Android时间倒计时的简单实线

 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.textview);
        new CountDownTimer(30000,1000){
            @Override
            public void onTick(long millisUntilFinished) {
                tv.setText("时间剩余"+":"+ millisUntilFinished / 1000);
            }
            @Override
            public void onFinish() {
                tv.setText("done!");
            }
        }.start();
    }

主要的是应用到了android里面的 CountDownTimer这个重要的API