我有一个变量在我的代码说它是“状态”。

我想在应用程序中根据这个变量值显示一些文本。这必须在特定的时间延迟下完成。

这就像,

检查状态变量值 显示一些文本 等待10秒 检查状态变量值 显示一些文本 等待15秒

等等。时间延迟可能会有所不同,在文本显示时设置。

我试过Thread。睡眠(时间延迟),它失败。还有更好的办法吗?


当前回答

对于使用Kotlin的人来说,inazaruk的答案将不起作用,IDE将需要初始化变量,因此我们将在一个单独的方法中使用它,而不是在Runnable中使用postDelayed。

Initialize your Runnable like this : private var myRunnable = Runnable { //Do some work //Magic happens here ↓ runDelayedHandler(1000) } Initialize your runDelayedHandler method like this : private fun runDelayedHandler(timeToWait : Long) { if (!keepRunning) { //Stop your handler handler.removeCallbacksAndMessages(null) //Do something here, this acts like onHandlerStop } else { //Keep it running handler.postDelayed(myRunnable, timeToWait) } } As you can see, this approach will make you able to control the lifetime of the task, keeping track of keepRunning and changing it during the lifetime of the application will do the job for you.

其他回答

我认为新的热点是使用ScheduledThreadPoolExecutor。像这样:

private final ScheduledThreadPoolExecutor executor_ = 
        new ScheduledThreadPoolExecutor(1);
this.executor_.scheduleWithFixedDelay(new Runnable() {
@Override
public void run() {
    update();
    }
}, 0L, kPeriod, kTimeUnit);

您可以使用Handler来发布可运行的代码。这里很好地概述了这项技术:https://guides.codepath.com/android/Repeating-Periodic-Tasks

基于上面关于ScheduledThreadPoolExecutor的帖子,我提出了一个适合我的需求的实用程序(想要每3秒触发一个方法):

class MyActivity {
    private ScheduledThreadPoolExecutor mDialogDaemon;

    private void initDebugButtons() {
        Button btnSpawnDialogs = (Button)findViewById(R.id.btn_spawn_dialogs);
        btnSpawnDialogs.setVisibility(View.VISIBLE);
        btnSpawnDialogs.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                spawnDialogs();
            }
        });
    }

    private void spawnDialogs() {
        if (mDialogDaemon != null) {
            mDialogDaemon.shutdown();
            mDialogDaemon = null;
        }
        mDialogDaemon = new ScheduledThreadPoolExecutor(1);
        // This process will execute immediately, then execute every 3 seconds.
        mDialogDaemon.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        // Do something worthwhile
                    }
                });
            }
        }, 0L, 3000L, TimeUnit.MILLISECONDS);
    }
}

试试下面的例子,它可以工作!!

在onCreate()方法中使用[Handler],该方法使用postDelayed()方法,该方法会导致Runnable被添加到消息队列中,在给定的示例中,在指定的时间流逝后运行。1

参考以下代码:

public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
    //------------------
    //------------------
    android.os.Handler customHandler = new android.os.Handler();
            customHandler.postDelayed(updateTimerThread, 0);
}

private Runnable updateTimerThread = new Runnable()
{
        public void run()
        {
            //write here whaterver you want to repeat
            customHandler.postDelayed(this, 1000);
        }
};

对任何感兴趣的人来说,这里是我用inazaruk的代码创建的一个类,它创建了所需的一切(我称之为UIUpdater,因为我用它定期更新UI,但你可以叫它任何你喜欢的名字):

import android.os.Handler;
/**
 * A class used to perform periodical updates,
 * specified inside a runnable object. An update interval
 * may be specified (otherwise, the class will perform the 
 * update every 2 seconds).
 * 
 * @author Carlos Simões
 */
public class UIUpdater {
        // Create a Handler that uses the Main Looper to run in
        private Handler mHandler = new Handler(Looper.getMainLooper());

        private Runnable mStatusChecker;
        private int UPDATE_INTERVAL = 2000;

        /**
         * Creates an UIUpdater object, that can be used to
         * perform UIUpdates on a specified time interval.
         * 
         * @param uiUpdater A runnable containing the update routine.
         */
        public UIUpdater(final Runnable uiUpdater) {
            mStatusChecker = new Runnable() {
                @Override
                public void run() {
                    // Run the passed runnable
                    uiUpdater.run();
                    // Re-run it after the update interval
                    mHandler.postDelayed(this, UPDATE_INTERVAL);
                }
            };
        }

        /**
         * The same as the default constructor, but specifying the
         * intended update interval.
         * 
         * @param uiUpdater A runnable containing the update routine.
         * @param interval  The interval over which the routine
         *                  should run (milliseconds).
         */
        public UIUpdater(Runnable uiUpdater, int interval){
            UPDATE_INTERVAL = interval;
            this(uiUpdater);
        }

        /**
         * Starts the periodical update routine (mStatusChecker 
         * adds the callback to the handler).
         */
        public synchronized void startUpdates(){
            mStatusChecker.run();
        }

        /**
         * Stops the periodical update routine from running,
         * by removing the callback.
         */
        public synchronized void stopUpdates(){
            mHandler.removeCallbacks(mStatusChecker);
        }
}

然后你可以在你的类中创建一个UIUpdater对象,并像这样使用它:

...
mUIUpdater = new UIUpdater(new Runnable() {
         @Override 
         public void run() {
            // do stuff ...
         }
    });

// Start updates
mUIUpdater.startUpdates();

// Stop updates
mUIUpdater.stopUpdates();
...

如果你想使用它作为一个活动更新器,把开始调用放在onResume()方法中,停止调用放在onPause()中,这样更新就会根据活动可见性开始和停止。