Ideal way to cancel an executing AsyncTask

Question

I am running remote audio-file-fetching and audio file playback operations in a background thread using AsyncTask. A Cancellable progress bar is shown for the time the fetch operation runs.

I want to cancel/abort the AsyncTask run when the user cancels (decides against) the operation. What is the ideal way to handle such a case?

Answer 1

Just discovered that AlertDialogs's boolean cancel(...); I've been using everywhere actually does nothing. Great.
So...

public class MyTask extends AsyncTask<Void, Void, Void> {      private volatile boolean running = true;     private final ProgressDialog progressDialog;      public MyTask(Context ctx) {         progressDialog = gimmeOne(ctx);          progressDialog.setCancelable(true);         progressDialog.setOnCancelListener(new OnCancelListener() {             @Override             public void onCancel(DialogInterface dialog) {                 // actually could set running = false; right here, but I'll                 // stick to contract.                 cancel(true);             }         });      }      @Override     protected void onPreExecute() {         progressDialog.show();     }      @Override     protected void onCancelled() {         running = false;     }      @Override     protected Void doInBackground(Void... params) {          while (running) {             // does the hard work         }         return null;     }      // ...  } 

Answer 2

If you're doing computations:

• You have to check isCancelled() periodically.

If you're doing a HTTP request:

• Save the instance of your HttpGet or HttpPost somewhere (eg. a public field).
• After calling cancel, call request.abort(). This will cause IOException be thrown inside your doInBackground.

In my case, I had a connector class which I used in various AsyncTasks. To keep it simple, I added a new abortAllRequests method to that class and called this method directly after calling cancel.