How to end AsyncTask onBackPress() and also does it still run if it isnt finished?

I use AsyncTask in several activities.

i know how to Override onBackPress().

But when an AsyncTask is running i want to give the user the ability to go back even though the asynctask开发者_如何学C is still running.

How can I do this?

Also does an asynctask still run when activity that initiated it is closed before it finishes?

AsyncTasks run on until they complete or are cancelled. So in your case (the user presses Back and you end the main activity), the AsyncTask will carry on.

If you did want to end the AsyncTask from onBackPressed, the best you can do is to call

myAsyncTask.cancel(true);

but all that does is call the task's onCancelled() which can set a cancel flag that can be checked (usually) in doInBackground() - and if it is set the task can return.

Note that using cancel(true) does not stop the task. The docs talk about "interrupting" the task for the true case, but all they mean is that onCancelled will be called while doInBackground is running - at which point the task has an opportunity to set a flag that doInBackground can inspect.

For the true case, if the task does not implement onCancelled, and/or it does not set/inspect a flag, the task will complete doInBackground, but onPostExecute(Object) is never invoked - which is equivalent to the false case.

The async task will continue to run even if your application was closed. You have to be careful with that since your task will leak your context (keep it in memory) if it has a reference to it (so the activity) as long as your task is still running. You can avoid that by referencing your activity by a WeakReference.

You can stop a running task with cancel(true). A cancel will let the task finish its doInBackground but will never call onPostExecute. You could interrupt your background routine by checking isCanceled() and so return earlier since the task was killed.

I deleted one half of my post!

I did so confuse interrupt with a thread stop! Using true will of course NOT stop the actual thread. Thanks a lot to Torid and his answer which proved me wrong! Big lesson lernt, thanks for that!