java.lang.Object | ||
↳ | android.content.BroadcastReceiver | |
↳ | android.support.v4.content.WakefulBroadcastReceiver |
Helper for the common pattern of implementing a BroadcastReceiver
that receives a device wakeup event and then passes the work off
to a Service
, while ensuring that the
device does not go back to sleep during the transition.
This class takes care of creating and managing a partial wake lock
for you; you must request the WAKE_LOCK
permission to use it.
A WakefulBroadcastReceiver
uses the method
startWakefulService()
to start the service that does the work. This method is comparable to
startService()
, except that
the WakefulBroadcastReceiver
is holding a wake lock when the service
starts. The intent that is passed with
startWakefulService()
holds an extra identifying the wake lock.
import android.content.Context; import android.content.Intent; import android.os.SystemClock; import android.support.v4.content.WakefulBroadcastReceiver; import android.util.Log; public class SimpleWakefulReceiver extends WakefulBroadcastReceiver { @Override public void onReceive(Context context, Intent intent) { // This is the Intent to deliver to our service. Intent service = new Intent(context, SimpleWakefulService.class); // Start the service, keeping the device awake while it is launching. Log.i("SimpleWakefulReceiver", "Starting service @ " + SystemClock.elapsedRealtime()); startWakefulService(context, service); } }
The service (in this example, an IntentService
) does
some work. When it is finished, it releases the wake lock by calling
completeWakefulIntent(intent)
. The intent it passes as a parameter
is the same intent that the WakefulBroadcastReceiver
originally
passed in.
import android.app.IntentService; import android.content.Intent; import android.os.SystemClock; import android.util.Log; public class SimpleWakefulService extends IntentService { public SimpleWakefulService() { super("SimpleWakefulService"); } @Override protected void onHandleIntent(Intent intent) { // At this point SimpleWakefulReceiver is still holding a wake lock // for us. We can do whatever we need to here and then tell it that // it can release the wakelock. This sample just does some slow work, // but more complicated implementations could take their own wake // lock here before releasing the receiver's. // // Note that when using this approach you should be aware that if your // service gets killed and restarted while in the middle of such work // (so the Intent gets re-delivered to perform the work again), it will // at that point no longer be holding a wake lock since we are depending // on SimpleWakefulReceiver to that for us. If this is a concern, you can // acquire a separate wake lock here. for (int i=0; i<5; i++) { Log.i("SimpleWakefulReceiver", "Running service " + (i+1) + "/5 @ " + SystemClock.elapsedRealtime()); try { Thread.sleep(5000); } catch (InterruptedException e) { } } Log.i("SimpleWakefulReceiver", "Completed service @ " + SystemClock.elapsedRealtime()); SimpleWakefulReceiver.completeWakefulIntent(intent); } }
Public Constructors | |||||||||||
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Public Methods | |||||||||||
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Finish the execution from a previous
startWakefulService(Context, Intent) .
| |||||||||||
Do a
Context.startService , but holding a wake lock while the service starts.
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Inherited Methods | |||||||||||
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From class
android.content.BroadcastReceiver
| |||||||||||
From class
java.lang.Object
|
Finish the execution from a previous startWakefulService(Context, Intent)
. Any wake lock
that was being held will now be released.
intent | The Intent as originally generated by startWakefulService(Context, Intent) . |
---|
Do a Context.startService
, but holding a wake lock while the service starts.
This will modify the Intent to hold an extra identifying the wake lock;
when the service receives it in Service.onStartCommand
, it should pass back the Intent it receives there to
completeWakefulIntent(android.content.Intent)
in order to release
the wake lock.
context | The Context in which it operate. |
---|---|
intent | The Intent with which to start the service, as per
Context.startService .
|