Stop AsyncTask in Fragments when Back Button is pressed

Question

i have an activities that host fragments. pressing a button goes from fragment A to fragment B through a FragmentTransaction and the added to the back stack. Now fragment B

Answer 1

Just call this code in the onBackPressed()-method of your hosting Activity - same applies to a Fragment via onDestroy():

if(myFancyAsyncTask != null && myFancyAsyncTask.getStatus() == Status.RUNNING) {
  myFancyAsyncTask.cancel(true);
}

This will cancel a running AsyncTask for you. Be sure to check back in the AsyncTask if it was not cancelled by using the lifecycle-methods:

protected void onPostExecute(Long result) {
     if(!isCancelled()) {
       // do your work
     }
 }