Android: got CalledFromWrongThreadException in onPostExecute() - How could it be?

Question

I have an app in production for a few weeks, using ACRA, and I had zero errors until one strange error reported today.

I\'ve got:

    android.view.Vi         


        

Answer 1

Placing the following line of code in the Application onCreate should solve the problem:

     /**
     * Fixing AsyncTask Issue not called on main thread
     */
    try {
        Class.forName("android.os.AsyncTask");
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }

It seems the issue is created when the AsyncTask class is first initiated on a different main Thread which is not our main Thread, I checked it by adding the code in the bottom, to my Application onCreate

    new Thread(new Runnable() {


        @Override
        public void run() {

            Log.i("tag","1.3onPostExecute ran ON: " + Thread.currentThread().getId());
            Looper.prepare();
            new AsyncTask(){
                @Override
                protected Void doInBackground(Void... params) {
                    Log.i("tag","2onPostExecute ran ON: " + Thread.currentThread().getId());
                    return null;
                }

                @Override
                protected void onPostExecute(Void aVoid) {
                    Log.i("tag","1.2onPostExecute ran ON: " + Thread.currentThread().getId());
                    super.onPostExecute(aVoid);
                }
            }.execute();
            Looper.loop();
            Looper.myLooper().quit();
        }
    }).start();

This code will init the AsynTask in a main Thread which is not the application main, and will cause the application to crash in any other AsyncTask which will do any UI on the post-execute. crashing with the CalledFromWrongThreadException

Hope it cleared things a little bit more.

Thanks all for the great help on this.