公共方法

public final void cancel ()
         取消倒計時（取消后，再次啟動會重新開始倒計時）  

public abstract void onFinish ()
         倒計時完成時被調用     

public abstract void onTick (long millisUntilFinished)
         固定間隔被調用     參數(shù) millisUntilFinished   倒計時剩余時間。

public synchronized final CountDownTimer start ()
         啟動倒計時

//十分鐘倒計時

private MyCountDownTimer timer;
private final long TIME = 600 * 1000L;
private final long INTERVAL = 1000L;
private long leftoverTime;
//十分鐘倒計時
class MyCountDownTimer extends CountDownTimer {
public MyCountDownTimer(long millisInFuture, long countDownInterval) {
super(millisInFuture, countDownInterval);
}
@Override
public void onTick(long millisUntilFinished) {
leftoverTime = millisUntilFinished / 1000;
if (leftoverTime <= 59) {
binding.tvTimeCount.setText(String.format("00:%02d", leftoverTime));
} else {
binding.tvTimeCount.setText(String.format("%02d:%02d", leftoverTime / 60, leftoverTime % 60));
}
}

@Override
public void onFinish() {
cancelTimer();
}
}
/**
* 開始倒計時
*/
private void startTimer() {
if (timer == null) {
timer = new MyCountDownTimer(TIME, INTERVAL);
}
timer.start();
}

/**
* 取消倒計時
*/
private void cancelTimer() {
if (timer != null) {
timer.cancel();
timer = null;
}
}