Android：停止前台服务导致应用程序崩溃

Question

Prerequisites: As a part of the requirement for my application, I need to make sure that the application won't be closed (killed) by the Android system while in background. For this purpose I implemented Foreground service, even though I don't do any actual process in background, just maintaining the state of the application. Everything works just fine, except one thing which is not fully clear to me how to fix.

The issue: Sometimes (only once, for now), I receive this exception:

android.app.RemoteServiceException: Context.startForegroundService() did not then call Service.startForeground(): 

This exception is thrown when I'm trying to stop the foreground service while it wasn't actually started.

So, my question is - is there is a way to stop foreground service properly, making sure that it is not running before actually stopping it? What I found at the moment is that I can have static instance for my service and compare to null before stopping service, or get the list of all services currently running. But all these look like some "hack" workarounds.

Here some code: MyForegroundService:

public class ForegroundService extends Service {

public static final int NOTIFICATION_ID = 1;
public static final String CHANNEL_ID = "SessionForegroundServiceChannel";
public static final String ACTION_FOREGROUND_START = "ACTION_FOREGROUND_START";
public static final String ACTION_FOREGROUND_STOP = "ACTION_FOREGROUND_STOP";

public static void startForegroundService(Context context) {
    Intent intent = new Intent(context, ForegroundService.class);
    intent.setAction(ForegroundService.ACTION_FOREGROUND_START);
    ContextCompat.startForegroundService(context, intent);
}

public static void stopForegroundService(Context context) {
    Intent intent = new Intent(context, ForegroundService.class);
    intent.setAction(ForegroundService.ACTION_FOREGROUND_STOP);
    ContextCompat.startForegroundService(context, intent);
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    if (ACTION_FOREGROUND_START.equals(intent.getAction())) {
        createNotificationChannel();
        Intent stopForegroundIntent = new Intent(this, ForegroundServiceBroadcastReceiver.class);
        PendingIntent pendingLogoutIntent = PendingIntent.getBroadcast(this,
                0, stopForegroundIntent, PendingIntent.FLAG_UPDATE_CURRENT);

        Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
                .setContentTitle(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O
                        ? null
                        : getString(R.string.app_short_name))
                .setContentText(getString(R.string.foreground_description))
                .setColor(getResources().getColor(R.color.color))
                .setSmallIcon(R.drawable.ic_notification)
                .addAction(R.drawable.ic_logout, getString(R.string.logout), pendingLogoutIntent)
                .build();
        startForeground(NOTIFICATION_ID, notification);
    } else if (ACTION_FOREGROUND_STOP.equals(intent.getAction())) {
        stopForeground(true);
        stopSelf();
    }
    return START_STICKY;
}

private void createNotificationChannel() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        NotificationChannel serviceChannel = new NotificationChannel(
                CHANNEL_ID,
                getString(R.string.app_name),
                NotificationManager.IMPORTANCE_LOW
        );
        NotificationManager manager = getSystemService(NotificationManager.class);
        manager.createNotificationChannel(serviceChannel);
    }
}


@Nullable
@Override
public IBinder onBind(Intent intent) {
    return null;
}

}

<service
        android:name=".ui.ForegroundService"
        android:exported="false"
        android:stopWithTask="true"/>

I also have BroadcastReceiver and EventBus to listen to some events and stop foreground depending on those events.

Can you please help me, guys?

Answer 1

Let me add more details to what @Pawel commented:

You get this exception if you don't call Service.startForeground within 3 seconds of calling Context.startForegroundService that's all there's to it.

Here is how the complete solution will look like:

When it comes to the case when you need to stop a foreground service you need to do the following (pseudo code):

if (action == START_FOREGROUND) {
    ...
    startForeground(NOTIFICATION_ID, notification);
} else if (action == STOP_FOREGROUND) {
    startForeground(NOTIFICATION_ID, closeNotification); //in case it wasn't started before
    stopForeground(true);
    stopSelf();
}

Even though it is not obvious, and any documentation don't directly say that when you need to stop foreground you need to start foreground before stopping it (if it wasn't started).

Thanks @Pawel for the hint.