android thread: how worker thread send signal to main(GUI) thread?

Question

I have a gui thread starting a new thread to do some busy things. The GUI thread will wait the worker thread to be completed, in the mean time the GUI need to be responsive.

Psedo code:

main thread:

start_thread(); wait_thread_done();

work thread:

doing_sth(); notify_main_thread();

What is the easiest way to do this in android?

Answer 1

The easiest way to do this is with Android's AsyncTask. The documentation is here http://developer.android.com/reference/android/os/AsyncTask.html

And you can call Activity.runOnUiThread() to update the UI from your background task.

Answer 2

A small working snippet :

new Thread() {

                    public void run() {
                            handler.post(new Runnable() {
                                public void run() {
                                    try{
                                        // **Do the GUI work here**

                                } catch (Exception e) { }
                        }});
                            };

            }.start();

Answer 3

Call Activity#runOnUiThread(Runnable), the Runnable you pass to that method will execute on the GUI thread.

Or use an AsyncTask - which is the proper way to do it.

Answer 4

waiting for result will make gui thread unresponsive. you need to use AsyncTask and override onPostExecute to perform operation required when background thread is done