android countdowntimer tick is not accurate

Question

I am using a countdown timer for audio notification... and it's not accurate from the start...

using initial parameters

private final long startCountDown; 
private final long intervalCountDown;
    ...
    startCountDown = 180 * 1000;   // 3 mns  - to be set from Preferences later
intervalCountDown = 60 * 1000;   // 1 mns - to be set from Preferences later
    ...
    public void onTick(long millisUntilFinished) {
       Log.d(TAG, "notify countDown: " + millisUntilFinished + " msecs");
    }


    countDownTimer = new SwimCountDownTimer(startCountDown,intervalCountDown);
    ....

public void startCountDown() {
    Log.d(TAG, "start countDown for " + startCountDown + " msecs" );
    countDownTimer.start();
}

I can see in the log that the initial countdown is correctly set to 180000 but the next one should be 120000 and it's set to 119945 !!!

04-27 14:50:42.146: I/SWIMMER(8670): notify countDown: 180000 msecs
04-27 14:51:42.206: I/SWIMMER(8670): notify countDown: 119945 msecs

This is quite annoying as the audio notifier is expecting to say only '2 minutes" and not "1 minute and fifty nine seconds" ...; why the interval is not right ... ? I can tricj it in setting myself the text to speech string ... but is there any way to get correct data ?

thanks for suggestions

Answer 1

I know it's an old question- but I've also encountered the problem, and thought I would share my solution.

Apperantly CountDownTimer isn't very accurate, so I've decided to implement a more percise countdown timer, using java.util.Timer:

public abstract class PreciseCountdown extends Timer {
    private long totalTime, interval, delay;
    private TimerTask task;
    private long startTime = -1;
    private boolean restart = false, wasCancelled = false, wasStarted = false;

    public PreciseCountdown(long totalTime, long interval) {
        this(totalTime, interval, 0);
    }

    public PreciseCountdown(long totalTime, long interval, long delay) {
        super("PreciseCountdown", true);
        this.delay = delay;
        this.interval = interval;
        this.totalTime = totalTime;
        this.task = getTask(totalTime);
    }

    public void start() {
        wasStarted = true;
        this.scheduleAtFixedRate(task, delay, interval);
    }

    public void restart() {
        if(!wasStarted) {
            start();
        }
        else if(wasCancelled) {
            wasCancelled = false;
            this.task = getTask(totalTime);
            start();
        }
        else{
            this.restart = true;
        }
    }

    public void stop() {
        this.wasCancelled = true;
        this.task.cancel();
    }

    // Call this when there's no further use for this timer
    public void dispose(){
        cancel();
        purge();
    }

    private TimerTask getTask(final long totalTime) {
        return new TimerTask() {

            @Override
            public void run() {
                long timeLeft;
                if (startTime < 0 || restart) {
                    startTime = scheduledExecutionTime();
                    timeLeft = totalTime;
                    restart = false;
                } else {
                    timeLeft = totalTime - (scheduledExecutionTime() - startTime);

                    if (timeLeft <= 0) {
                        this.cancel();
                        startTime = -1;
                        onFinished();
                        return;
                    }
                }

                onTick(timeLeft);
            }
        };
    }

    public abstract void onTick(long timeLeft);
    public abstract void onFinished();
}

Usage example would be:

this.countDown = new PreciseCountdown(totalTime, interval, delay) {
    @Override
    public void onTick(long timeLeft) {
        // update..
        // note that this runs on a different thread, so to update any GUI components you need to use Activity.runOnUiThread()
    }

    @Override
    public void onFinished() {
        onTick(0); // when the timer finishes onTick isn't called
        // count down is finished
    }
};

to start the countdown, simply call countDown.start(). countDown.stop() stops the countDown, which could be restarted using countDown.restart().

Hope this is any help for anyone in the future.