如果有人感兴趣，我开始尝试创建一个标准对象来运行在活动UI线程上。好像还行。欢迎评论。我想这是可用的布局设计器作为一个组件拖到一个活动。真不敢相信这样的东西竟然不存在。

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，我有这样的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();
}

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);

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

    }
};
}

如果你只是想安排一个倒计时，直到将来的某个时间，并在此过程中定期通知，你可以使用从API级别1开始可用的CountDownTimer类。

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

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

你也可以使用动画器:

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();

我很惊讶，没有答案会提到RxJava2的解决方案。它真的很简单，提供了一个简单的方法来设置计时器在Android。

首先你需要设置Gradle依赖，如果你还没有这样做:

implementation "io.reactivex.rxjava2:rxjava:2.x.y"

(将x和y替换为当前版本号)

因为我们只有一个简单的，非重复的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...
        });

对于重复TASK，你可以用类似的方式使用Observable:

Observable.interval(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，. observveon (AndroidSchedulers.mainThread())意味着我们在计时器结束后运行的代码将在主线程上完成。

为了避免不必要的内存泄漏，您应该确保在Activity/Fragment被销毁时取消订阅。