Service not starting on Oreo in app widget using P

问题:

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 (no longer active).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.

回答1:

As you note, an app widget does not count for the PendingIntent background whitelist. I do not know why — it would seem to be about on par with a PendingIntent started by a Notification. Perhaps it's an issue that the Notification is a system thing, whereas the app widget is a home screen thing. Regardless, you could:

• Use getForegroundService(), as you have, or

• Try getBroadcast() with an explicit Intent, and with the BroadcastReceiver starting a JobIntentService, if you do not want to raise a Notification (as a foreground service requires)

Based on your symptoms, you appear to have tripped over what I would consider to be a bug: there should be a way to switch from getService() to getForegroundService() without having to reboot. :-) I'll try to run some experiments and will file an issue if I can reproduce the problem.

回答2:

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 pending intent pointing to a service, but you can use one pointing to an activity or broadcast receiver.

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:
   enqueueWork(context, MyWidgetService.class, JOB_ID, intent);
   , where JOB_ID is just an unique integer constant, must be the same value for all work enqueued for the same class.
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);
   , and then in onReceive start the service using enqueueWork:
   @Override public void onReceive(Context context, Intent intent) { super.onReceive(context, intent); if (intent.getAction().equals("SOME_UNIQUE_ACTION")) { MyWidgetService.enqueueWork(.....); } }
   If your PendingIntent was starting the activity, just leave it be - it'll work just fine on android 8.0+.
6. 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.

回答3:

Could goasyc be an option? You could change your PendingIntent to fire a BroadcastReceiver, then in the OnRecieve method, you can call goasync() Then you should be able to use the PendingResult it generates to create an async call. Still don't think you can start a service.

How to use "goAsync" for broadcastReceiver?