Android计时器？如何？-Java 学习之路

283

有人可以给出一个每秒钟更新文本字段的简单示例吗？

我想做一个飞球，需要每秒计算/更新球坐标，这就是为什么我需要某种计时器 .

我从here得不到任何东西 .

18 回答

他是一个更简单的解决方案，在我的应用程序中运行良好 .

public class MyActivity extends Acitivity {

    TextView myTextView;
    boolean someCondition=true;

     @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.my_activity);

            myTextView = (TextView) findViewById(R.id.refreshing_field);

            //starting our task which update textview every 1000 ms
            new RefreshTask().execute();



        }

    //class which updates our textview every second

    class RefreshTask extends AsyncTask {

            @Override
            protected void onProgressUpdate(Object... values) {
                super.onProgressUpdate(values);
                String text = String.valueOf(System.currentTimeMillis());
                myTextView.setText(text);

            }

            @Override
            protected Object doInBackground(Object... params) {
                while(someCondition) {
                    try {
                        //sleep for 1s in background...
                        Thread.sleep(1000);
                        //and update textview in ui thread
                        publishProgress();
                    } catch (InterruptedException e) {
                        e.printStackTrace(); 

                };
                return null;
            }
        }
    }

回复于 2024-04-29T18:26:23+08:00

如果您还需要在UI线程上运行代码（而不是在计时器线程上），请查看博客：http://steve.odyfamily.com/?p=12

public class myActivity extends Activity {
private Timer myTimer;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.main);

    myTimer = new Timer();
    myTimer.schedule(new TimerTask() {          
        @Override
        public void run() {
            TimerMethod();
        }

    }, 0, 1000);
}

private void TimerMethod()
{
    //This method is called directly by the timer
    //and runs in the same thread as the timer.

    //We call the method that will work with the UI
    //through the runOnUiThread method.
    this.runOnUiThread(Timer_Tick);
}


private Runnable Timer_Tick = new Runnable() {
    public void run() {

    //This method runs in the same thread as the UI.               

    //Do something to the UI thread here

    }
};
}

回复于 2024-04-29T18:26:23+08:00

如果有人感兴趣，我开始玩创建一个在活动UI线程上运行的标准对象 . 似乎工作正常 . 欢迎评论 . 我希望布局设计器可以将其作为拖动到Activity的组件 . 不敢相信这样的东西还不存在 .

package com.example.util.timer;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;

public class ActivityTimer {

    private Activity m_Activity;
    private boolean m_Enabled;
    private Timer m_Timer;
    private long m_Delay;
    private long m_Period;
    private ActivityTimerListener m_Listener;
    private ActivityTimer _self;
    private boolean m_FireOnce;

    public ActivityTimer() {
        m_Delay = 0;
        m_Period = 100;
        m_Listener = null;
        m_FireOnce = false;
        _self = this;
    }

    public boolean isEnabled() {
        return m_Enabled;
    }

    public void setEnabled(boolean enabled) {
        if (m_Enabled == enabled)
            return;

        // Disable any existing timer before we enable a new one
        Disable();

        if (enabled) {
            Enable();
        }
    }

    private void Enable() {
        if (m_Enabled)
            return;

        m_Enabled = true;

        m_Timer = new Timer();
        if (m_FireOnce) {
            m_Timer.schedule(new TimerTask() {
                @Override
                public void run() {
                    OnTick();
                }
            }, m_Delay);
        } else {
            m_Timer.schedule(new TimerTask() {
                @Override
                public void run() {
                    OnTick();
                }
            }, m_Delay, m_Period);
        }
    }

    private void Disable() {
        if (!m_Enabled)
            return;

        m_Enabled = false;

        if (m_Timer == null)
            return;

        m_Timer.cancel();
        m_Timer.purge();
        m_Timer = null;
    }

    private void OnTick() {
        if (m_Activity != null && m_Listener != null) {
            m_Activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    m_Listener.OnTimerTick(m_Activity, _self);
                }
            });
        }
        if (m_FireOnce)
            Disable();
    }

    public long getDelay() {
        return m_Delay;
    }

    public void setDelay(long delay) {
        m_Delay = delay;
    }

    public long getPeriod() {
        return m_Period;
    }

    public void setPeriod(long period) {
        if (m_Period == period)
            return;
        m_Period = period;
    }

    public Activity getActivity() {
        return m_Activity;
    }

    public void setActivity(Activity activity) {
        if (m_Activity == activity)
            return;
        m_Activity = activity;
    }

    public ActivityTimerListener getActionListener() {
        return m_Listener;
    }

    public void setActionListener(ActivityTimerListener listener) {
        m_Listener = listener;
    }

    public void start() {
        if (m_Enabled)
            return;
        Enable();
    }

    public boolean isFireOnlyOnce() {
        return m_FireOnce;
    }

    public void setFireOnlyOnce(boolean fireOnce) {
        m_FireOnce = fireOnce;
    }
}

在活动中，我有这个onStart：

@Override
protected void onStart() {
    super.onStart();

    m_Timer = new ActivityTimer();
    m_Timer.setFireOnlyOnce(true);
    m_Timer.setActivity(this);
    m_Timer.setActionListener(this);
    m_Timer.setDelay(3000);
    m_Timer.start();
}

回复于 2024-04-29T18:26:23+08:00

1

您需要创建一个线程来处理更新循环并使用它来更新textarea . 但棘手的部分是只有主线程才能实际修改ui，因此更新循环线程需要通知主线程进行更新 . 这是使用Handler完成的 .

看看这个链接：http://developer.android.com/guide/topics/ui/dialogs.html#点击 Headers 为"Example ProgressDialog with a second thread"的部分 . 这是您需要做的一个示例，除了使用进度对话框而不是文本字段 .

回复于 2024-04-29T18:26:23+08:00
0

您希望UI更新发生在已存在的UI线程中 .

最好的方法是使用一个Handler，它使用postDelayed在延迟后运行Runnable（每次运行安排下一个）;使用removeCallbacks清除回调 .

你_____1859_ t你想要什么 . （另见Updating the UI from a Timer的相同文章） .

回复于 2024-04-29T18:26:23+08:00

如果你已经有增量时间了 .

public class Timer {
    private float lastFrameChanged;
    private float frameDuration;
    private Runnable r;

    public Timer(float frameDuration, Runnable r) {
        this.frameDuration = frameDuration;
        this.lastFrameChanged = 0;
        this.r = r;
    }

    public void update(float dt) {
        lastFrameChanged += dt;

        if (lastFrameChanged > frameDuration) {
            lastFrameChanged = 0;
            r.run();
        }
    }
}

回复于 2024-04-29T18:26:23+08:00

对于那些不能依赖Chronometer的人，我提出了一个实用类，其中一个建议是：

public class TimerTextHelper implements Runnable {
   private final Handler handler = new Handler();
   private final TextView textView;
   private volatile long startTime;
   private volatile long elapsedTime;

   public TimerTextHelper(TextView textView) {
       this.textView = textView;
   }

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

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

       if (elapsedTime == -1) {
           handler.postDelayed(this, 500);
       }
   }

   public void start() {
       this.startTime = System.currentTimeMillis();
       this.elapsedTime = -1;
       handler.post(this);
   }

   public void stop() {
       this.elapsedTime = System.currentTimeMillis() - startTime;
       handler.removeCallbacks(this);
   }

   public long getElapsedTime() {
       return elapsedTime;
   }

}

使用..只是做：

TimerTextHelper timerTextHelper = new TimerTextHelper(textView);
 timerTextHelper.start();

.....

timerTextHelper.stop();
 long elapsedTime = timerTextHelper.getElapsedTime();

回复于 2024-04-29T18:26:23+08:00

8
因为这个问题仍然吸引了很多谷歌搜索用户（关于Android计时器），我想插入我的两个硬币 .

首先，Timer类将在Java 9 (read the accepted answer)中弃用 .

official建议的方法是使用ScheduledThreadPoolExecutor，它更有效，功能更丰富，可以额外安排命令在给定的延迟后运行，或定期执行 . 此外，它还提供了ThreadPoolExecutor的额外灵活性和功能 .

以下是使用简单功能的示例 .
- 创建执行程序服务：
```
final ScheduledExecutorService SCHEDULER = Executors.newScheduledThreadPool(1);
```
- 安排你运行：
```
final Future<?> future = SCHEDULER.schedule(Runnable task, long delay,TimeUnit unit);
```
- 您现在可以使用 future 取消任务或检查是否已完成，例如：
```
future.isDone();
```
希望您会发现这对于在Android中创建任务非常有用 .

完整的例子：
```
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
Future<?> sampleFutureTimer = scheduler.schedule(new Runnable(), 120, TimeUnit.SECONDS);
if (sampleFutureTimer.isDone()){
    // Do something which will save world.
}
```
回复于 2024-04-29T18:26:23+08:00

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 ");
}

回复于 2024-04-29T18:26:23+08:00

421

我认为你可以用Rx方式做到：

timerSubscribe = Observable.interval(1, TimeUnit.SECONDS)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Action1<Long>() {
                @Override
                public void call(Long aLong) {
                      //TODO do your stuff
                }
            });

取消这个就像：

timerSubscribe.unsubscribe();

Rx定时器http://reactivex.io/documentation/operators/timer.html

回复于 2024-04-29T18:26:23+08:00

你也可以使用动画师：

int secondsToRun = 999;

ValueAnimator timer = ValueAnimator.ofInt(secondsToRun);
timer.setDuration(secondsToRun * 1000).setInterpolator(new LinearInterpolator());
timer.addUpdateListener(new ValueAnimator.AnimatorUpdateListener()
    {
        @Override
        public void onAnimationUpdate(ValueAnimator animation)
        {
            int elapsedSeconds = (int) animation.getAnimatedValue();
            int minutes = elapsedSeconds / 60;
            int seconds = elapsedSeconds % 60;

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

回复于 2024-04-29T18:26:23+08:00

这是一个简单可靠的方法......

将以下代码放在Activity中，当您的活动处于“恢复”状态时，将在UI线程中每秒调用tick（）方法 . 当然，您可以更改tick（）方法以执行您想要的操作，或者更频繁或更不频繁地调用 .

@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，如果您的活动暂停并在滴答期内恢复，则必须使用“_h0 = _handler”代码以避免两个定时器同时运行 .

回复于 2024-04-29T18:26:23+08:00

61
我很惊讶没有答案可以提及RxJava2的解决方案 . 它非常简单，并提供了一种在Android中设置计时器的简便方法 .

首先，您需要设置Gradle依赖项，如果您还没有这样做：
```
implementation "io.reactivex.rxjava2:rxjava:2.x.y"
```
（用current version number替换 x 和 y ）

由于我们只有一个简单的 NON-REPEATING TASK ，我们可以使用 Completable 对象：
```
Completable.timer(2, TimeUnit.SECONDS, Schedulers.computation())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(() -> {
            // Timer finished, do something...
        });
```
对于 REPEATING TASK ，您可以以类似的方式使用 Observable ：
```
Observable(2, TimeUnit.SECONDS, Schedulers.computation())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(tick -> {
            // called every 2 seconds, do something...
        }, throwable -> {
            // handle error
        });
```
Schedulers.computation() 确保我们的计时器在后台线程上运行， .observeOn(AndroidSchedulers.mainThread()) 表示我们在计时器完成后运行的代码将在主线程上完成 .

为避免不必要的内存泄漏，您应确保在销毁Activity / Fragment时取消订阅 .
回复于 2024-04-29T18:26:23+08:00

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;

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

public class MainActivity extends Activity {

 CheckBox optSingleShot;
 Button btnStart, btnCancel;
 TextView textCounter;

 Timer timer;
 MyTimerTask myTimerTask;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  optSingleShot = (CheckBox)findViewById(R.id.singleshot);
  btnStart = (Button)findViewById(R.id.start);
  btnCancel = (Button)findViewById(R.id.cancel);
  textCounter = (TextView)findViewById(R.id.counter);

  btnStart.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View arg0) {

    if(timer != null){
     timer.cancel();
    }

    //re-schedule timer here
    //otherwise, IllegalStateException of
    //"TimerTask is scheduled already" 
    //will be thrown
    timer = new Timer();
    myTimerTask = new MyTimerTask();

    if(optSingleShot.isChecked()){
     //singleshot delay 1000 ms
     timer.schedule(myTimerTask, 1000);
    }else{
     //delay 1000ms, repeat in 5000ms
     timer.schedule(myTimerTask, 1000, 5000);
    }
   }});

  btnCancel.setOnClickListener(new OnClickListener(){

   @Override
   public void onClick(View v) {
    if (timer!=null){
     timer.cancel();
     timer = null;
    }
   }
  });

 }

 class MyTimerTask extends TimerTask {

  @Override
  public void run() {
   Calendar calendar = Calendar.getInstance();
   SimpleDateFormat simpleDateFormat = 
     new SimpleDateFormat("dd:MMMM:yyyy HH:mm:ss a");
   final String strDate = simpleDateFormat.format(calendar.getTime());

   runOnUiThread(new Runnable(){

    @Override
    public void run() {
     textCounter.setText(strDate);
    }});
  }

 }

}

.XML

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".MainActivity" >

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_horizontal"
    android:autoLink="web"
    android:text="http://android-er.blogspot.com/"
    android:textStyle="bold" />
<CheckBox 
    android:id="@+id/singleshot"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Single Shot"/>

回复于 2024-04-29T18:26:23+08:00

好吧，因为这还没有解决，有3种简单的方法来处理这个问题 . 下面是一个显示所有3的示例，底部是一个示例，显示了我认为更可取的方法 . 还记得在onPause中清理你的任务，必要时保存状态 .

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activity.runOnUIThread（Runnable r）;

这是我认为首选的方法 .

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");
    }

}

回复于 2024-04-29T18:26:23+08:00

这是一个计时器的简单代码：

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

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

回复于 2024-04-29T18:26:23+08:00

0
很简单！你创建了新的计时器 .
```
Timer timer = new Timer();
```
然后扩展计时器任务
```
class UpdateBallTask extends TimerTask {
   Ball myBall;

   public void run() {
       //calculate the new position of myBall
   }
}
```
然后以一些更新间隔将新任务添加到Timer
```
final int FPS = 40;
TimerTask updateBall = new UpdateBallTask();
timer.scheduleAtFixedRate(updateBall, 0, 1000/FPS);
```
免责声明：这不是理想的解决方案 . 这是使用Timer类的解决方案（由OP提出） . 在Android SDK中，建议使用Handlerclass（在接受的答案中有例子） .
回复于 2024-04-29T18:26:23+08:00

如果一个人只想安排倒计时，直到将来有定期通知的时间段，您可以使用自API级别1以来可用的CountDownTimer类 .

new CountDownTimer(30000, 1000) {
    public void onTick(long millisUntilFinished) {
        editText.setText("Seconds remaining: " + millisUntilFinished / 1000);
    }

    public void onFinish() {
        editText.setText("Done");
    }
}.start();

回复于 2024-04-29T18:26:23+08:00

Android计时器？如何？

18 回答

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