></a>
<h2>If an Activity starts a remote service, is there any way for the
Service to pass a message back to the Activity?</h2>
<p>See the {@link android.app.Service} documentation's for examples of
how clients can interact with a service. You can take advantage of the
fact that your components run in the same process to greatly simplify
service interaction from the generic remote case, as shown by the "Local
Service Sample". In some cases techniques like singletons may also make sense.
<a name="6" id="6"></a>
<h2>How to avoid getting the Application not responding dialog?</h2>
<p>Please read the <a href="{@docRoot}guide/practices/design/responsiveness.html">Designing for Responsiveness</a>
document.</p>
<a name="7" id="7"></a>
<h2>How does an application know if a package is added or removed?
</h2>
<p>Whenever a package is added, an intent with PACKAGE_ADDED action
is broadcast by the system. Similarly when a package is removed, an
intent with PACKAGE_REMOVED action is broadcast. To receive these
intents, you should write something like this:
<pre>
&lt;receiver android:name ="com.android.samples.app.PackageReceiver"&gt;
&lt;intent-filter&gt;
&lt;action android:name="android.intent.action.PACKAGE_ADDED"/&gt;
&lt;action android:name="android.intent.action.PACKAGE_REMOVED"/&gt;
&lt;data android:scheme="package" /&gt;
&lt;/intent-filter&gt;
&lt;/receiver&gt;
</pre>
<br>
Here PackageReceiver is a BroadcastReceiver class.Its onReceive()
method is invoked, every time an application package is installed or
removed.
</p>

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page.title=Android FAQs
@jd:body
<dl>
<dt><a href="framework.html">Application Framework FAQ</a></dt>
<dd>Common questions about the Android Application Framework.</dd>
<dt><a href="licensingandoss.html">Open Source Licensing FAQ</a></dt>
<dd>Common topics around licensing and Android Open Source</dd>
<dt><a href="security.html">Android Security FAQ</a></dt>
<dd>Answers to common questions about Android security.</dd>
</dl>

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page.title=Android Open Source Licensing FAQ
parent.title=FAQs, Tips, and How-to
parent.link=index.html
@jd:body
<ul>
<li><a href="#mirror">Where can I find the open source components of Android?</a></li>
<li><a href="#timeline">When will we see more code released under open source licenses?</a></li>
<li><a href="#apache2">Why are you releasing the code under the Apache License instead of GPLv2?</a></li>
</ul>
<a name="mirror" id="mirror"></a><h2>Where can I find the open source components of Android?</h2>
<p>The source code for the full Android stack is available from the <a href="http://source.android.com">Android Open Source Project </a> site.
<p>Other mirrored GPL and LGPL'd components are available at <a href="http://code.google.com/p/android/downloads/list"><code>http://code.google.com/p/android/downloads/list</code></a>.</p>
<p>Notices for other licenses can be found within the SDK.</p>
<a name="apache2" id="apache2"></a><h2>Why are you releasing the code under the Apache License instead of GPLv2?</h2>
<p>One of the best explanations for the reasoning behind releasing code under Apache2 can be found in a <a href="http://arstechnica.com/news.ars/post/20071106-why-google-chose-the-apache-software-license-over-gplv2.html">ArsTechnica article</a> by Ryan Paul.</p>

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page.title=Android Security FAQ
parent.title=FAQs, Tips, and How-to
parent.link=index.html
@jd:body
<ul>
<li><a href="#secure">Is Android Secure?</a></li>
<li><a href="#issue">I think I found a security flaw. How do I report
it?</a></li>
<li><a href="#informed">How can I stay informed of Android security
announcements?</a></li>
<li><a href="#use">How do I securely use my Android phone?</a></li>
<li><a href="#malware">I think I found malicious software being distributed
for Android. How can I help?</a></li>
<li><a href="#fixes">How will Android-powered devices receive security fixes?</a>
</li>
<li><a href="#directfix">Can I get a fix directly from the Android Platform
Project?</a></li>
</ul>
<a name="secure" id="secure"></a><h2>Is Android secure?</h2>
<p>The security and privacy of our users' data is of primary importance to the
Android Open Source Project. We are dedicated to building and maintaining one
of the most secure mobile platforms available while still fulfilling our goal
of opening the mobile device space to innovation and competition.</p>
<p>The Android Platform provides a rich <a
href="http://code.google.com/android/devel/security.html">security model</a>
that allows developers to request the capabilities, or access, needed by their
application and to define new capabilities that other applications can request.
The Android user can choose to grant or deny an application's request for
certain capabilities on the handset.</p>
<p>We have made great efforts to secure the Android platform, but it is
inevitable that security bugs will be found in any system of this complexity.
Therefore, the Android team works hard to find new bugs internally and responds
quickly and professionally to vulnerability reports from external researchers.
</p>
<a name="issue" id="issue"></a><h2>I think I found a security flaw. How do I
report it?</h2>
<p>You can reach the Android security team at <a
href="mailto:security@android.com">security@android.com</a>. If you like, you
can protect your message using our <a
href="http://code.google.com/android/security_at_android_dot_com.txt">PGP
key</a>.</p>
<p>We appreciate researchers practicing responsible disclosure by emailing us
with a detailed summary of the issue and keeping the issue confidential while
users are at risk. In return, we will make sure to keep the researcher informed
of our progress in issuing a fix and will properly credit the reporter(s) when
we announce the patch. We will always move swiftly to mitigate or fix an
externally-reported flaw and will publicly announce the fix once patches are
available to users.</p>
<a name="informed" id="informed"></a><h2>How can I stay informed of Android
security announcements?</h2>
<p>An important part of sustainably securing a platform, such as, Android is
keeping the user and security community informed of bugs and fixes. We will
publicly announce security bugs when the fixes are available via postings to
the <a
href="http://groups.google.com/group/android-security-announce">android-security-announce</a>
group on Google Groups. You can subscribe to this group as you would a mailing
list and view the archives here.</p>
<p>For more general discussion of Android platform security, or how to use
security features in your Android application, please subscribe to <a
href="http://groups.google.com/group/android-security-discuss">android-security-discuss</a>.
</p>
<a name="use" id="use"></a><h2>How do I securely use my Android phone?</h2>
<p>As an open platform, Android allows users to load software from any
developer onto a device. As with a home PC, the user must be
aware of who is providing the software they are downloading and must decide
whether they want to grant the application the capabilities it requests.
This decision can be informed by the user's judgment of the software
developer's trustworthiness, and where the software came from.</p>
<p>Despite the security protections in Android, it is important
for users to only download and install software from developers they trust.
More details on how Android users can make smart security decisions will be
released when consumer devices become available.</p>
<a name="malware" id="malware"></a><h2>I think I found malicious software being
distributed for Android. How can I help?</h2>
<p>Like any other open platform, it will be possible for unethical developers
to create malicious software, known as <a
href="http://en.wikipedia.org/wiki/Malware">malware</a>, for Android. If you
think somebody is trying to spread malware, please let us know at <a
href="mailto:security@android.com">security@android.com</a>. Please include as
much detail about the application as possible, with the location it is
being distributed from and why you suspect it of being malicious software.</p>
<p>The term <i>malicious software</i> is subjective, and we cannot make an
exhaustive definition. Some examples of what the Android Security Team believes
to be malicious software is any application that:
<ul>
<li>drains the device's battery very quickly;</li>
<li>shows the user unsolicited messages (especially messages urging the
user to buy something);</li>
<li>resists (or attempts to resist) the user's effort to uninstall it;</li>
<li>attempts to automatically spread itself to other devices;</li>
<li>hides its files and/or processes;</li>
<li>discloses the user's private information to a third party, without the
user's knowledge and consent;</li>
<li>destroys the user's data (or the device itself) without the user's
knowledge and consent;</li>
<li>impersonates the user (such as by sending email or buying things from a
web store) without the user's knowledge and consent; or</li>
<li>otherwise degrades the user's experience with the device.</li>
</ul>
</p>
<a name="fixes" id="fixes"></a><h2>How will Android-powered devices receive security
fixes?</h2>
<p>The manufacturer of each device is responsible for distributing software
upgrades for it, including security fixes. Many devices will update themselves
automatically with software downloaded "over the air", while some devices
require the user to upgrade them manually.</p>
<p>When Android-powered devices are publicly available, this FAQ will provide links how
Open Handset Alliance members release updates.</p>
<a name="directfix" id="directfix"></a><h2>Can I get a fix directly from the
Android Platform Project?</h2>
<p>Android is a mobile platform that will be released as open source and
available for free use by anybody. This means that there will be many
Android-based products available to consumers, and most of them will be created
without the knowledge or participation of the Android Open Source Project. Like
the maintainers of other open source projects, we cannot build and release
patches for the entire ecosystem of products using Android. Instead, we will
work diligently to find and fix flaws as quickly as possible and to distribute
those fixes to the manufacturers of the products.</p>
<p>In addition, We will add security fixes to the open source distribution of
Android and publicly announce the changes on <a
href="http://groups.google.com/group/android-security-announce">android-security-announce</a>.
</p>
<p>If you are making an Android-powered device and would like to know how you can
properly support your customers by keeping abreast of software updates, please
contact us at <a
href="mailto:info@openhandsetalliance.com">info@openhandsetalliance.com</a>.</p>

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page.title=Troubleshooting
parent.title=FAQs, Tips, and How-to
parent.link=index.html
@jd:body
<p>Here are some tips and tricks for common Android errors. Don't forget to use the
ddms logcat capability to get a deeper view when errors occur. See <a href="{@docRoot}guide/developing/debug-tasks.html">Debugging</a> for more debugging tips. </p>
<ul>
<li><a href="#installeclipsecomponents">ADT Installation Error: "requires plug-in org.eclipse.wst.sse.ui".</a></li>
<li><a href="#nodevice">ADB reports &quot;no device&quot; when an emulator is running</a></li>
<li><a href="#noapp">My new application/activity isn't showing up in the device application
list </a></li>
<li><a href="#noupdate">I updated my app, but the updates don't seem to be showing up on
the device</a></li>
<li><a href="#layout_wilih">I'm getting a &quot;Binary XML file line #2: You must supply a layout_wilih
attribute&quot; error when I start an application</a></li>
<li><a href="#permission">My request to (<em>make a call, catch an incoming SMS, receive
a notification, send an intent to an Android application</em>) is being
ignored</a></li>
<li><a href="#build">Help! My project won't build in Eclipse</a></li>
<li><a href="#eclipse">Eclipse isn't talking to the emulator</a></li>
<li><a href="#majorminor">When I go to preferences in Eclipse and select "Android", I get the following error message: Unsupported major.minor version 49.0.</a></li>
<li><a href="#apidemosreinstall">I can't install ApiDemos apps in my IDE because of a signing error</a></li>
<li><a href="#gesturebuilderinstall">I can't install the GestureBuilder sample
app in the emulator</a></li>
<li><a href="#signingcalendar">I can't compile my app because the build tools generated an expired debug certificate</a></li>
<li><a href="#manifestfiles">Unable to view manifest files from within Eclipse</a></li>
</ul>
<a name="installeclipsecomponents" id="installeclipsecomponents"></a><h2>ADT Installation Error: "requires plug-in org.eclipse.wst.sse.ui".</h2>
<p>
The "Android Editors" feature of the ADT Plugin requires specific Eclipse components, such as WST. If you
encounter this error message during ADT installation, you need to install the
required Eclipse components and then try the ADT installation again. Follow the steps below to install the required components for the
Android Editors feature, based on the version of Eclipse that you are using.</p>
<table style="font-size:100%">
<tr><th>Eclipse 3.3 (Europa)</th><th>Eclipse 3.4 (Ganymede)</th></tr>
<tr>
<td width="50%">
<ol>
<li>From the dialog where you select the <strong>Update sites to visit</strong>, select the checkboxes for both the
ADT site, and the Callisto/Europa/Ganymede Discovery Site (you may want to
check <strong>Automatically select mirrors</strong> at the bottom).</li>
<li>Click <strong>Finish</strong>.</li>
<li>In the <strong>Next</strong> dialog, select the Android Plugins.</li>
<li>Now, expand the tree item of the discovery site. It seems that if you
don't do it, it doesn't load the content of the discovery site.</li>
<li>On the right, click <strong>Select required</strong>. This will select all the components
that are required to install the Android plugin (wst, emf, etc...).</li>
<li>Click <strong>Next</strong>, accept the agreement, click <strong>Install All</strong>, and restart Eclipse.</li>
</ol>
</td>
<td>
<ol>
<li>Select <strong>Help</strong> &gt; <strong>Software Updates...</strong></li>
<li>Select the <strong>Installed Software</strong> tab.</li>
<li>Click <strong>Update...</strong></li>
<li>If an update for ADT is available, select it and click <strong>Finish</strong>.</li>
</ol>
</td>
</tr>
</table>
</p>
<a name="nodevice"></a><h2>ADB reports &quot;no device&quot; when an emulator is running</h2>
<p>Try restarting adb by stopping it (<code>adb
kill-server</code>) then any other adb command to restart it.</p>
<a name="noapp"></a><h2>My new application/activity isn't showing up in the
applications list </h2>
<ul>
<li>You often must restart your device or emulator before a new activity shows
up in the applications list. This is particularly true when it is a completely
new application with a new AndroidManifest.xml file.</li>
<li>If this is for a new activity in an existing AndroidManifest.xml file, did
you include an <code>&lt;activity&gt;</code> tag for your app (or a <code>&lt;service&gt;</code> tag
for a service, or a <code>&lt;receiver&gt;</code> tag for a receiver, etc.)? </li>
<li>Make sure that your AndroidManifest.xml file is valid. Errors in attribute
values, such as the <em>value </em> attribute in <code>&lt;action <em>value</em>=&quot;<em>&lt;something&gt;</em>&quot;&gt;</code>
will often not be caught by compilers, but will prevent your application
from being displayed because the intent filter will not be matched. Extra
spaces or other characters can often sneak into these strings.</li>
<li>Did you send your .apk file to the device (<a href="{@docRoot}guide/developing/tools/adb.html#move">adb install</a>)?</li>
<li>Run logcat on your device (<code>adb logcat</code>)
and then install your .apk file. Check the logcat output to see whether the
application is being installed and recognized properly. Here's sample output
from a successful installation:
<pre>I/FileObserver( 414): *** onEvent wfd: 3 mask: 8 path: MyRSSReader.apk
D/PackageManager( 414): Scanning package: /data/app/MyRSSReader.apk
D/PackageManager( 414): Adding package com.example.codelab.rssexample
D/PackageManager( 414): Registered content provider: my_rss_item, className = com.example.codelab.rssexample.RssContentProvider, isSyncable = false
D/PackageManager( 414): Providers: com.example.codelab.rssexample.RssContentProvider
D/PackageManager( 414): Activities: com.example.codelab.rssexample.MyRssReader com.example.codelab.rssexample.MyRssReader2 </pre>
</li>
<li>If logcat shows that the package manager is having problems loading the manifest
file, force your manifest to be recompiled by adding a space in the file and
compiling it.</li>
</ul>
<a name="noupdate"></a><h2>I updated my app, but the updates don't seem to be showing up on the device</h2>
<p>Did you remember to send your .apk file to the device (<a href="{@docRoot}guide/developing/tools/adb.html#move">adb
install</a>)?</p>
<a name="layout_wilih"></a><h2>I'm getting a &quot;Binary XML file line #2: You must supply a layout_wilih
attribute&quot; error
when I start an application (but I declare a layout_wilih attribute <em>right
there!!!</em>)</h2>
<ul>
<li>Make sure that the SDK you are building with is the same version as the Android
OS that you are running on. </li>
<li>Make sure that you're calling setContentView() early in your onCreate() method.
Calling other methods, such as setListAdapter() before calling setContentView()
can sometimes create odd errors when Android tries to access screen elements
that haven't been set before.</li>
</ul>
<a name="permission"></a><h2>My request to (<em>make a call, catch an incoming SMS,
receive a notification, send an intent to an Android application</em>) is being
ignored</h2>
<p>You might not have permission (or might not have requested permission) to
call this activity or receive this intent. Many standard Android activities,
such as making a call, have a permission assigned to it to prevent arbitrary
applications from sending or receiving requests. See <a
href="{@docRoot}guide/topics/security/security.html">Security and
Permissions</a> for more information on permissions, and
{@link android.Manifest.permission Manifest.permission} for a list of
standard permissions supported by the Android platform.
</p>
<a name="build"></a><h2>Help! My project won't build in Eclipse</h2>
<p>If your project doesn't build, you may notice symptoms such as new
resources added in the <code>res/</code> sub-folders not showing up in the R class,
the emulator not being started, not being able to run the application, or even seeming to run an old version of the application.</p>
<p>To troubleshoot these types of problems, first try:</p>
<ol>
<li>Switch to the DDMS view in Eclipse (if you don't already have it open):
<ol type="a">
<li>From the menu select <code>Window &gt; Open Perspective &gt; Other</code></li>
<li>Select DDMS from the list and hit OK</li>
</ol>
</li>
<li>In the Devices panel (top right panel by default), click on the down triangle
to bring up the panel menu</li>
<li>Select <code>Reset ADB</code> from the menu, and then try running the
application again</li>
</ol>
<p>If the above still doesn't work, you can try these steps:</p>
<ol>
<li>
Check the console and problems tabs at the bottom of the Eclipse UI
</li>
<li>
If there are problems listed in either place, they should give you a clue
what is wrong
</li>
<li>
If you aren't sure if the problems are fresh or stale, clear the console
with a right click &gt; Clear, then clean the project
</li>
<li>
To clean the project (a good idea with any kind of build error), select
Project &gt; Clean from the eclipse main menu, then select the project you
are working on (or clean all)
</li>
</ol>
<a name="eclipse"></a><h2>Eclipse isn't talking to the emulator</h2>
<p>When communication doesn't seem to be happening between Eclipse and the emulator, symptoms can include: nothing happening when you press run, the emulator hanging waiting
for a debugger to connect, or errors that Eclipse reports about not being able
to find the emulator or shell. By far the most common symptom is that when you press run, the emulator starts (or
is already running), but the application doesn't start.</p>
<p>
You may find any of these steps will fix the problem and with practice you
probably can figure out which one you need to do for your particular issue, but
to start with, the safest option is to run through all of them in order:</p>
<ol>
<li>
Quit the emulator if it is running
</li>
<li>
Check that any emulator processes are killed (sometimes they can hang, use ps on unix or mac, or task manager in the process view on
windows).
</li>
<li>
Quit Eclipse
</li>
<li>
From the command line, type:
<pre>adb kill-server </pre>
</li>
<li>
Start Eclipse and try again
</li>
</ol>
<a name="majorminor"></a><h2>When I go to preferences in Eclipse and select "Android", I get the following error message: Unsupported major.minor version 49.0.</h2>
<p>This error is displayed if you are using an older version of the JDK. Please make sure you are using JDK version 5 or 6.</p>
<h2 id="apidemosreinstall">I can't install ApiDemos apps in my IDE because of a signing error</a></h2>
<p>The Android system requires that all applications be signed, as described in
<a href="{@docRoot}guide/publishing/app-signing.html">Signing Your Applications</a>. The ApiDemos
applications included with the SDK are preinstalled on the emulator and for that reason have been
compiled and signed with a private key.</p>
If you want to modify or run one of the ApiDemos apps from Eclipse/ADT or other IDE, you can do so
so only after you uninstall the <em>preinstalled</em> version of the app from the emulator. If
you try to run an ApiDemos apps from your IDE without removing the preinstalled version first,
you will get errors similar to: </p>
<pre>[2008-08-13 15:14:15 - ApiDemos] Re-installation failed due to different application signatures.
[2008-08-13 15:14:15 - ApiDemos] You must perform a full uninstall of the application. WARNING: ...This will remove the application data!
[2008-08-13 15:14:15 - ApiDemos] Please execute 'adb uninstall com.android.samples' in a shell.</pre>
<p>The error occurs because, in this case, you are attempting to install another copy of ApiDemos
onto the emulator, a copy that is signed with a different certificate (the Android IDE tools will
have signed the app with a debug certificate, where the existing version was already signed with
a private certificate). The system does not allow this type of reinstallation. </p>
<p>To resolve the issue, you need to fully uninstall the preinstalled and then reinstall it using
the adb tool. Here's how to do that:</p>
<ol>
<li>In a terminal, change to the tools directory of the SDK.</li>
<li>If no emulator instance is running, start an emulator using using the command <code>emulator &</code>.</li>
<li>Uninstall the preinstalled app using the command <code>adb uninstall com.android.samples</code>.</li>
<li>Reinstall the app using the command <code>adb install &lt;path to the ApiDemos.apk&gt;</code>. If you are
working in Eclipse/ADT, you can just compile and run the app in the normal way. </li>
</ol>
<p>Note that if multiple emulator instances are running, you need to direct your uninstall/install
commands to the emulator instance that you are targeting. To do that you can add the
<code>-s &lt;serialNumber&gt;</code> to the command, for example: </p>
<pre>adb -s emulator-5556 install</pre>
<p>For more information about adb, see the <a href="{@docRoot}guide/developing/tools/adb.html">Android Debug Bridge</a>
documentation.</p>
<h2 id="gesturebuilderinstall">I can't install the GestureBuilder sample
app in the emulator</a></h2>
<p>This is similar to the ApiDemos problem described above, except that
you cannot fix it by uninstalling GestureBuilder from the emulator. The
GestureBuilder app cannot be uninstalled because it is currently installed
within the system files themselves.</p>
<p><strong>Symptoms</strong></p>
<ul><li><p>You cannot run GestureBuilder in the emulator:</p>
<pre>[2009-12-10 14:57:19 - GestureBuilderActivity]Re-installation failed due to different application signatures.
[2009-12-10 14:57:19 - GestureBuilderActivity]You must perform a full uninstall of the application. WARNING: This will remove the application data!
[2009-12-10 14:57:19 - GestureBuilderActivity]Please execute 'adb uninstall com.android.gesture.builder' in a shell.</pre>
</li>
<li><p>Running <code>adb uninstall com.android.gesture.builder</code> fails:</p>
<pre>$ adb uninstall com.android.gesture.builder
Failure</pre>
</li></ul>
<p>For now, the work-around is to change the sample's package name
so that the system can install it as a new app rather than as a
replacement for the existing GestureBuilder app. To change the
package name, open the manifest file and modify the package attribute
of the manifest element. Next, update imports and other references to
the package name, rebuild the app, and run it in an AVD.</p>
<p>For example, here's how you could do this in Eclipse:</p>
<ol>
<li>Right-click on the package name
(<code>src/com.android.gesture.builder</code>).</li>
<li>Select <strong>Refactor &gt; Rename</strong> and change the name, for example to
<code>com.android.gestureNEW.builder</code>. </li>
<li>Open the manifest file. Inside the <code>&lt;manifest&gt;</code>
tag, change the package name to
<code>com.android.gestureNEW.builder</code>.</li>
<li>Open each of the two Activity files and do Ctrl-Shift-O to add
missing import packages, then save each file.</li>
<li>Run the GestureBuilder application on the emulator.</li>
</ol>
<p>If you get an error message such as "Could not load /sdcard/gestures.
Make sure you have a mounted SD card," be sure that your target AVD has an
SD card. To create an AVD that has an SD card, use the
<a href="{@docRoot}guide/developing/tools/avd.html#options"><code>-c</code>
option</a> in the <code>android create avd</code> command.</p>
<h2 id="signingcalendar">I can't compile my app because the build tools generated an expired debug certificate</h2>
<p>If your development machine uses a locale that has a non-Gregorian calendar, you may encounter problems when first trying to compile and run your application. Specifically, you may find that the Android build tools won't compile your application because the debug key is expired. </p>
<p>The problem occurs because the Keytool utility &mdash; included in the JDK and used by the Android build tools &mdash; fails to properly handle non-Gregorian locales and may create validity dates that are in the past. That is, it may generate a debug key that is already expired, which results in the compile error.</p>
<p>If you encounter this problem, follow these steps to work around it: </p>
<ol>
<li>First, delete the debug keystore/key already generated by the Android build tools. Specifically, delete the <code>debug.keystore</code> file. On Linux/Mac OSX, the file is stored in <code>~/.android</code>. On Windows XP, the file is stored in <code>
C:\Documents and Settings\&lt;user&gt;\.android</code>. On Windows Vista, the file is stored in <code>
C:\Users\&lt;user&gt;\.android</code></li>
<li>Next, you can either
<ul>
<li>Temporarily change your development machine's locale (date and time) to one that uses a Gregorian calendar, for example, United States. Once the locale is changed, use the Android build tools to compile and install your app. The build tools will regenerate a new keystore and debug key with valid dates. Once the new debug key is generated, you can reset your development machine to the original locale. </li>
<li>Alternatively, if you do not want to change your machine's locale settings, you can generate the keystore/key on any machine using the Gregorian calendar, then copy the <code>debug.keystore</code> file from that computer to the proper location on your development machine. </li>
</ul>
</li>
</ol>
<p>This problem has been verified on Windows and may apply to other platforms. </p>
<p>For general information about signing Android applications, see
<a href="{@docRoot}guide/publishing/app-signing.html">Signing Your Applications</a>. </p>
<h2 id="manifestfiles">Unable to view manifest files from within
Eclipse</a></h2>
<p>When you try to open an application's manifest file from within
Eclipse, you might get an error such as this one:</p>
<pre>An error has occurred. See error log for more details.
org.eclipse.wst.sse.ui.StructuredTextEditor.isBlockSelectionModeEnabled()Z</pre>
<p>Try reverting to the 3.0 version of the Eclipse XML Editors and
Tools. If this does not work, remove the 3.1 version of the tool. To do
this in Eclipse 3.4:</p>
<ol>
<li>Select <strong>Help > Software Updates...</strong></li>
<li>Select the <strong>Installed Software</strong> tab.</li>
<li>Select <strong>Eclipse XML Editors and Tools</strong>.</li>
<li>Click <strong>Uninstall</strong>.</li>
<li>Click <strong>Finish</strong>.</li>
</ol>
<p>When you restart Eclipse, you should be able to view the manifest
files. </p>