应用关闭后后台进程（AsyncTask）仍在运行

Question

My app has 3 or 4 async tasks, two of which get data from an sqlite database and create intents to send it to a receiver in the main activity. It all works fine - until I close the app and then restart it. The data is then not received correctly. After a lot of experimentation I discovered that if, after closing the app normally, I 'force stop' it, it works fine again - until the next time I run the task and again close the app. This behaviour doesn't show itself normally when running on the debugger. However, if I start the app on the device (rather than via Android Studio) and then attach the debugger, I can see quite clearly that the receiver is receiving two copies of the broadcast each time, instead of only one. One copy is correct, the other contains rubbish data. I have addded extra lines which show that the task ID is the same in each case.

The sending intent looks like this

private void sendRoads(ArrayList<RedRoad> roadsChunk)
{
    ArrayList<RedRoad> theseRoads = new ArrayList<>(roadsChunk);
    Intent mapIntent = new Intent("newRoads");
    mapIntent.putParcelableArrayListExtra("newRoads", theseRoads);
    mapIntent.putExtra("chunkIndex",cIndex++);

    int threadID = android.os.Process.getThreadPriority(android.os.Process.myTid());
    mapIntent.putExtra("threadID",threadID);

    LocalBroadcastManager.getInstance(ctx).sendBroadcast(mapIntent);
    // get ready for next group while we show these
    roadsChunk.clear();
}

In order to try to solve this I have added extra lines to onDestroy:

    @Override
public void onDestroy() {
    super.onDestroy();
    if (roadCreation!=null)
        roadCreation.cancel(true);
    if (parseKmlFile != null)
        parseKmlFile.cancel(true);
    Intent serviceIntent = new Intent(getApplicationContext(), LocationService.class);
    stopService(serviceIntent);
}

but that appears to have made no difference (the two classes named are the two which use the method above. As you can see, there is also a service involved but I can tell by other means that it is stopping correctly).

I have tried to catch the erroneous broadcasts and ignore any action on them, but they still mess up the correct data.

I have two test devices; one sdk 26 (Oreo) and one 29 (Q); the latter is showing this problem evry time, the former only occasionally.

Answer 1

Thanks to this answer I have solved this at last. My onDestroy() now look like this:

public void onDestroy() {
    super.onDestroy();
    Intent serviceIntent = new Intent(getApplicationContext(), LocationService.class);
    stopService(serviceIntent);
    // ensure all background tasks stop correctly
    int id= android.os.Process.myPid();
    android.os.Process.killProcess(id);
}