android: how to receive broadcast from service when the app is inactive

Question

When my service is running and I can see my app on the screen, everything works fine. My service sends broadcast messages and I can see them in my "MainActivity". But as soon as I push the home button and my app is no longer in the foreground, it stops. The service is still running but the broadcasts don't arrive at my "dead" or "pausing" app. This is my code:

Main Activity:

onCreate:

    Intent intent = new Intent(getApplicationContext(), MainGate_Service.class);
    startService(intent);

@Override
protected void onStart() {
    super.onStart();

    LocalBroadcastManager.getInstance(this).registerReceiver(ServiceReceiver, new IntentFilter("MainGate_ring"));
}

@Override
protected void onStop() {
    super.onStop();

    LocalBroadcastManager.getInstance(this).unregisterReceiver(ServiceReceiver);
}


private BroadcastReceiver ServiceReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context context, Intent intent) {

        String message = intent.getStringExtra("ServiceMessage");

        if(message != null) {
            if(alarmActive && message.equals("ring"))
                new soundPlayer().execute();
        }

        setNoti(message);

    }
}

Service:

@Override
protected void onHandleIntent(Intent intent) {

    ring = rcv_ring();

    Intent ServiceIntent = new Intent("MainGate_ring");
    ServiceIntent.putExtra("ServiceMessage", ring);
    LocalBroadcastManager.getInstance(this).sendBroadcast(ServiceIntent);


}

I think your logic has some issues. Whatever it is you need to do why don't you do it inside the service? — Naveen Dissanayake, Nov 04 '16 at 06:21
just register your receiver in manifest not inside activity. — Radhey, Nov 04 '16 at 07:04

score 1 · Answer 1 · answered Nov 04 '16 at 07:55

whenever you press home button onStop gets call and there you are unregister receiver so there is not broadcast receiver who can receive broadcast.

LocalBroadcastManager.getInstance(this).unregisterReceiver(ServiceReceiver);

Remove above line from onStop() or unregister it whenever your service stop.

score 0 · Answer 2 · answered Nov 04 '16 at 06:24

0

onStop#LocalBroadcastManager.getInstance(this).unregisterReceiver(ServiceReceiver);

literally unregister receiver. So there is no receiver to receive broadcasted message from service.

answered Nov 04 '16 at 06:24

Sung Min Lee

154
7

score 0 · Answer 3 · answered Nov 04 '16 at 06:29

The problem is here

@Override
protected void onStop() {
    super.onStop();

    LocalBroadcastManager.getInstance(this).unregisterReceiver(ServiceReceiver);
}

Activity.onStart() :

Called after onCreate(Bundle) — or after onRestart() when the activity had been stopped, but is now again being displayed to the user. It will be followed by onResume().

Activity.onStop()

Called when you are no longer visible to the user. You will next receive either onRestart(), onDestroy(), or nothing, depending on later user activity.

So as soon as you leave your activity onStop() is called and you unregister your receiver.

Don't put your unregister code in onDestroy() either, because it may or may not be called and the Activity might be killed without calling it.

As suggested by @Naveen Dissanayake you might want to reconsider your logic.

score 0 · Answer 4 · answered Nov 04 '16 at 06:42

You register your BroadcastReceiver inside activity, so, it will depend on Activity's lifecycle. When you press back button, activity goes into 'stopped' state - methods onPause and onStop is called. Android can also destroy this activity in it is low on resources. Service, on the other hand, i smeant to be running inndefinetely, even when ui is not ready. If you wanat to receive notifications from Activity, there is two possible solutions: - Create, store and manage BroadcastReceiver in Application instance - Application class is still running until your app is destroyed. It seems like you want to play sound when service notify you about some action. Register BroadcastReceiver in onCreate and unregister in onDestroy in notifications. - Another solution - use another Service if you want to trigger some action or IntentService, reacting to that broadcast. I woud consider solution - create some ResponseService, start it along with your MainGate_Service (from Application) and stop it from application too. In that Service register BroadcastReceiver or, add IntentFilter into manifest if you want it to start even when app is not running. In your Activity, bind to that service. Serive will know if some UI is attached (if Activity is bound), and, if it is, will notify activity. If it don't - will do some other things (perhaps, show notification)

score 0 · Answer 5 · answered Apr 18 '19 at 06:29

If you want to receive Broadcast even if your Activity is in Background then,

Register in onCreate(...)

@Override
protected void onCreate(Bundle sis) {
    super.onCreate(sis);
    setContentView(...);
    LocalBroadcastManager.getInstance(this).registerReceiver(ServiceReceiver, new IntentFilter("MainGate_ring"));
}

Unregister in onDestroy()

@Override
protected void onDestroy() {
    super.onDestroy();
    LocalBroadcastManager.getInstance(this).registerReceiver(ServiceReceiver, new IntentFilter("MainGate_ring"));
}

android: how to receive broadcast from service when the app is inactive

5 Answers5

Register in onCreate(...)

Unregister in onDestroy()