training/run-background-service/report-status.jd

page.title=Reporting Work Status
trainingnavtop=true
@jd:body
<div id="tb-wrapper">
<div id="tb">
<h2>This lesson teaches you to</h2>
<ol>
    <li>
        <a href="#ReportStatus">Report Status From an IntentService</a>
    </li>
    <li>
        <a href="#ReceiveStatus">Receive Status Broadcasts from an IntentService</a>
    </li>
</ol>
<h2>You should also read</h2>
<ul>
    <li>
        <a href="{@docRoot}guide/components/intents-filters.html">Intents and Intent Filters</a>
    </li>
    <li>
        The section <b>Broadcast receivers</b> in the
    <a href="{@docRoot}guide/components/fundamentals.html#Components">Application Components</a>
        API guide.
    </li>
</ul>
<h2>Try it out</h2>

<div class="download-box">
    <a href="{@docRoot}shareables/training/ThreadSample.zip" class="button">Download the sample</a>
    <p class="filename">ThreadSample.zip</p>
</div>

</div>
</div>
<p>
    This lesson shows you how to report the status of a work request run in a background service
    to the component that sent the request. This allows you, for example, to report the status of
    the request in an {@link android.app.Activity} object's UI. The recommended way to send and
    receive status is to use a {@link android.support.v4.content.LocalBroadcastManager}, which
    limits broadcast {@link android.content.Intent} objects to components in your own app.
</p>
<h2 id="ReportStatus">Report Status From an IntentService</h2>

<p>
    To send the status of a work request in an {@link android.app.IntentService} to other
    components, first create an {@link android.content.Intent} that contains the status in its
    extended data. As an option, you can add an action and data URI to this
    {@link android.content.Intent}.
</p>
<p>
    Next, send the {@link android.content.Intent} by calling
    {@link android.support.v4.content.LocalBroadcastManager#sendBroadcast
    LocalBroadcastManager.sendBroadcast()}. This sends the {@link android.content.Intent} to any
    component in your application that has registered to receive it.
    To get an instance of {@link android.support.v4.content.LocalBroadcastManager}, call
    {@link android.support.v4.content.LocalBroadcastManager#getInstance getInstance()}.
</p>
<p>
    For example:
</p>
<pre>
public final class Constants {
    ...
    // Defines a custom Intent action
    public static final String BROADCAST_ACTION =
        "com.example.android.threadsample.BROADCAST";
    ...
    // Defines the key for the status "extra" in an Intent
    public static final String EXTENDED_DATA_STATUS =
        "com.example.android.threadsample.STATUS";
    ...
}
public class RSSPullService extends IntentService {
...
    /*
     * Creates a new Intent containing a Uri object
     * BROADCAST_ACTION is a custom Intent action
     */
    Intent localIntent =
            new Intent(Constants.BROADCAST_ACTION)
            // Puts the status into the Intent
            .putExtra(Constants.EXTENDED_DATA_STATUS, status);
    // Broadcasts the Intent to receivers in this app.
    LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);
...
}
</pre>
<p>
    The next step is to handle the incoming broadcast {@link android.content.Intent} objects in
    the component that sent the original work request.
</p>
<h2 id="ReceiveStatus">Receive Status Broadcasts from an IntentService</h2>
<p>

    To receive broadcast {@link android.content.Intent} objects, use a subclass of
    {@link android.content.BroadcastReceiver}. In the subclass, implement the
    {@link android.content.BroadcastReceiver#onReceive BroadcastReceiver.onReceive()} callback
    method, which {@link android.support.v4.content.LocalBroadcastManager} invokes when it receives
    an {@link android.content.Intent}. {@link android.support.v4.content.LocalBroadcastManager}
    passes the incoming {@link android.content.Intent} to
    {@link android.content.BroadcastReceiver#onReceive BroadcastReceiver.onReceive()}.
</p>
<p>
    For example:
</p>
<pre>
// Broadcast receiver for receiving status updates from the IntentService
private class ResponseReceiver extends BroadcastReceiver
{
    // Prevents instantiation
    private DownloadStateReceiver() {
    }
    // Called when the BroadcastReceiver gets an Intent it's registered to receive
    &#64;
    public void onReceive(Context context, Intent intent) {
...
        /*
         * Handle Intents here.
         */
...
    }
}
</pre>
<p>
    Once you've defined the {@link android.content.BroadcastReceiver}, you can define filters
    for it that match specific actions, categories, and data. To do this, create
    an {@link android.content.IntentFilter}. This first snippet shows how to define the filter:
</p>
<pre>
// Class that displays photos
public class DisplayActivity extends FragmentActivity {
    ...
    public void onCreate(Bundle stateBundle) {
        ...
        super.onCreate(stateBundle);
        ...
        // The filter's action is BROADCAST_ACTION
        IntentFilter mStatusIntentFilter = new IntentFilter(
                Constants.BROADCAST_ACTION);

        // Adds a data filter for the HTTP scheme
        mStatusIntentFilter.addDataScheme("http");
        ...
</pre>
<p>
    To register the {@link android.content.BroadcastReceiver} and the
    {@link android.content.IntentFilter} with the system, get an instance of
    {@link android.support.v4.content.LocalBroadcastManager} and call its
    {@link android.support.v4.content.LocalBroadcastManager#registerReceiver registerReceiver()}
    method. This next snippet shows how to register the {@link android.content.BroadcastReceiver}
    and its {@link android.content.IntentFilter}:
</p>
<pre>
        // Instantiates a new DownloadStateReceiver
        DownloadStateReceiver mDownloadStateReceiver =
                new DownloadStateReceiver();
        // Registers the DownloadStateReceiver and its intent filters
        LocalBroadcastManager.getInstance(this).registerReceiver(
                mDownloadStateReceiver,
                mStatusIntentFilter);
        ...
</pre>
<p>
    A single {@link android.content.BroadcastReceiver} can handle more than one type of broadcast
    {@link android.content.Intent} object, each with its own action. This feature allows you to
    run different code for each action, without having to define a separate
    {@link android.content.BroadcastReceiver} for each action. To define another
    {@link android.content.IntentFilter} for the same
    {@link android.content.BroadcastReceiver}, create the {@link android.content.IntentFilter} and
    repeat the call to
    {@link android.support.v4.content.LocalBroadcastManager#registerReceiver registerReceiver()}.
    For example:
</p>
<pre>
        /*
         * Instantiates a new action filter.
         * No data filter is needed.
         */
        statusIntentFilter = new IntentFilter(Constants.ACTION_ZOOM_IMAGE);
        ...
        // Registers the receiver with the new filter
        LocalBroadcastManager.getInstance(getActivity()).registerReceiver(
                mDownloadStateReceiver,
                mIntentFilter);
</pre>
<p>
    Sending an broadcast {@link android.content.Intent} doesn't start or resume an
    {@link android.app.Activity}. The {@link android.content.BroadcastReceiver} for an
    {@link android.app.Activity} receives and processes {@link android.content.Intent} objects even
    when your app is in the background, but doesn't force your app to the foreground. If you
    want to notify the user about an event that happened in the background while your app was not
    visible, use a {@link android.app.Notification}. <i>Never</i> start an
    {@link android.app.Activity} in response to an incoming broadcast
    {@link android.content.Intent}.
</p>
<p>

</p>