How to remove all notifications when an android app (activity or service) is killed?

@See public void onTaskRemoved(Intent rootIntent). This is called if the service is currently running and the user has removed a task that comes from the service's application. If you have set ServiceInfo.FLAG_STOP_WITH_TASK flag then you will not receive this callback; instead, the service will simply be stopped.

You can remove all notifications that your app has created with cancelAll():

NotificationManager nManager = ((NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE));
nManager.cancelAll();

According to the API docs, this will

Cancel all previously shown notifications.

in the same way that cancel(int id) does:

Cancel a previously shown notification. If it's transient, the view will be hidden. If it's persistent, it will be removed from the status bar.

It seems that

onTaskRemoved

of the Service DOES get called when the user kills the application task (by swiping out the app in the "task manager". I am able to remove the Notification from here.