Question about Android runnable

Question

I saw a piece of code online. I am wondering why we need to use runnable to set TextView text? Thank!

    while (true) {
    // listen for incoming clients
    Socket client = serverSocket.accept();
    handler.post(new Runnable() {
        @Override
        public void run() {
            serverStatus.setText("Connected.");
        }
    });

http://thinkandroid.wordpress.com/2010/03/27/incorporating-socket-programming-into-your-applications/

Answer 1

, ? UI - . , . , , - UI (, serverStatus), . .

. UI , . , , , Runnables.

( ), : http://developer.android.com/guide/appendix/faq/commontasks.html#threading

Answer 2

. ( edittext) Uithread. Runnable . : http://developer.android.com/reference/android/app/Activity.html#runOnUiThread(java.lang.Runnable)