The problem I believe is with the heavy image download task. Even if you cancel the async task the image download will continue to execute and the async task does not finish until the download is complete. You might want to check the isCancelled() method on AyncTask while the download is going on and kill the download if the task is cancelled.
For reference, heres the documentation on cancel() method :
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 onCancelled(Object) being invoked on the UI thread after doInBackground(Object[]) returns. Calling this method guarantees that onPostExecute(Object) is never invoked. After invoking this method, you should check the value returned by isCancelled() periodically from doInBackground(Object[]) to finish the task as early as possible.
