How to display push notifcation from background service in Android O // how to use startForeground() correctly

Question

I'm trying to show a push notification triggered by a GCM-Message. The GCM message is received by the broadcast receiver in the background, yet the Push Notification is not shown.

I minified my code for demonstration purposes:

The BroadcastReceiver (Logging tells me that onReceive() is called)

public class GcmBroadcastReceiver extends BroadcastReceiver {
    private static final String TAG = GcmBroadcastReceiver.class.getName();

    @RequiresApi(api = Build.VERSION_CODES.O)
    @Override
    public void onReceive(Context context, Intent intent) {
        Log.d(TAG, "received GCM intent: "+intent.toString());
        ComponentName comp = new ComponentName(context.getPackageName(), GcmIntentService.class.getName());
        context.startForegroundService(intent.setComponent(comp));
    }
}

The Intent that should should fire the notification. Logging says that onHandleIntent() is called.

@RequiresApi(api = Build.VERSION_CODES.O)
public class GcmIntentService extends IntentService {
    private static final String TAG = GcmIntentService.class.getName();

    public GcmIntentService() { super("GcmIntentService"); }

    @Override
    protected void onHandleIntent(Intent intent) {
        Log.d(TAG,"received intent");
        String channelId = "MyChannelId";
        Notification notification = new NotificationCompat.Builder(getApplication(), channelId)
                .setSmallIcon(R.drawable.ic_launcher)
                .setContentTitle("MyTitle")
                .setContentText("MyText")
                .build();

        NotificationChannel channel = new NotificationChannel(channelId, "foo", NotificationManager.IMPORTANCE_HIGH);
        NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        manager.createNotificationChannel(channel);

        startForeground(1, notification);
        manager.notify(1, notification);
    }
}

My AndroidManifest.xml:

    <receiver
        android:name=".cdmclient.GcmBroadcastReceiver"
        android:permission="com.google.android.c2dm.permission.SEND" >
        <intent-filter>
            <action android:name="com.google.android.c2dm.intent.RECEIVE" />
            <action android:name="com.google.android.c2dm.intent.REGISTRATION" />
            <category android:name="${applicationId}.cdmclient" />
        </intent-filter>
    </receiver>

    <service android:name=".cdmclient.GcmIntentService" android:exported="false"/>

When the app is in the foreground when a GCM event is received, the log shows:

D/de.locked.bob.cdmclient.GcmBroadcastReceiver: received GCM intent: Intent { act=com.google.android.c2dm.intent.RECEIVE flg=0x1000010 pkg=de.locked.bob.debug cmp=de.locked.bob.debug/de.locked.bob.cdmclient.GcmBroadcastReceiver (has extras) }
D/de.locked.bob.cdmclient.GcmIntentService: received intent
E/EnhancedIntentService: binding to the service failed

When the app is in the background when a GCM event is received, the log shows:

D/de.locked.bob.cdmclient.GcmBroadcastReceiver: received GCM intent: Intent { act=com.google.android.c2dm.intent.RECEIVE flg=0x1000010 pkg=de.locked.bob.debug cmp=de.locked.bob.debug/de.locked.bob.cdmclient.GcmBroadcastReceiver (has extras) }
D/de.locked.bob.cdmclient.GcmIntentService: received intent
W/EnhancedIntentService: Service took too long to process intent: com.google.android.c2dm.intent.RECEIVE App may get closed.

And of course, no notification shows up. I guess I'm using startForeground(..) and startForegroundService(...) in a wrong way but I'm out of ideas currently.

Answer 1

IntentServices are not meant to be started as Foreground Services (refer: Using startForeground() with an Intent Service)

Is it your intention to start a Service when the push notification arrives from GCM? You do not need the service to show the notification; you could do that from your BroadcastReceiver just like you did in the Service.