M7350/base/docs/html/guide/topics/ui/notifiers/toasts.jd

page.title=Creating Toast Notifications
parent.title=Notifying the User
parent.link=index.html
@jd:body

<div id="qv-wrapper">
  <div id="qv">
    <h2>Quickview</h2>
    <ol>
      <li>A toast is a message that appears on the surface of the screen for a moment, but it
does not take focus (or pause the current activity), so it cannot accept user input</li>
      <li>You can customize the toast layout to include images</li>
    </ol>
    
    <h2>In this document</h2>
    <ol>
      <li><a href="#Basics">The Basics</a></li>
      <li><a href="#Positioning">Positioning your Toast</a></li>
      <li><a href="#CustomToastView">Creating a Custom Toast View</a></li>
    </ol>
    
    <h2>Key classes</h2>
    <ol>
      <li>{@link android.widget.Toast}</li>
    </ol>
  </div>
</div>

<p>A toast notification is a message that pops up on the surface of the window.
It only fills the amount of space required for the message and the user's current
activity remains visible and interactive. The notification automatically fades in and 
out, and does not accept interaction events.</p>

<p>The screenshot below shows an example toast notification from the Alarm application.
Once an alarm is turned on, a toast is displayed to assure you that the 
alarm was set.</p>
<img src="{@docRoot}images/toast.png" alt="" />

<p>A toast can be created and displayed from an {@link android.app.Activity} or 
{@link android.app.Service}. If you create a toast notification from a Service, it
appears in front of the Activity currently in focus.</p>

<p>If user response to the notification is required, consider using a 
<a href="notifications.html">Status Bar Notification</a>.</p>


<h2 id="Basics">The Basics</h2>

<p>First, instantiate a {@link android.widget.Toast}
object with one of the {@link android.widget.Toast#makeText(Context,int,int) makeText()} methods.
This method takes three parameters: the application {@link android.content.Context},
the text message, and the duration for the toast. It returns a properly initialized Toast
object. You can display the toast notification with {@link android.widget.Toast#show()},
as shown in the following example:</p>

<pre>
Context context = getApplicationContext();
CharSequence text = "Hello toast!";
int duration = Toast.LENGTH_SHORT;

Toast toast = Toast.makeText(context, text, duration);
toast.show();
</pre>

<p>This example demonstrates everything you need for most toast notifications.
You should rarely need anything else. You may, however, want to position the 
toast differently or even use your own layout instead of a simple text message. 
The following sections describe how you can do these things.</p>

<p>You can also chain your methods and avoid holding on to the Toast object, like this:</p>
<pre>Toast.makeText(context, text, duration).show();</pre>


<h2 id="Positioning">Positioning your Toast</h2>

<p>A standard toast notification appears near the bottom of the screen, centered horizontally.
You can change this position with the {@link android.widget.Toast#setGravity(int,int,int)}
method. This accepts three parameters: a {@link android.view.Gravity} constant, 
an x-position offset, and a y-position offset.</p>

<p>For example, if you decide that the toast should appear in the top-left corner, you can set the
gravity like this:</p>
<pre>
toast.setGravity(Gravity.TOP|Gravity.LEFT, 0, 0);
</pre>

<p>If you want to nudge the position to the right, increase the value of the second parameter. 
To nudge it down, increase the value of the last parameter.


<h2 id="CustomToastView">Creating a Custom Toast View</h2>

<img src="{@docRoot}images/custom_toast.png" alt="" style="float:right" />

<p>If a simple text message isn't enough, you can create a customized layout for your
toast notification. To create a custom layout, define a View layout,
in XML or in your application code, and pass the root {@link android.view.View} object
to the {@link android.widget.Toast#setView(View)} method.</p>

<p>For example, you can create the layout for the toast visible in the screenshot to the right
with the following XML (saved as <em>toast_layout.xml</em>):</p>
<pre>
&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:id="@+id/toast_layout_root"
              android:orientation="horizontal"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:padding="10dp"
              android:background="#DAAA"
              >
    &lt;ImageView android:id="@+id/image"
               android:layout_width="wrap_content"
               android:layout_height="fill_parent"
               android:layout_marginRight="10dp"
               />
    &lt;TextView android:id="@+id/text"
              android:layout_width="wrap_content"
              android:layout_height="fill_parent"
              android:textColor="#FFF"
              />
&lt;/LinearLayout>
</pre> 

<p>Notice that the ID of the LinearLayout element is "toast_layout". You must use this
ID to inflate the layout from the XML, as shown here:</p>

<pre>
LayoutInflater inflater = getLayoutInflater();
View layout = inflater.inflate(R.layout.toast_layout,
                               (ViewGroup) findViewById(R.id.toast_layout_root));

ImageView image = (ImageView) layout.findViewById(R.id.image);
image.setImageResource(R.drawable.android);
TextView text = (TextView) layout.findViewById(R.id.text);
text.setText("Hello! This is a custom toast!");

Toast toast = new Toast(getApplicationContext());
toast.setGravity(Gravity.CENTER_VERTICAL, 0, 0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(layout);
toast.show();
</pre>

<p>First, retrieve the {@link android.view.LayoutInflater} with 
{@link android.app.Activity#getLayoutInflater()} 
(or {@link android.content.Context#getSystemService(String) getSystemService()}),
and then inflate the layout from XML using 
{@link android.view.LayoutInflater#inflate(int, ViewGroup)}. The first parameter
is the layout resource ID and the second is the root View. You can use
this inflated layout to find more View objects in the layout, so now capture and 
define the content for the ImageView and TextView elements. Finally, create
a new Toast with {@link android.widget.Toast#Toast(Context)} and set some properties
of the toast, such as the gravity and duration. Then call
{@link android.widget.Toast#setView(View)} and pass it the inflated layout.
You can now display the toast with your custom layout by calling 
{@link android.widget.Toast#show()}.</p>

<p class="note"><strong>Note:</strong> Do not use the public constructor for a Toast 
unless you are going to define the layout with {@link android.widget.Toast#setView(View)}.
If you do not have a custom layout to use, you must use
{@link android.widget.Toast#makeText(Context,int,int)} to create the Toast.</p>