android countdowntimer刻度不准确

Question

我正在使用倒数计时器进行音频通知...而且从一开始就不准确...

使用初始参数

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();
}

我可以在日志中看到初始倒计时正确设置为 180000，但下一个应该是 120000 并且设置为 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

这很烦人，因为音频通知器只希望说“2 分钟”而不是“1 分 59 秒”......；为什么间隔不正确......？ 我可以在将文本设置为语音字符串时尝试它...但是有什么方法可以获取正确的数据吗？

感谢建议

Answer 1

我知道这是一个老问题——但我也遇到过这个问题，我想我会分享我的解决方案。

显然 CountDownTimer 不是很准确，所以我决定使用 java.util.Timer 实现更精确的倒数计时器：

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();
}

用法示例如下：

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
    }
};

要开始倒计时，只需调用 countDown.start()。 countDown.stop() 停止 countDown，可以使用 countDown.restart() 重新启动。

希望这对将来的任何人都有帮助。

Answer 2

除了使用millisUntilFinished，您可以使用一个变量来保存剩余时间，并在每个onTick 中减去带有间隔的变量。这样remainingTime总是准确的。

private class MyTimer(
    countDownTime: Long, 
    interval: Long
) : CountDownTimer(countDownTime, interval) {

    private var remainingTime = countDownTime

    override fun onFinish() {
    }

    override fun onTick(millisUntilFinished: Long) {
        // consume remainingTime here and then minus interval
        remainingTime -= interval
    }
}

Answer 3

这是对 Noam Gal 发布的内容的扩展。我添加了额外的功能，您可以在其中暂停和恢复计时器。这对我来说很有帮助。

public abstract class PreciseCountdownTimer extends Timer {

    private long totalTime, interval, delay;
    private TimerTask task;
    private long startTime = -1;
    private long timeLeft;
    private boolean restart = false;
    private boolean wasCancelled = false;
    private boolean wasStarted = false;

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


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

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

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

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

                onTick(timeLeft);
            }
        };
    }

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

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

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

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

    public void resume(){
        wasCancelled = false;
        this.task = buildTask(timeLeft);
        this.startTime = - 1;
        start();
        onResumed();
    }

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

    public abstract void onTick(long timeLeft);

    public abstract void onFinished();

    public abstract void onPaused();

    public abstract void onResumed();
}

用法示例几乎完全相同：

this.timer = new PreciseCountdownTimer(totalTime, interval, delay) {
            @Override
            public void onTick(long timeLeft) {
                // 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
            }

            @Override
            public void onPaused() {
                // runs after the timer has been paused
            }

            @Override
            public void onResumed() {
                // runs after the timer has been resumed
            }
        };

尽情享受吧：D