Android AsyncTask - why is doInBackground() not executed?

Question

I have a nested fragment containing the following method:

public void onSave() {
    if (getActivity() == null || view == null) return;
    if (file != null && file.exists()) {
        new AsyncTask<Void, Void, Void>() {
            @Override
            protected void onPreExecute() {
                Log.d("log", "onPreExecute of save ex");
            }

            @Override
            protected Void doInBackground(Void... params) {

                Log.d("log", "doInBackground of save ex");
                //DO SOMETHING
                return null;
            }

            protected void onPostExecute(Void result) {
                BaseFragment fragment = new LocalListFragment();
                ((LocalLauncherFragment)(LocalEditFragment.this.getParentFragment())).setFragment(fragment);
                Log.d("log", "end of save ex");
            };
        }.execute();
    } else {
        showAlert();
    }
}

My problem is that if I call this method for the first time, it executes until onPostExecute(). However if I go to other fragment and opens this fragment newly(by creating a new fragment object and replacing to it) then only onPreExecute() is executed. Why doesn't this asyncTask object get executed well for the second time?

Intestingly if I use executeOnExecutor() then it works fine for the second time. But why doesn't execute() work? Is AsyncTask's life tied to fragment or something?

Thanks in advance!

Answer 1

It sounds to me like something is hanging in the AsyncTask. In modern versions of Android AsyncTasks run on a single thread unless you specify an Executor that's multi-threaded. onPreExecute() still runs successfully because that runs on the main thread. You never see doInBackground the second time though because the single background thread is still hung from the first call. You'll need to examine the contents of LocalKeekLauncherFragment.setFragment(fragment) to see what's causing the hang.