Start Async Task within a worker thread

Question

I have two questions:

• Can we start/execute an Async Task within a worker thread?
• If yes, the methods onPreExecute(), onProgressUpdate(Progress...) and onPostExecute(Result) are invoked on the UI thread?

I wanna know that because I have a TCP connection running on a worker thread and when a packet is received I wanna start a new thread to make the parse of this packet and after that refresh some data structures on the UI thread.

Thanks in advance!

Answer 1

From the Android AsyncTask doc:

"The task instance must be created on the UI thread.", and

"execute(Params...) must be invoked on the UI thread."

So I think the answer to your first question is "no". As far as the second, those methods are all invoked on the UI thread, but it's a bit moot.

EDIT: I'm not sure if those are absolute restrictions, or strong suggestions, but in both cases, I'd recommend following them.

Answer 2

Just for the Record: If you start a AsyncTask outside the UI-Thread the onPreExecute will not be executed from the UI-Thread (but from the caller Thread). This will lead to an exception. However the onPostExecute Method will always be executed on the UI-Thread. Hope to help someone :)