Cannot cancel running AsyncTask in AsyncTaskLoader

Question

I want to cancel running AsyncTask (in AsyncTaskLoader) when the user clicks the home button. Here is what I created so far:

package cz.davidliska.android.lo         


        

Answer 1

If you mean "Is there any chance to cancel running AsyncTask in android.content.AsyncTaskLoader?" the answer is yes: you just need to add some "cancel points" in your loadInBackground method and check whether a cancellation request has been issued (isLoadInBackgroundCanceled() == true), then either return or throw an OperationCanceledException).

The support library version of AsyncTaskLoader you are using though doesn't seem to fully implement cancellation at this time (not in mid-flight at least, and a cursory comparison of the framework and of the support version of Loader seems to suggest that cancellation might not be supported at all...).

http://developer.android.com/reference/android/content/Loader.html http://developer.android.com/reference/android/support/v4/content/Loader.html

Two ways to alleviate the problem come to my mind:

• create two implementations of your Loader (one using the framework for API level 11 and above, and one without the cancel feature for older devices)
• create an android.support.v4.content.Loader subclass and handle each AsyncTask and cancellation request yourself

Answer 2

public boolean cancelLoad() {
    ...
    boolean cancelled = mTask.cancel(false);
}



        @Override
        public Date loadInBackground() { // AsyncTaskLoader only
            Log.d(TAG, "Loader.loadInBackground()");

            try {
                // there will be some HttpClient.execute()
                while(true) {
                    Thread.sleep(100);
                    Log.d(TAG, "Loader.loadInBackground() still running");

                   if(cancelled)                 <---------
                      return new Date();         <----------
                }

            } catch (InterruptedException e) {
                Log.d(TAG, "Loader.loadInBackground() interupted");
            }
            Log.d(TAG, "Loader.loadInBackground() finished");
            return new Date();
        }