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1. Android 秒表 Demo

代码主要从系统-时钟的秒表模块截取。

主要原理：View事件的PostRunable进行时间和UI的更新，不同于我们常用的Thread+延时， Handle + 延时和TimeTask定时，起码我第一次看还是觉得很神奇

2. GitHub demo下载

3. 源码方法

3.1 秒表开始

主要进行秒表开始和UI的状态切换，主要核心是 mTime.post(mTimeUpdateRunnable); 进行触发

/**     * Start the stopwatch.     */    public void doStart(View view) {        // Update the stopwatch state. 更新数据库状态        DataModel.getDataModel().startStopwatch();        // Start UI updates.        startUpdatingTime();        mTime.update();        mTimeText.blinkTimeStr(false);        // Acquire the wake lock.防止CPU休眠，导致不刷新时间        acquireWakeLock();    }    /**     * Post the first runnable to update times within the UI. It will reschedule     * itself as needed.     */    private void startUpdatingTime() {        // Ensure only one copy of the runnable is ever scheduled by first        // stopping updates.        stopUpdatingTime();        mTime.post(mTimeUpdateRunnable);    }

3.2 设置Runnable定时

/**     * This runnable periodically updates times throughout the UI. It stops     * these updates when the stopwatch is no longer running.     */    private final class TimeUpdateRunnable implements Runnable {
           @Override        public void run() {            Log.d("suhuazhi", "TimeUpdateRunnable");            final long startTime = SystemClock.elapsedRealtime();            updateTime();            if (getStopwatch().isRunning()) {                // The stopwatch is still running so execute this runnable again                // after a delay.                final boolean talkBackOn = true;                // Grant longer time between redraws when talk-back is on to let                // it catch up.                final int period = talkBackOn ? 500 : 25;                // Try to maintain a consistent period of time between redraws.                final long endTime = SystemClock.elapsedRealtime();                final long delay = Math.max(0, startTime + period - endTime);                mTime.postDelayed(this, delay);            }        }    }

3.3 秒表暂停

核心 自定View 进行 mTime.removeCallbacks(mTimeUpdateRunnable) 即可

/**     * Pause the stopwatch.     */    public void doPause(View view) {        // Update the stopwatch state        DataModel.getDataModel().pauseStopwatch();        // Redraw the paused stopwatch time.        updateTime();        // Stop UI updates.        stopUpdatingTime();        mTimeText.blinkTimeStr(true);    }    /**     * Remove the runnable that updates times within the UI.     */    private void stopUpdatingTime() {        mTime.removeCallbacks(mTimeUpdateRunnable);    }

3.4 秒表的复位

记得是否CPU唤醒锁，将数据库秒表数据重新初始化即可

/**     * Reset the stopwatch.     */    public void doReset(View view) {        // Update the stopwatch state.        DataModel.getDataModel().resetStopwatch();        // Clear the times.        mTimeText.setTime(0, true, true);        // Release the wake lock.        releaseWakeLock();    }

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