How to Stop Timer Android

问题

following is my code:

In MainActivity.class

private OnCheckedChangeListener alert_on_off_listener = new OnCheckedChangeListener(){
    public void onCheckedChanged(RadioGroup groupname, int CheckedButtonId) {

         if(CheckedButtonId==R.id.radiobutton_on){
             Toast.makeText(getApplicationContext(), "radio on", Toast.LENGTH_LONG).show();
             alert_on = true;
             display_alert();    
         }
         else{
             alert_on = false;
         }   
    }
};

public void display_alert(){

    int delay = 10000;  
    Timer timer =new Timer();
    timer.scheduleAtFixedRate(new TimerTask()
    {
        public void run() 
            {
                Intent myIntent = new Intent(HoraWatchActivity.this,MyService.class);
                startService(myIntent);
            }
    }, delay,10000);
}

MyService.class

@Override
public void onStart(Intent intent, int startId) {
    super.onStart(intent, startId);
    if(MainActivity.alert_on)
       Toast.makeText(getApplicationContext(), "Alert is On", Toast.LENGTH_LONG).show();
    else
       Toast.makeText(getApplicationContext(), "Alert is Off",Toast.LENGTH_LONG).show();
}

I am checking the onCheckedChangeListener and calling display_alert function according to the checked radio button.

In display_alert function I was using timer scheduling at fixed rate of 10 seconds and calling myservice class.

So once I checked the radio_on button, it calls my display_alert function and got the "alert on" in toast. So its working fine.

If I again check radio_off button and then check the radio_on button, I am getting the "alert on" toast, but the toast is coming twice. Similarly if I again select the radio_on button, the toast is displaying for the third time, but I need only once. This was due to that the timer is running for every 10 seconds. I want to stop the timer once I click the radio_off button.

The problem is, once I started the timer, I was not stopping it further. When and how shall I cancel the timer tasks in my class?

回答1:

First, create your TimerTask on a separate way:

class MyTimerTask extends TimerTask {
  public void run() {
    Intent myIntent = new Intent(HoraWatchActivity.this,MyService.class);
    startService(myIntent);
  }
}

Declare it somewhere, of course visible to your OnCheckedChangeListener:

MyTimerTask myTimerTask;

Schedule it:

public void display_alert() {
  int delay = 10000;  
  myTimerTask = new MyTimerTask();
  Timer timer = new Timer();
  timer.scheduleAtFixedRate(myTimerTask, delay, 10000);
}

And then modify your code to:

private OnCheckedChangeListener alert_on_off_listener = new OnCheckedChangeListener(){
public void onCheckedChanged(RadioGroup groupname, int CheckedButtonId) {

     if(CheckedButtonId==R.id.radiobutton_on){
         Toast.makeText(getApplicationContext(), "radio on", Toast.LENGTH_LONG).show();
         alert_on = true;
         display_alert();    
     }
     else{
         myTimerTask.cancel();
         alert_on = false;
     }   
}
};

回答2:

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

you can use the code to stop/cancel timer

回答3:

First create a class extends TimerTask, make object of it and handle the operation on that object.

int delay = 10000;  
Timer timer =new Timer();
myTimer mTask= new myTimer();
timer.scheduleAtFixedRate(mTask, delay, 10000);

public class myTimer extends TimerTask
{
    @Override
    public void run() {
        Intent myIntent = new Intent(HoraWatchActivity.this,MyService.class);
            startService(myIntent);         
    }
}

when your mTask works get over just

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

thats it.

回答4:

I am able to stop a timer and a task using following code:

    if(null != timer)
    {

        timer.cancel();
        Log.i(LOG_TAG,"Number of cancelled tasks purged: " + timer.purge());
        timer = null;
    }

    if(task != null)
    {
        Log.i(LOG_TAG,"Tracking cancellation status: " + task.cancel());
        task = null;
    }

来源：https://stackoverflow.com/questions/10311087/how-to-stop-timer-android