Android :: AsyncTask's Cancel Method - Possible Bug?

As far as I can tell, AsyncTask's cancel method doesn't work as advertised. I can't tell whether this is a bug, or me not understanding AsyncTask's cancel() method. I'm asking here instead of StackOverflow because I suspect it's a bug.

I understand from past discussions here that cancel() isn't meant to actually kill a thread (though the description of the mayInterruptIfRunning flag sure implies it is). But I'm also checking for isCancelled() (which is returning false), and trying to use the onCancelled callback (which isn't getting called), to no avail.

My situation is that I have a (short-running, one small network call) AsyncTask that begins in my Activity's onCreate. If the user backs out of the screen before it finishes though, I need to either cancel the AsyncTask entirely, or at least make sure its onPostExecute doesn't do any meaningful work.

In my activity's onDestroy handler, I call cancel() on the task, and then inside the task I have an onCancelled handler that sets a boolean. In my onPostExecute handler, I check isCancelled(), and I also check to see whether the boolean has been set from onCancelled, and neither are.

I'm using the debugger, and the order of operations is:

1) onDestroy(), calls task.cancel() 2) task's onPostExecute runs, isCancelled() returns false, so I have no conditional to stop the flow and that's it. onCancelled never runs.

What am I doing wrong here? I can't find any way to tell my task not to run its work in onPostExecute.