Android的 - 控制与定时器和TimerTask任务？ [英] Android - Controlling a task with Timer and TimerTask?

问题描述

目前我正在试图建立一个无线扫描在我的Andr​​oid应用程序，扫描每30秒的WiFi接入点。

I am currently trying to set up a WiFi Scan in my Android application that scans for WiFi access points every 30 seconds.

我已经使用Timer和TimerTask来获得，在我需要的时间间隔运行正常扫描。

I have used Timer and TimerTask to get the scan running correctly at the intervals which I require.

不过，我希望能够停止和启动，当用户presses一键扫描和我目前遇到问题停止，然后重新启动定时器和TimerTask。

However I want to be able to stop and start the scanning when the user presses a button and I am currently having trouble stopping and then restarting the Timer and TimerTask.

下面是我的code

TimerTask scanTask;
final Handler handler = new Handler();
Timer t = new Timer();

public void doWifiScan(){

scanTask = new TimerTask() {
        public void run() {
                handler.post(new Runnable() {
                        public void run() {
                         wifiManager.scan(context); 
                         Log.d("TIMER", "Timer set off");
                        }
               });
        }};


    t.schedule(scanTask, 300, 30000); 

 }

  public void stopScan(){

   if(scanTask!=null){
      Log.d("TIMER", "timer canceled");
      scanTask.cancel();
 }

}

因此​​，定时器和任务启动精细扫描发生每隔30秒，但是我不能让它停下来，我可以停止定时器但任务仍然出现和scanTask.cancel（）似乎并没有擦出火花。

So the Timer and Task start fine and the scan happens every 30 seconds however I cant get it to stop, I can stop the Timer but the task still occurs and scanTask.cancel() doesn't seem to work either.

有没有更好的方式来做到这一点？还是我失去了一些东西，在定时器/ TimerTask的班？

Is there a better way to do this? Or am I missing something in the Timer/TimerTask classes?

推荐答案

您可能会考虑：

• 从调用取消检查布尔结果（）你的任务，因为它应该指出，如果你的要求是成功还是失败
• 尝试清除（）或取消（）在定时器而不是在的TimerTask

• Examining the boolean result from calling cancel() on your task, as it should indicate if your request succeeds or fails
• Try purge() or cancel() on the Timer instead of the TimerTask

如果你并不一定需要定时器和的TimerTask ，你可以随时使用 postDelayed （）（可在处理器和任何查看）。这将安排的Runnable 延迟一段时间后在UI线程上执行。拥有它再次出现，只要有它做你的工作定期位后，再次安排本身。然后，您可以监视一个布尔标志，表示当这个过程应该结束。例如：

If you do not necessarily need Timer and TimerTask, you can always use postDelayed() (available on Handler and on any View). This will schedule a Runnable to be executed on the UI thread after a delay. To have it recur, simply have it schedule itself again after doing your periodic bit of work. You can then monitor a boolean flag to indicate when this process should end. For example:

private Runnable onEverySecond=new Runnable() {
    public void run() {
        // do real work here

        if (!isPaused) {
            someLikelyWidget.postDelayed(onEverySecond, 1000);
        }
    }
};

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