Here gives the very basic handler idea for communicating between the main thread and others

[Android] Handler (Simple)

// Handler is used to send/receive and operate for the messages
// Usually a new thread will be created to do something logic instead in the current main thread
// Handler will act as the postman between the main thread and separated thread


android.os.Handler.Handler
android.os.Message
java.lang.Thread


// declare a message handler to handle the receiving messages
Handler msgHandler = new Handler() {
	// to override the handleMessage method
	public void handleMessage(Message msg) {
		switch (msg.what) {
		case 1:
			break;
		case 2:
			break;
		default:
			break;
		}
	}
};

// in other new thread
new Thread() {
	@Override
	public void run() {
		// do some logic
		int what = 1;
		msgHandler.sendMessage(msgHandler.obtainMessage(what));
	}
};