当活动不在前面时,在Android中暂停CountDownTimer

Question

我有一个使用从10开始倒计时的CountDownTimer的活动.当活动不再处于焦点时如何暂停该计时器,如用户接到电话或其他内容,然后在用户返回时恢复计时器活动？这甚至可能吗？

Answer 1

我会在onTick处理程序中添加一些东西来保存你的类中的计时器进度(剩下的毫秒数).

在onPause()方法中为活动调用计时器上的cancel().

在活动的onResume()方法中,创建一个新的计时器,保留剩余的毫秒数.

Answer 2

您可以使用pause()暂停计时器,稍后通过调用启动或恢复countDownTimer start().

/**
 * This class uses the native CountDownTimer to 
 * create a timer which could be paused and then
 * started again from the previous point. You can 
 * provide implementation for onTick() and onFinish()
 * then use it in your projects.
 */
public abstract class CountDownTimerPausable {
    long millisInFuture = 0;
    long countDownInterval = 0;
    long millisRemaining =  0;

    CountDownTimer countDownTimer = null;

    boolean isPaused = true;

    public CountDownTimerPausable(long millisInFuture, long countDownInterval) {
        super();
        this.millisInFuture = millisInFuture;
        this.countDownInterval = countDownInterval;
        this.millisRemaining = this.millisInFuture;
    }
    private void createCountDownTimer(){
        countDownTimer = new CountDownTimer(millisRemaining,countDownInterval) {

            @Override
            public void onTick(long millisUntilFinished) {
                millisRemaining = millisUntilFinished;
                CountDownTimerPausable.this.onTick(millisUntilFinished);

            }

            @Override
            public void onFinish() {
                CountDownTimerPausable.this.onFinish();

            }
        };
    }
    /**
     * Callback fired on regular interval.
     * 
     * @param millisUntilFinished The amount of time until finished. 
     */
    public abstract void onTick(long millisUntilFinished);
    /**
     * Callback fired when the time is up. 
     */
    public abstract void onFinish();
    /**
     * Cancel the countdown.
     */
    public final void cancel(){
        if(countDownTimer!=null){
            countDownTimer.cancel();
        }
        this.millisRemaining = 0;
    }
    /**
     * Start or Resume the countdown. 
     * @return CountDownTimerPausable current instance
     */
    public synchronized final CountDownTimerPausable start(){
        if(isPaused){
            createCountDownTimer();
            countDownTimer.start();
            isPaused = false;
        }
        return this;
    }
    /**
     * Pauses the CountDownTimerPausable, so it could be resumed(start)
     * later from the same point where it was paused.
     */
    public void pause()throws IllegalStateException{
        if(isPaused==false){
            countDownTimer.cancel();
        } else{
            throw new IllegalStateException("CountDownTimerPausable is already in pause state, start counter before pausing it.");
        }
        isPaused = true;
    }
    public boolean isPaused() {
        return isPaused;
    }
}

Answer 3

无需创建新的Timer,只需设置millisUntilFinished = total即可.例如

private CountDownTimer cdTimer;
private long total = 30000;

        ...
        toggleButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view){
                if(toggleButton.isChecked()) {
                    startCountDownTimer();
                }else{
                    cdTimer.cancel();
                }
            }
        });
        ...

    private void startCountDownTimer() {
        cdTimer = new CountDownTimer(total, 1000) {
            public void onTick(long millisUntilFinished) {
                //update total with the remaining time left
                total = millisUntilFinished;
                nTimeLabel.setText("seconds remaining: " +  millisUntilFinished/ 1000);
            }
            public void onFinish() {
                nTimeLabel.setText("done!");
            }
        }.start();
    }