// the count down timer


 new  CountDownTimer(30000, 1000)
         {
        @Override
        public void onTick(long l) {

        }
        @Override
        public void onFinish() {
        
                //on finish the count down timer finsih        
                         }
          
            }
        }

    }.start();

只需通过传递秒和textview对象调用下面的函数

public void reverseTimer(int Seconds,final TextView tv){

    new CountDownTimer(Seconds* 1000+1000, 1000) {

        public void onTick(long millisUntilFinished) {
            int seconds = (int) (millisUntilFinished / 1000);
            int minutes = seconds / 60;
            seconds = seconds % 60;
            tv.setText("TIME : " + String.format("%02d", minutes)
                    + ":" + String.format("%02d", seconds));
        }

        public void onFinish() {
            tv.setText("Completed");
        }
    }.start();
}

使用芬兰湾的科特林:

var timer = object: CountDownTimer(30000, 1000) {
        override fun onTick(millisUntilFinished: Long) {
            tvTimer.setText("seconds remaining: " + millisUntilFinished / 1000)
        }

        override fun onFinish() {
            tvTimer.setText("done!")
        }
    }
timer.start()

public class Scan extends AppCompatActivity {
int minute;
long min;
TextView tv_timer;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_scan2);
    tv_timer=findViewById(R.id.tv_timer);
    minute=Integer.parseInt("Your time in string form like 10");
    min= minute*60*1000;
    counter(min);
}
private void counter(long min) {
    CountDownTimer timer = new CountDownTimer(min, 1000) {
        public void onTick(long millisUntilFinished) {
            int seconds = (int) (millisUntilFinished / 1000) % 60;
            int minutes = (int) ((millisUntilFinished / (1000 * 60)) % 60);
            int hours = (int) ((millisUntilFinished / (1000 * 60 * 60)) % 24);
            tv_timer.setText(String.format("%d:%d:%d", hours, minutes, seconds));
        }
        public void onFinish() {
            Toast.makeText(getApplicationContext(), "Your time has been completed",
                    Toast.LENGTH_LONG).show();
        }
    };
    timer.start();
}

}

// the count down timer


 new  CountDownTimer(30000, 1000)
         {
        @Override
        public void onTick(long l) {

        }
        @Override
        public void onFinish() {
        
                //on finish the count down timer finsih        
                         }
          
            }
        }

    }.start();

我用kotlin流实现了一个很酷的定时器方法，所以你可以在ViewModel中实现它

    var countDownInit = 30
    fun countDownTimer() = flow<Int> {
    var time = countDownInit
    emit(time)
    while (true){
        time--
        delay(1000L)
        countDownInit = time
        emit(time)
    }
}

然后在你的activity或fragment中像这样调用这个函数

lifecycleScope.launch {
        lifecycle.repeatOnLifecycle(Lifecycle.State.STARTED){
                 viewModel.countDownTimer().collect{time->
                      //and update UI 
                     //and for the finish section you can just use this
                     this.cancel()          
                 }
        }
}

现在在应用程序生命周期的暂停阶段会出现崩溃，你总是有最新的时间