A great variety of timer in Android

README.md

Introduction

Here are three ways to code a timer in Android.
There are three ways to achieve a timer.

1. Timer
2. Handler
3. Countdown Timer

countdown_timer.java

private static final int COUNTDOWN_TIME = 3 * 1000;
private static final int COUNTDOWN_INTERVAL = 1 * 1000;
public CountDownTimer countDownTimer = null;

countDownTimer = new CountDownTimer(COUNTDOWN_TIME, COUNTDOWN_INTERVAL)
{
    @Override
    public void onTick(long millisUntilFinished)
    {
        // Each of second.
    }

    @Override
    public void onFinish()
    {
        // This timer is time over.
        // **Implement your action.
    }
};

countDownTimer.start();
countDownTimer.cancel();

handler_timer.java

private Handler handler = new Handler();

private Runnable runnable = new Runnable()
{
    public void run()
    {
        // **Implement your action.
        handler.postDelayed(this, 1000);
        // postDelayed(this, 1000) means put a Runnable object in the main thread.
    }
};

handler.postDelayed(runnable, 1000);  // Start the timer.
handler.removeCallbacks(runnable);  // Stop the timer

timer.java

Timer timer = new Timer();

TimerTask task = new TimerTask()
{
    public void run ()
    {
        Message message = new Message();
        message.what = 1;
        handler.sendMessage(message);
    }
};

final Handler handler = new Handler()
{
    public void handleMessage(Message msg)
    {
        switch (msg.what)
        {
            case 1:
                // **Implement your action.
                break;
        }
        super.handleMessage(msg);
    }
};

protected void onDestroy ()
{
    if (timer != null)
    {
        timer.cancel();
        timer = null;
    }
    super.onDestroy();
}

protected void onCreate (Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.main);
    // timer.schedule(task, 5000) means just execute once time only.
    // timer.schedule(task, 1000, 5000) means starting this timer and repeat in a sec.
    timer.schedule(task, 1000, 5000);
}