延时操作，轮训，倒计时，定时等操作说明

1、CountDownTimer  

         CountDownTimer countDownTimer =newCountDownTimer(30000, 1000) {

                                                  // 30000(30秒)倒计时，每1000(1秒)调用一下onTick();

                 @Override

                 public void onTick( long millisUntilFinished) {

                     System. out.println( "到结束还剩下:" + millisUntilFinished);

                }

                 @Override

                 public void onFinish() {

                      long time = System. currentTimeMillis() - currentTimeMillis;

                     System. out.println( "已结束:用时=" + time);

                }

           };

           countDownTimer.start(); // 开始执行

           countDownTimer.cancel(); // 取消

2、Timer和TimerTask

           Timer timer = new Timer();

           TimerTask timerTask = new TimerTask() {

                 @Override

                 public void run() {

                }

           };

            // 常用于轮询

           timer .schedule(timerTask , 5000, 2000);// 5000(5秒)后，开始执行第一次run方法，此后每隔2000秒调用一次

            // 常用于延迟操作

           timer.schedule( timerTask, 5000);// 5000(5秒)后，只开始执行一次run方法

            // 取消定时

           timer.cancel();

            // 清理

           timer.purge();

            // 取消任务

            timerTask.cancel();

            // 任务已执行的时间

            timerTask.scheduledExecutionTime();

3、Handler

            //不会阻塞主线程

            handler = new Handler() {

                 @Override

                 public void handleMessag e(Message msg) {

                      super.handleMessage(msg);

                      switch (msg. what) {

                      case 0:

                            // 执行的方法

                           execute();

                            handler.sendEmptyMessageDelayed(0, 1000);// 执行时间间隔

                            break;

                     }

                }

                 // 执行的方法

                 private void execute() {

                }

           };

            handler.sendEmptyMessageDelayed(0, 30000); // 延迟多长时间执行

4、view.postDelayed

           View view = null;

           view.postDelayed(new Runnable() {

                 @Override

                 public void run() {

                }

           }, 10000);