How to check if handler has callback

Question

In my Application I have created a dialog on a button click and started handler on dialog creation now I want to remove handler's callbacks after dialog dismissed and on activity so I have created a handler on oncreate method of activity which continously checks for flag that I set true when dialog dismisses and when flag become true handler's callback should be removed but handler's callbacks are not removed.

final Handler handler_Alerts = new Handler();
    Runnable r_Alerts = new Runnable() {
    public void run() {
       if(Flag){
            handler1.removeCallbacks(rhandler1);
           }
  Toast.makeText(getApplicationContext(), "In Handler", Toast.LENGTH_SHORT).show();
    handler_Alerts.postDelayed(this, 1000);
                  }
        };

    handler_Alerts.postDelayed(r_Alerts, 1000);

Answer 1

There is no way to check if it has a particula runnable. You can call

handler_Alerts.removeCallbacks(r_Alerts); 

to remove any instance of r_Alerts inside the Handler queue, or

handler_Alerts.removeCallbacks(null);

to remove all the runnable in its queue

Answer 2

Do not have the reputation to comment, but Blackbelt's:

handler_Alerts.removeCallbacks(null);

should not work according to developer website, since the passed Runnable cannot be null. Instead call:

handler_Alerts.removeCallbacksAndMessages(null);

to remove all callbacks and messages.