Message queue in android

If you want to receive messages on a thread you should run a Looper and create a message Handler bound to this looper. The UI thread has a looper by default. There's a convenient class for creating threads with loopers called HandlerThread. Here's a good article about Handlers and Loopers: Android Guts: Intro to Loopers and Handlers.

EDIT:

HandlerThread thread = new HandlerThread("Thread name");
thread.start();

Looper looper = thread.getLooper();
Handler handler = new Handler(looper) {
    @Override
    public void handleMessage(Message msg) {
        switch(msg.what) {
            case SOME_MESSAGE_ID:
                // SOME_MESSAGE_ID is any int value
                // do something
                break;
            // other cases
        }
    }
};

handler.post(new Runnable() {
    @Override
    public void run() {
        // this code will be executed on the created thread
    }
});

// Handler.handleMessage() will be executed on the created thread
// after the previous Runnable is finished
handler.sendEmptyMessage(SOME_MESSAGE_ID);

not any other Thread.. you can sen it main Thread or Ui thread, using Handler..

create handler and send a runnable object as anarguement..

When an application first starts on a device

private final Handler handler = new Handler(Looper.getMainLooper()) {
    @Override
    public void handleMessage(Message msg) {
        if (WHAT == msg.what) {
            textView.setMaxLines(msg.arg1);
            textView.invalidate();
        } else if (WHAT_ANIMATION_END == msg.what) {
            setExpandState(msg.arg1);
        } else if (WHAT_EXPAND_ONLY == msg.what) {
            changeExpandState(msg.arg1);
        }
        super.handleMessage(msg);

    }
};

You can use various technique to create a thread in android.

private void doAnimation(final int startIndex, final int endIndex, final int what) {

    thread = new Thread(new Runnable() {

        @Override public void run() {

            if (startIndex < endIndex) {
                // if start index smaller than end index ,do expand action
                int count = startIndex;
                while (count++ < endIndex) {
                    Message msg = handler.obtainMessage(WHAT, count, 0);

                    try {
                        Thread.sleep(sleepTime);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    handler.sendMessage(msg);
                }
            } else if (startIndex > endIndex) {
                // if start index bigger than end index ,do shrink action
                int count = startIndex;
                while (count-- > endIndex) {
                    Message msg = handler.obtainMessage(WHAT, count, 0);
                    try {
                        Thread.sleep(sleepTime);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    handler.sendMessage(msg);
                }
            }

            // animation end,send signal
            Message msg = handler.obtainMessage(what, endIndex, 0);
            handler.sendMessage(msg);
        }
    });

    thread.start();
}

Please note: usually prepare() and loop() are already called in the Activity, so we should perform the following check:

  if (Looper.myLooper() == null) {
  Looper.prepare();
}