Android using a Wake Lock with Foreground service?

Question

I'm working on an audio app utilizing exoplayer in a foreground service to allow the audio to play with the screen off. This appears to work as intended, but somewhere I read something about adding Wake Locks.

Is that something that would be necessary with a foreground service? The Wake Lock is used to keep the CPU awake, but the foreground service seems to do that while the service is playing.

I decided to test it on the way to work and it played audio with the screen off for +20 minutes without problems. I assume ~20 mins would be long enough for the OS to shut something down without a wake lock.

user_10357086 · Answer

Yes, Wake lock is used when you start the service again after the device has been rebooted or when the service is killed.

Use it like this:

Create BroadcastReceiver for receiving the broadcast to start a service.

public class AutoStart extends BroadcastReceiver {
  LocalReceiver localReceiver = new LocalReceiver();
     public void onReceive(Context context, Intent intent) {
         if (intent.getAction().equals(Intent.ACTION_BOOT_COMPLETED)) {
         Intent intent2 = new Intent(context, YourService.class);
         if (Build.VERSION.SDK_INT >= 26)
             context.startForegroundService(intent2);
         else
             context.startService(intent2);
        localReceiver.startMainService(context); //It will create a receiver to receive the broadcast & start your service in it's `onReceive()`.
      }
   }
}

Register that receiver in the Manifest with ACTION_BOOT_COMPLETED intent-filter.
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Now we have created the receiver which will receive a broadcast only one time when the device is rebooted. So we have to use wakelock manager to keep the register our service within a limited time.

Now, create the broadcast receiver which will be used to receive the broadcast to start the service.

public class LocalReceiver extends BroadcastReceiver {
    PowerManager.WakeLock wakeLock = ((PowerManager) context.getSystemService(Context.POWER_SERVICE)).wakeLock(PowerManager.PARTIAL_WAKE_LOCK, ":YourService");
    wakeLock.acquire(60 * 1L); //It will keep the device awake & register the service within 1 minute time duration.
    context.getPackageManager().setComponentEnabledSetting(new ComponentName(context, YourService.class), 1, 1);

    playMusic(); //Play your audio here.

    wakeLock.release(); //Don't forget to add this line when using the wakelock
}

Now create a method in LocalReceiver to send the broadcast to start the service.

public void startMainService(Context context) {
    PendingIntent broadcast = PendingIntent.getBroadcast(context, REQUEST_CODE, new Intent(context, LocalReceiver.class), 0);
}

That's it! We've successfully implemented the wake lock. Now, whenever you want to play a sound. Just send the broadcast to the LocalReceiver & it will get your job done.

Also, don't forget to register this receiver in the Manifest as well as add android:enabled="true" and android:exported="true" where you register your service in Manifest.

NOTE : We have used playMusic() inside the onReceive(). So it will also play the audio when the device is rebooted & the service will be registered. If you just want to bind the service on reboot, then you can simply add startService() method inside the onReceive() instead of the playMusic().

Android using a Wake Lock with Foreground service?

1 Answers