How to check if player is re-entering the same trigger?

Question

Good day everybody!

I have a question about the correct logic for the next trigger:

In case A (image below):

The trigger in the scene is enabling light each time the player enters the trigger. There're several triggers and they all do the same - enable light when OnTriggerEnter() is called.

In case B:

This is a bug that I have: the trigger enables light each time the player enters the trigger, BUT when the player decides to go back and re-enter the same trigger the NEXT light would be enabled and I don't want that.

The light is enabled by order. Each time a method is called the NEXT light is enabled. Very fast I get "index out of range" error.

alt text

How can I tell the script to only execute the function once if the the same trigger has been re-entered?

Thank you!

Answer 1

Answer by Jack-Mariani · May 28, 2019 at 07:21 AM

You can use a bool to check if the trigger was already activated.

Like this:

 public class TriggerOnce : MonoBehaviour
 {
     private bool _triggeredAlready = false;
 
     private void OnTriggerEnter(Collider other)
     {
         //ignore if already triggered
         if(_triggeredAlready) return;
         //check if the other is the player, with a tag or as you prefer
         if (other.gameObject.CompareTag("Player"))
         {
             //confirm the trigger
             _triggeredAlready = true;
             //do your logic
             ...
         }
     }
 }

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Answer 2

Answer by Darioszka · May 28, 2019 at 07:34 AM

I would check the bool variable. Unless it's not enough in your project.

 private bool isLightOn = false;
  private void OnTriggerEnter2D(Collider2D other)
 {
        if (isLightOn)
         {
             return;
         }
 isLightOn = true;

  //enable light
 }

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Answer 3

Answer by cs120319992 · May 28, 2019 at 01:52 PM

 List<GameObject> enteredTriggers = new List<GameObject>();
 
 private void OnTriggerEnter2D(Collider2D col) {
 for(int i = 0; i < enteredTriggers.Count; i++) {
 if(col.gameObject == enteredTriggers) {
 // second time entered
 return;
 }
 
 // if not entered 
 // blablabla
 enteredTriggers.Add(col.gameObject);
 }
 }

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Answer 4

Answer by Eco-Editor · Jun 02, 2019 at 11:35 AM

Hello @cs120319992 The approach seems correct but I cannot enter the for loop. Also I've added the [i] to the count of the gameobjects:

      List<GameObject> enteredTriggers = new List<GameObject>();
      
      private void OnTriggerEnter2D(Collider2D col) {
      for(int i = 0; i < enteredTriggers.Count; i++) {
      if(col.gameObject == enteredTriggers[i]) {
      // second time entered
      return;
      }
      
      // if not entered 
      // blablabla
      enteredTriggers.Add(col.gameObject);
      }
      }

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Eco-Editor · Jun 02, 2019 at 12:14 PM 0

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$$anonymous$$y fix:

      if (other.gameObject.CompareTag("Gate"))
                 {
                     if (enteredTriggers.Contains(other.gameObject))
                     {
         //Do something
                         return;
                     }
                     else
                     {
                         enteredTriggers.Add(other.gameObject);
         //and do somethign as well
                     }
                 }

How to check if player is re-entering the same trigger?

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