Android :: How To Arrange Long (time Consuming) Actions?

For instance, we are in SomeActivity and the activity has a button that invokes moving files from one dir to another (let's call it job).On Android things change. I know there's the AsyncTask that is probably provided to solve my case. There's even a good example of how it should be used. But since there's no guarantee of how long an Activity instance will live the AsyncTask should be cancelled on onSaveInstanceState (and restarted on onRestoreInstanceState). This means using AsyncTask there's no guarantee we are able to fully fulfill the job once started. In some cases as sending an http post request for creating a user I would not want to get in "user already exists for this login" trouble on reruning the AsyncTask. This is possible since the AsyncTask can be interrupted while the request is already sent (and the server actually is doing its job - creating a new user), but the AsyncTask is canceled before we got the response.