Are threads reliable enough to calculate seconds?

Question

I am making an Android App that at some activity shows a timer with hours minutes and seconds. As seconds value will update every second, I was thinking to make a thread with 1000 ms sleep, after each cycle it will add 1 to seconds and update the text view. Accordingly it will calculate minutes and hours and update the respective text views.

But I have one doubt in mind, are threads reliable enough to accomplish such a task or should I use inbuilt library function to get seconds after every cycle ? I am a little concerned about getting my timer getting out of sync if I rely completely on thread to calculate time.

Answer 1

Sleep is not good enough.

Sleep will pause the thread for a minimum of the specified period of time, but the actual sleep period may be longer than the specified time.

Answer 2

Use Handler. Here's a very good detailed post on that.

long startTime = 0;

Handler timerHandler = new Handler();

Runnable timerRunnable = new Runnable() {
    @Override
    public void run() {
        long millis = System.currentTimeMillis() - startTime;
        int seconds = (int) Math.round(diff / ((double)1000));
        int minutes = (int) Math.round(seconds / ((double)60));
        seconds = seconds % 60;

        // Use the seconds

        timerHandler.postDelayed(this, 500);
    }
};

Start timer-

startTime = System.currentTimeMillis();
timerHandler.postDelayed(timerRunnable, 0);

Stop timer-

timerHandler.removeCallbacks(timerRunnable);

On pause-

timerHandler.removeCallbacks(timerRunnable);

Answer 3

Sleep with 1000 ms delay is bad option, since there is always a jitter and also some CPU time is spent on execution of your routine.

I would propose to profit from ScheduledExecutorService.scheduleAtFixedRate method, that will call your implementation at fixed rate.