Check if a listener has already been added to a button?

Question

I've run into a bit of a snag with creating a button in the editor.

I need to dynamically add listeners to my button, but it just keeps adding the same 3 listeners over and over because there is nothing stopping it from adding the same ones on each Awake.

alt text

Here is my code...

         var button = gameObject.GetComponent<Button>();
             
         if (receiver1 != null)
         {
             var go1 = receiver1;
             UnityAction<GameObject> action1 = new UnityAction<GameObject>(this.OnClickEvent1);
              UnityEventTools.AddObjectPersistentListener<GameObject>(button.onClick, action1, go1);            
         }
             
         if (receiver2 != null)
         {
             var go2 = receiver2;
             UnityAction<GameObject> action2 = new UnityAction<GameObject>(this.OnClickEvent2);
              UnityEventTools.AddObjectPersistentListener<GameObject>(button.onClick, action2, go2);            
         }
             
         if (receiver3 != null)
         {
             var go3 = receiver3;
             UnityAction<GameObject> action3 = new UnityAction<GameObject>(this.OnClickEvent3);
              UnityEventTools.AddObjectPersistentListener<GameObject>(button.onClick, action3, go3);           
         }

Any help is appreciated!

Answer 1

Best Answer

Answer by mchts · Apr 30, 2019 at 03:00 PM

Define your button, action1, action2 and action3 globally and move all of your add listener methods inside OnEnable() method (instead of Awake). And then add these lines to your script :

 void OnDisable(){
     UnityEventTools.RemovePersistentListener(button.onClick, action1);
     UnityEventTools.RemovePersistentListener(button.onClick, action2);
     UnityEventTools.RemovePersistentListener(button.onClick, action3);
 }

Now your listeners will be removed every time your scripts done playing!

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GeoffreyFreudenberg · Apr 30, 2019 at 10:30 PM 0

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Thank you very much! :)

mchts GeoffreyFreudenberg · May 01, 2019 at 08:27 PM 0

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You're welcome

Answer 2

Answer by x1alphaz1 · Feb 26 at 07:01 AM

this code with give u the number of listerners added

 Button btn;
 Debug.log(btn.onClick.GetPersistentEventCount());

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Check if a listener has already been added to a button?

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