void method(boolean u,int max)
{
    uu=u;
    maxi=max;
    if (uu==true)
    { 
        CountDownTimer uy = new CountDownTimer(maxi, 1000) 
  {
            public void onFinish()
            {
                text.setText("Finish"); 
            }

            @Override
            public void onTick(long l) {
                String currentTimeString=DateFormat.getTimeInstance().format(new Date());
                text.setText(currentTimeString);
            }
        }.start();
    }

    else{text.setText("Stop ");
}

这是一个定时器的简单代码:

Timer timer = new Timer();
TimerTask t = new TimerTask() {       
    @Override
    public void run() {

        System.out.println("1");
    }
};
timer.scheduleAtFixedRate(t,1000,1000);

void method(boolean u,int max)
{
    uu=u;
    maxi=max;
    if (uu==true)
    { 
        CountDownTimer uy = new CountDownTimer(maxi, 1000) 
  {
            public void onFinish()
            {
                text.setText("Finish"); 
            }

            @Override
            public void onTick(long l) {
                String currentTimeString=DateFormat.getTimeInstance().format(new Date());
                text.setText(currentTimeString);
            }
        }.start();
    }

    else{text.setText("Stop ");
}

好的，因为这还没有清除，有3个简单的方法来处理这个。 下面的示例显示了所有3种方法，底部的示例显示了我认为更可取的方法。还记得在onPause中清理你的任务，如有必要保存状态。

import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.Handler.Callback;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class main extends Activity {
    TextView text, text2, text3;
    long starttime = 0;
    //this  posts a message to the main thread from our timertask
    //and updates the textfield
   final Handler h = new Handler(new Callback() {

        @Override
        public boolean handleMessage(Message msg) {
           long millis = System.currentTimeMillis() - starttime;
           int seconds = (int) (millis / 1000);
           int minutes = seconds / 60;
           seconds     = seconds % 60;

           text.setText(String.format("%d:%02d", minutes, seconds));
            return false;
        }
    });
   //runs without timer be reposting self
   Handler h2 = new Handler();
   Runnable run = new Runnable() {

        @Override
        public void run() {
           long millis = System.currentTimeMillis() - starttime;
           int seconds = (int) (millis / 1000);
           int minutes = seconds / 60;
           seconds     = seconds % 60;

           text3.setText(String.format("%d:%02d", minutes, seconds));

           h2.postDelayed(this, 500);
        }
    };

   //tells handler to send a message
   class firstTask extends TimerTask {

        @Override
        public void run() {
            h.sendEmptyMessage(0);
        }
   };

   //tells activity to run on ui thread
   class secondTask extends TimerTask {

        @Override
        public void run() {
            main.this.runOnUiThread(new Runnable() {

                @Override
                public void run() {
                   long millis = System.currentTimeMillis() - starttime;
                   int seconds = (int) (millis / 1000);
                   int minutes = seconds / 60;
                   seconds     = seconds % 60;

                   text2.setText(String.format("%d:%02d", minutes, seconds));
                }
            });
        }
   };


   Timer timer = new Timer();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        text = (TextView)findViewById(R.id.text);
        text2 = (TextView)findViewById(R.id.text2);
        text3 = (TextView)findViewById(R.id.text3);

        Button b = (Button)findViewById(R.id.button);
        b.setText("start");
        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Button b = (Button)v;
                if(b.getText().equals("stop")){
                    timer.cancel();
                    timer.purge();
                    h2.removeCallbacks(run);
                    b.setText("start");
                }else{
                    starttime = System.currentTimeMillis();
                    timer = new Timer();
                    timer.schedule(new firstTask(), 0,500);
                    timer.schedule(new secondTask(),  0,500);
                    h2.postDelayed(run, 0);
                    b.setText("stop");
                }
            }
        });
    }

    @Override
    public void onPause() {
        super.onPause();
        timer.cancel();
        timer.purge();
        h2.removeCallbacks(run);
        Button b = (Button)findViewById(R.id.button);
        b.setText("start");
    }
}

要记住的主要事情是，UI只能从主UI线程修改，所以使用处理程序或活动。

以下是我认为最好的方法。

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class TestActivity extends Activity {

    TextView timerTextView;
    long startTime = 0;

    //runs without a timer by reposting this handler at the end of the runnable
    Handler timerHandler = new Handler();
    Runnable timerRunnable = new Runnable() {

        @Override
        public void run() {
            long millis = System.currentTimeMillis() - startTime;
            int seconds = (int) (millis / 1000);
            int minutes = seconds / 60;
            seconds = seconds % 60;

            timerTextView.setText(String.format("%d:%02d", minutes, seconds));

            timerHandler.postDelayed(this, 500);
        }
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.test_activity);

        timerTextView = (TextView) findViewById(R.id.timerTextView);

        Button b = (Button) findViewById(R.id.button);
        b.setText("start");
        b.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Button b = (Button) v;
                if (b.getText().equals("stop")) {
                    timerHandler.removeCallbacks(timerRunnable);
                    b.setText("start");
                } else {
                    startTime = System.currentTimeMillis();
                    timerHandler.postDelayed(timerRunnable, 0);
                    b.setText("stop");
                }
            }
        });
    }

  @Override
    public void onPause() {
        super.onPause();
        timerHandler.removeCallbacks(timerRunnable);
        Button b = (Button)findViewById(R.id.button);
        b.setText("start");
    }

}

对于想要在kotlin中这样做的人:

val timer = fixedRateTimer(period = 1000L) {
            val currentTime: Date = Calendar.getInstance().time
            runOnUiThread {
                tvFOO.text = currentTime.toString()
            }
        }

为了停止计时器，你可以使用这个:

timer.cancel()

这个函数有许多其他选项，请尝试一下

这里有一个简单可靠的方法…

将以下代码放入Activity中，当Activity处于“恢复”状态时，tick()方法将在UI线程中每秒调用一次。当然，您可以更改tick()方法来做您想做的事情，或者更频繁地调用它。

@Override
public void onPause() {
    _handler = null;
    super.onPause();
}

private Handler _handler;

@Override
public void onResume() {
    super.onResume();
    _handler = new Handler();
    Runnable r = new Runnable() {
        public void run() {
            if (_handler == _h0) {
                tick();
                _handler.postDelayed(this, 1000);
            }
        }

        private final Handler _h0 = _handler;
    };
    r.run();
}

private void tick() {
    System.out.println("Tick " + System.currentTimeMillis());
}

对于那些感兴趣的人来说，“_h0=_handler”代码是必要的，以避免在tick周期内暂停和恢复活动时同时运行两个计时器。