Attempts to cancel execution of this task. This attempt will fail if the task has already completed, already been cancelled, or could not be cancelled for some other reason. If successful, and this task has not started when cancel is called, this task should never run. If the task has already started, then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted in an attempt to stop the task.

Calling this method will result in AsyncTask`3.onCancelled(Result) being invoked on the UI thread after AsyncTask`3.doInBackground(Params...) returns. Calling this method guarantees that AsyncTask`3.onPostExecute(Result) is never invoked. After invoking this method, you should check the value returned by AsyncTask`3.isCancelled() periodically from AsyncTask`3.doInBackground(Params...) to finish the task as early as possible.

[Android Documentation]