Service not starting on Oreo in app widget using PendingIntent

Question

I'm using Android app widgets. I'm creating a PendingIntent object and use it in the method RemoteViews#setOnClickPendingIntent(). This is the pending intent:

// The below code is called in the onUpdate(Context, AppWidgetManager, int[]) method of the AppWidgetProvider class.

// Explicit intent
Intent intent = new Intent(context, MyService.class);
intent.setAction(MY_ACTION);
intent.putExtra(EXTRA_KEY, VALUE);

// Create the pending intent
PendingIntent pendingIntent = PendingIntent.getService(context, appWidgetId, intent, 0);

// 'views' is a RemoteViews object provided by onUpdate in the AppWidgetProvider class.
views.setOnClickPendingIntent(R.id.root_layout, pendingIntent);

The above code works as expected before Android Oreo. However, in Android Oreo it no longer starts the service if the app is swiped away from recents. (no longer active). Aren't PendingIntents excluded in Oreo's background execution limits?

For testing purposes I replaced getService with getForegroundService but the Service is still not started. Both methods show the below message in the log:

W/ActivityManager: Background start not allowed: service Intent { act=com.example.myapp.MY_ACTION flg=0x10000000 cmp=com.example.myapp/com.example.myapp.MyService bnds=[607,716][833,942] (has extras) } to com.example.myapp/com.example.myapp.MyService from pid=-1 uid=10105 pkg=com.example.myapp

Why is the Service not started, even when using getForegroundService? I tested this on a Nexus 6P running Android 8.1.0.

Answer 1

You can no longer start a service in background in 8.0, but you can use JobScheduler to achieve similar results. There is also a JobIntentService helper class that allows you to switch to JobScheduler from service without much refatoring. And you cannot use PendingIntent pointing to a service, but you can use one pointing to an Activity or BroadcastReceiver.

If you had a working widget pre 8.0, and now you need to make it work on android 8.0, just perform this simple steps:

1. Change your IntentService class to JobIntentService
2. Rename service onHandleIntent method to onHandleWork (same parameters)
3. Add BIND_JOB_SERVICE permission to your service in the manifest:

    <service android:name=".widget.MyWidgetService"
           android:permission="android.permission.BIND_JOB_SERVICE">
    </service>

4. To start this service, you must no longer use context.startService. Instead use enqueueWork static method (where JOB_ID is just an unique integer constant, must be the same value for all work enqueued for the same class):

    enqueueWork(context, MyWidgetService.class, JOB_ID, intent);

5. For clicks, replace your pendingIntent that was pointing to service with a pendingIntent that points to a BroadcastReceiver. Since your subclass of AppWidgetProvider is a BroadcastReceiver itself, you might as well use it:

    Intent myIntent = new Intent(context, MyAppWidgetProvider.class);
    myIntent .setAction("SOME_UNIQUE_ACTION");
    pendingIntent = PendingIntent.getBroadcast(context, 0, myIntent, PendingIntent.FLAG_UPDATE_CURRENT);

6. In onReceive start the service using enqueueWork (If your PendingIntent was starting the activity, just leave it be - it'll work just fine on android 8.0+):

    @Override
    public void onReceive(Context context, Intent intent) {
        super.onReceive(context, intent);
        if (intent.getAction().equals("SOME_UNIQUE_ACTION")) {
            MyWidgetService.enqueueWork(.....);
        }
    }

7. To ensure that the widget will work on old devices, make sure you have WAKE_LOCK permission in your manifest (used by JobIntentService on old devices).

That's it. This widget will now work properly on both new and old devices. The only real difference will be that if your 8.0 device is in doze mode it may not update widget all that often, but that shouldn't be a problem because if it is dozing, that means that user can't see your widget right now anyways.