import android.os.Handler;

import android.os.Looper;

import android.os.Message;

/**

 * This class handles regularly calling a specified runnable

 * on the looper provided in the constructor. The first call

 * occurs without delay (though still via the looper), all

 * following calls are delayed by (approximately) the interval.

 * The interval can be changed at any time, which will cause

 * an immediate execution of the runnable again.

 */

public class TickHandler extends Handler {

	private final Runnable callback;

	private int messageId;

	private long interval;

	private boolean running;

	public TickHandler(Looper looper, long interval, Runnable callback) {

		super(looper);

		this.callback = callback;

		this.interval = interval;

	}

	public synchronized void stop() {

		messageId++;

		running = false;

	}

	public synchronized void start() {

		messageId++;

		sendMessage(obtainMessage(messageId));

		running = true;

	}

	public synchronized void setInterval(long interval) {

		this.interval = interval;

		if(running) {

			start();

		}

	}

	@Override

	public synchronized void handleMessage(Message msg) {

		if(msg.what == messageId) {

			callback.run();

		}

		if(msg.what == messageId) {

			sendMessageDelayed(obtainMessage(messageId), interval);

		}

	}

}