docs/html/guide/topics/ui/notifiers/notifications.jd

page.title=Status Bar Notifications
parent.title=Notifications
parent.link=index.html
@jd:body

<div id="qv-wrapper">
  <div id="qv">
    <h2>Quickview</h2>
    <ul>
      <li>A status bar notification allows your application to notify the user of an event
without interupting their current activity</li>
      <li>You can attach an intent to your notification that the system will initiate when the
user clicks it</li>
    </ul>

    <h2>In this document</h2>
    <ol>
      <li><a href="#Basics">The Basics</a></li>
      <li><a href="#ManageYourNotifications">Managing your Notifications</a></li>
      <li><a href="#CreateANotification">Creating a Notification</a>
        <ol>
          <li><a href="#Updating">Updating the notification</a></li>
          <li><a href="#Sound">Adding a sound</a></li>
          <li><a href="#Vibration">Adding vibration</a></li>
          <li><a href="#Lights">Adding flashing lights</a></li>
          <li><a href="#More">More features</a></li>
        </ol>
      </li>
      <li><a href="#CustomExpandedView">Creating a Custom Notification Layout</a></li>
    </ol>
    <h2>Key classes</h2>
    <ol>
      <li>{@link android.app.Notification}</li>
      <li>{@link android.app.NotificationManager}</li>
    </ol>
  </div>
</div>

<p>A status bar notification adds an icon to the system's status bar
(with an optional ticker-text message) and a notification message in the notifications window.
When the user selects the notification, Android fires an
{@link android.content.Intent} that is defined by the {@link android.app.Notification} (usually to
launch an {@link android.app.Activity}).
You can also configure the notification to alert the user with a sound, a vibration, and flashing
lights on the device.</p>

<p>A status bar notification should be used for any case in
which a background service needs to alert the user about an event that requires a response. A
background service
<strong>should never</strong> launch an activity on its own in order to receive user interaction.
The service should instead create a status bar notification that will launch the activity
when selected by the user.</p>

<p>Figure 1 shows the status bar with a notification icon on the left side.</p>
<img src="{@docRoot}images/status_bar.png" alt="" />
<p class="img-caption"><strong>Figure 1.</strong> Status bar with a notification.</p>

<p>Figure 2 shows the notification's message in the notifications window.</p>

<img src="{@docRoot}images/notifications_window.png" alt="" />
<p class="img-caption"><strong>Figure 2.</strong> The notifications window.</p>


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

<p>An {@link android.app.Activity} or {@link android.app.Service} can initiate a status bar
notification. Because an activity can perform actions only while it is
running in the foreground and its window has focus, you will usually create status bar notifications
from a
service. This way, the notification can be created from the background,
while the user is using another application or
while the device is asleep. To create a notification, you must use two
classes: {@link android.app.Notification} and {@link android.app.NotificationManager}.</p>

<p>Use an instance of the {@link android.app.Notification} class to define the properties of your
status bar notification, such as the status bar icon, the notification message, and extra settings
such as a sound to play. The {@link android.app.NotificationManager} is an Android system service
that executes and manages all status bar notifications. You do not instantiate the
{@link android.app.NotificationManager} directly. In order
to give it your {@link android.app.Notification}, you must retrieve a reference to the
{@link android.app.NotificationManager} with
{@link android.app.Activity#getSystemService(String) getSystemService()} and
then, when you want to notify the user, pass it your {@link android.app.Notification} with
{@link android.app.NotificationManager#notify(int,Notification) notify()}. </p>

<p>To create a status bar notification:</p>
<ol>
  <li>Get a reference to the {@link android.app.NotificationManager}:
<pre>
String ns = Context.NOTIFICATION_SERVICE;
NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);
</pre>
  </li>
  <!-- use Notification.Builder in 3.0 -->
  <li>Instantiate the {@link android.app.Notification}:
<pre>
int icon = R.drawable.notification_icon;
CharSequence tickerText = "Hello";
long when = System.currentTimeMillis();

Notification notification = new Notification(icon, tickerText, when);
</pre>
  </li>
  <li>Define the notification's message and {@link android.app.PendingIntent}:
<pre>
Context context = getApplicationContext();
CharSequence contentTitle = "My notification";
CharSequence contentText = "Hello World!";
Intent notificationIntent = new Intent(this, MyClass.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);

notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
</pre>
  </li>
  <li>Pass the {@link android.app.Notification} to the {@link android.app.NotificationManager}:
<pre>
private static final int HELLO_ID = 1;

mNotificationManager.notify(HELLO_ID, notification);
</pre>
  <p>That's it. Your user has now been notified.</p>
  </li>
</ol>


<h2 id="ManageYourNotifications">Managing your Notifications</h2>

<p>The {@link android.app.NotificationManager} is a system service that manages all
notifications. You must retrieve a reference to it with the
{@link android.app.Activity#getSystemService(String) getSystemService()} method.
For example:</p>
<pre>
String ns = Context.NOTIFICATION_SERVICE;
NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);
</pre>

<p>When you want to deliver your status bar notification, pass the {@link android.app.Notification}
to the {@link android.app.NotificationManager} with {@link
android.app.NotificationManager#notify(int,Notification)}.
The first parameter is the unique ID for the notification and the second is the {@link
android.app.Notification} object.
The ID uniquely identifies the notification from within your
application. The ID is necessary if you need to update the notification or (if
your application manages different kinds of notifications) select the appropriate action
when the user returns to your application via the intent defined in the notification.</p>

<p>To clear the status bar notification when the user selects it from the notifications
window, add the "FLAG_AUTO_CANCEL" flag to your {@link android.app.Notification}. You can
also clear it manually with {@link android.app.NotificationManager#cancel(int)}, passing it the
notification ID, or clear all your notifications with {@link
android.app.NotificationManager#cancelAll()}.</p>


<h2 id="CreateANotification">Creating a Notification</h2>

<p>A {@link android.app.Notification} object defines the details of the notification
message that is displayed in the status bar and notifications window, and any other
alert settings, such as sounds and blinking lights.</p>

<p>A status bar notification <em>requires</em> all of the following:</p>
<ul>
  <li>An icon for the status bar</li>
  <li>A title and message, unless you define a
    <a href="#CustomExpandedView">custom notification layout</a></li>
  <li>A {@link android.app.PendingIntent}, to be fired when the notification is selected</li>
</ul>
<p>Optional settings for the status bar notification include:</p>
<ul>
  <li>A ticker-text message for the status bar</li>
  <li>An alert sound</li>
  <li>A vibrate setting</li>
  <li>A flashing LED setting</li>
</ul>

<p>The starter-kit for a new notification includes the
{@link android.app.Notification#Notification(int,CharSequence,long)} constructor and the
{@link android.app.Notification#setLatestEventInfo(Context,CharSequence,CharSequence,PendingIntent)}
method. These define all the required settings for a notification.
The following snippet demonstrates a basic notification setup:</p>
<pre>
int icon = R.drawable.notification_icon;        // icon from resources
CharSequence tickerText = "Hello";              // ticker-text
long when = System.currentTimeMillis();         // notification time
Context context = getApplicationContext();      // application Context
CharSequence contentTitle = "My notification";  // message title
CharSequence contentText = "Hello World!";      // message text

Intent notificationIntent = new Intent(this, MyClass.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);

// the next two lines initialize the Notification, using the configurations above
Notification notification = new Notification(icon, tickerText, when);
notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
</pre>


<h3 id="Updating">Updating the notification</h3>

<p>You can update the information in your status bar notification as events
continue to occur in your application. For example, when a new SMS text message arrives
before previous messages have been read, the Messaging application updates the existing
notification to display the total number of new messages received.
This practice of updating an existing notification is much better than adding new
notifications, because it avoids clutter in the notifications window.</p>

<p>Because each notification is uniquely identified
by the {@link android.app.NotificationManager} with an integer ID, you can revise the notification
by calling {@link
android.app.Notification#setLatestEventInfo(Context,CharSequence,CharSequence,PendingIntent)
setLatestEventInfo()} with new values, change some field values of the notification, and then call
{@link android.app.NotificationManager#notify(int,Notification) notify()} again.</p>

<p>You can revise each property with the object member fields
(except for the {@link android.content.Context} and the notification title and text). You
should always revise the text message when you update the notification by calling
{@link android.app.Notification#setLatestEventInfo(Context,CharSequence,CharSequence,PendingIntent)
setLatestEventInfo()} with new values for <var>contentTitle</var> and <var>contentText</var>.
Then call {@link android.app.NotificationManager#notify(int,Notification) notify()} to update the
notification. (Of course, if you've created a <a href="#CustomExpandedView">custom notification
layout</a>, then updating these title and text values has no effect.)</p>


<h3 id="Sound">Adding a sound</h3>

<p>You can alert the user with the default notification sound
(which is defined by the user) or with a sound specified by your application.</p>

<p>To use the user's default sound, add "DEFAULT_SOUND" to the <var>defaults</var> field:</p>
<pre>
notification.defaults |= Notification.DEFAULT_SOUND;
</pre>

<p>To use a different sound with your notifications, pass a Uri reference to the
<var>sound</var> field.
The following example uses a known audio file saved to the device SD card:</p>
<pre>
notification.sound = Uri.parse("file:///sdcard/notification/ringer.mp3");
</pre>

<p>In the next example, the audio file is chosen from the internal
{@link android.provider.MediaStore.Audio.Media MediaStore}'s {@link android.content.ContentProvider}:</p>
<pre>
notification.sound = Uri.withAppendedPath(Audio.Media.INTERNAL_CONTENT_URI, "6");
</pre>

<p>In this case, the exact ID of the media file ("6") is known and appended to the content
{@link android.net.Uri}. If you don't know the exact ID, you must query all the
media available in the {@link android.provider.MediaStore} with a {@link
android.content.ContentResolver}.
See the <a href="{@docRoot}guide/topics/providers/content-providers.html">Content Providers</a>
documentation for more information on using a ContentResolver.</p>

<p>If you want the sound to continuously repeat until the user responds to the notification
or the notification is cancelled, add {@link android.app.Notification#FLAG_INSISTENT} to the
<var>flags</var> field.</p>

<p class="note"><strong>Note:</strong> If the <var>defaults</var> field includes
{@link android.app.Notification#DEFAULT_SOUND}, then the default sound overrides any sound defined
by the <var>sound</var> field.</p>


<h3 id="Vibration">Adding vibration</h3>

<p>You can alert the user with the the default
vibration pattern or with a vibration pattern defined by your application.</p>

<p>To use the default pattern, add {@link android.app.Notification#DEFAULT_VIBRATE} to the
<var>defaults</var> field:</p>
<pre>
notification.defaults |= Notification.DEFAULT_VIBRATE;
</pre>

<p>To define your own vibration pattern, pass an array of <em>long</em> values to the
<var>vibrate</var> field:</p>
<pre>
long[] vibrate = {0,100,200,300};
notification.vibrate = vibrate;
</pre>

<p>The long array defines the alternating pattern for the length of vibration off and on
(in milliseconds). The first value is how long to wait (off) before beginning, the second
value is the length of the first vibration, the third is the next length off, and so on.
The pattern can be as long as you like, but it can't be set to repeat.
</p>

<p class="note"><strong>Note:</strong> If the <var>defaults</var> field includes
{@link android.app.Notification#DEFAULT_VIBRATE}, then the default vibration overrides any vibration
defined by the
<var>vibrate</var> field.</p>


<h3 id="Lights">Adding flashing lights</h3>

<p>To alert the user by flashing LED lights, you can implement the default
light pattern (if available), or define your own color and pattern for the lights.</p>

<p>To use the default light setting, add {@link android.app.Notification#DEFAULT_LIGHTS} to the
<var>defaults</var> field:</p>
<pre>
notification.defaults |= Notification.DEFAULT_LIGHTS;
</pre>

<p>To define your own color and pattern, define a value for the <var>ledARGB</var> field
(for the color), the <var>ledOffMS</var> field (length of time, in milliseconds, to
keep the light off), the <var>ledOnMS</var> (length of time, in milliseconds, to keep the light on),
and also add {@link android.app.Notification#FLAG_SHOW_LIGHTS} to the <var>flags</var> field:</p>
<pre>
notification.ledARGB = 0xff00ff00;
notification.ledOnMS = 300;
notification.ledOffMS = 1000;
notification.flags |= Notification.FLAG_SHOW_LIGHTS;
</pre>

<p>In this example, the green light repeatedly flashes on for 300 milliseconds and
turns off for one second. Not every color in the spectrum is supported by the
device LEDs, and not every device supports the same colors, so the hardware
estimates to the best of its ability. Green is the most common notification color.</p>


<h3 id="More">More features</h3>

<p>You can add several more features to your notifications
using {@link android.app.Notification} fields and flags. Some useful features include the
following:</p>

<dl>
  <dt>{@link android.app.Notification#FLAG_AUTO_CANCEL} flag</dt>
  <dd>Add this to the <var>flags</var> field to automatically cancel the notification
  after it is selected from the notifications window.</dd>
  <dt>{@link android.app.Notification#FLAG_INSISTENT} flag</dt>
  <dd>Add this to the <var>flags</var> field to repeat the audio until the
  user responds.</dd>
  <dt>{@link android.app.Notification#FLAG_ONGOING_EVENT} flag</dt>
  <dd>Add this to the <var>flags</var> field to group the notification under the "Ongoing"
  title in the notifications window. This indicates that the application is on-going &mdash;
  its processes are still running in the background, even when the application is not
  visible (such as with music or a phone call).</dd>
  <dt>{@link android.app.Notification#FLAG_NO_CLEAR} flag</dt>
  <dd>Add this to the <var>flags</var> field to indicate that the notification should
  <em>not</em> be cleared by the "Clear notifications" button. This is particularly useful if
  your notification is on-going.</dd>
  <dt>{@link android.app.Notification#number} field</dt>
  <dd>This value indicates the current number of events represented by the notification.
  The appropriate number is overlaid on top of the status bar icon.
  If you intend to use this field, then you must start with "1" when the Notification is first
  created. (If you change the value from zero to anything greater during an update, the number
  is not shown.)</dd>
  <dt>{@link android.app.Notification#iconLevel} field</dt>
  <dd>This value indicates the current level of a
  {@link android.graphics.drawable.LevelListDrawable} that is used for the notification icon.
  You can animate the icon in the status bar by changing this value to correlate with the
  drawable's defined in a LevelListDrawable. See the {@link android.graphics.drawable.LevelListDrawable}
  reference for more information.</dd>
</dl>

<p>See the {@link android.app.Notification} class reference for more information about additional
features that you can customize for your application.</p>


<h2 id="CustomExpandedView">Creating a Custom Notification Layout</h2>

<div class="figure" style="width:200px;margin-top:0">
<img src="{@docRoot}images/custom_message.png" alt="" />
<p class="img-caption"><strong>Figure 3.</strong> Notification with a custom layout.</p>
</div>

<p>By default, the notification that appears in the notifications window includes a title
and the message text.
These are defined by the <var>contentTitle</var> and <var>contentText</var>
parameters of the {@link android.app.Notification#setLatestEventInfo(Context,CharSequence,CharSequence,PendingIntent)
setLatestEventInfo()} method. However, you can also define a custom layout for the
notification using
{@link android.widget.RemoteViews}. Figure 3 shows an example of a
custom notification layout. It looks similar to the default notification, but is
actually created with a custom XML layout.</p>

<p>To define your own layout for the notification,
instantiate a {@link android.widget.RemoteViews} object that inflates a custom layout file, then
pass the {@link android.widget.RemoteViews} to the <var>contentView</var> field of your
Notification.</p>

<p>Creating a custom notification layout is best understood with an example:</p>

<ol>
  <li>Create the XML layout for the notification.
    For example, the following layout is called <code>custom_notification.xml</code>:
<pre>
&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dp" >
    &lt;ImageView android:id="@+id/image"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_alignParentLeft="true"
        android:layout_marginRight="10dp" />
    &lt;TextView android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/image"
        style="@style/NotificationTitle" />
    &lt;TextView android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/image"
        android:layout_below="@id/title"
        style="@style/NotificationText" />
&lt;/RelativeLayout>
</pre>

    <p>Notice that the two {@link android.widget.TextView} elements include the {@code style}
attribute. It's important that you use style resources for the text in your custom
notifications, because the background color of the notification can vary across different
devices and platform versions. Beginning with Android 2.3 (API level 9), the system defines a
style for the text it uses for the default notification layouts. Thus, you should apply
that style when running on Android 2.3 or higher to ensure that your text is visible against
the background.</p>

    <p>For example, to use the standard text colors on versions of Android lower than 2.3, you
should use the following styles for {@code res/values/styles.xml}:</p>
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;resources>
    &lt;style name="NotificationText">
      &lt;item name="android:textColor">?android:attr/textColorPrimary&lt;/item>
    &lt;/style>
    &lt;style name="NotificationTitle">
      &lt;item name="android:textColor">?android:attr/textColorPrimary&lt;/item>
      &lt;item name="android:textStyle">bold&lt;/item>
    &lt;/style>
    &lt;!-- If you want a slightly different color for some text,
         consider using ?android:attr/textColorSecondary -->
&lt;/resources>
</pre>
    <p>Then, to apply the system's default colors for notifications on Android
2.3 and higher, use the following styles for {@code res/values-v9/styles.xml}:</p>
<pre>
&lt;?xml version="1.0" encoding="utf-8"?>
&lt;resources>
    &lt;style name="NotificationText" parent="android:TextAppearance.StatusBar.EventContent" />
    &lt;style name="NotificationTitle" parent="android:TextAppearance.StatusBar.EventContent.Title" />
&lt;/resources>
</pre>
    <p>Now, when running on Android 2.3 (API level 9) or higher, the text in your custom view will
use the same colors that the system does for default notifications. This is important because later
versions of Android actually change the background color of the notifications to be dark. Inheriting
the system's styles ensures that your text will be light in such cases, but also if the background
is some other unexpected color, your text will also change as appropriate.</p>
  </li>

  <li>Now, in the application code, use the RemoveViews
    methods to define the image and text. Then pass the RemoteViews object to the <var>contentView</var>
    field of the Notification, as shown in this example:
<pre>
RemoteViews contentView = new RemoteViews(getPackageName(), R.layout.custom_notification_layout);
contentView.setImageViewResource(R.id.image, R.drawable.notification_image);
contentView.setTextViewText(R.id.title, "Custom notification");
contentView.setTextViewText(R.id.text, "This is a custom layout");
notification.contentView = contentView;
</pre>

    <p>As shown here, pass the application's package name and the layout
    resource ID to the RemoteViews constructor. Then, define the content for the ImageView and TextView,
    using the {@link android.widget.RemoteViews#setImageViewResource(int, int) setImageViewResource()}
    and {@link android.widget.RemoteViews#setTextViewText(int, CharSequence) setTextViewText()}.
    In each case, pass the reference ID of the appropriate View object that you want to set, along with
    the value for that View. Finally, the RemoteViews object is passed to the Notification in the
    <var>contentView</var> field.</p>
  </li>

  <li>Because you don't need the
    {@link android.app.Notification#setLatestEventInfo(Context,CharSequence,CharSequence,PendingIntent)
    setLatestEventInfo()} method when using a custom view, you must define the Intent for the Notification
    with the <var>contentIntent</var> field, as in this example:
<pre>
Intent notificationIntent = new Intent(this, MyClass.class);
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
notification.contentIntent = contentIntent;
</pre>
  </li>

  <li>The notification can now be sent as usual:
    <pre>mNotificationManager.notify(CUSTOM_VIEW_ID, notification);</pre>
  </li>
</ol>


<p>The {@link android.widget.RemoteViews} class also includes methods that you can use to easily add
a {@link android.widget.Chronometer} or {@link android.widget.ProgressBar}
in your notification's layout. For more information about creating custom layouts for your
notification, refer to the {@link android.widget.RemoteViews} class reference.</p>

<p class="caution"><strong>Caution:</strong>
When creating a custom notification layout, you must take special care to ensure that your
custom layout functions properly in different device orientations and resolutions. While this
advice applies to all View layouts created on Android, it is especially important in this case
because your layout real estate is very restricted. So don't make your custom layout too
complex and be sure to test it in various configurations.</p>