Unity3D using OnTriggerStay

Question

I'm using the event OnTriggerStay2D to destroy an object, the reason i'm using this instead of OnTriggerEnter2D is because i'm dragging the object using the touchscreen, and i want to destroy it after it is released, the problem i have is that OntriggerStay2D is not always called, so sometimes the object is not destroyed after it is released and it has to be moved again to work, i've read the docummentation from Unity

OnTriggerStay is called almost all the frames for every Collider other that is touching the trigger.

public void OnTriggerStay2D(Collider2D other)
{
        if (gameObject.tag == other.tag) {

            Destroy (other.gameObject);

    }
}

I would like to know if there's any way to call OntriggerStay2D everytime i release the object. Thanks.

Edit Dragging code

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

    public class Drag : MonoBehaviour {

        private bool draggingItem = false;
        private GameObject draggedObject;
        private Vector2 touchOffset;

        void Update ()
        {
            if (HasInput)
            {
                DragOrPickUp();
            }
            else
            {
                if (draggingItem)
                    DropItem();
            }
        }

        Vector2 CurrentTouchPosition
        {
            get
            {
                Vector2 inputPos;
                inputPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
                return inputPos;
            }
        }

        private void DragOrPickUp()
        {

            var inputPosition = CurrentTouchPosition;

            if (draggingItem)
            {

                draggedObject.transform.position = inputPosition + touchOffset;

            }
            else
            {

                RaycastHit2D[] touches = Physics2D.RaycastAll(inputPosition, inputPosition, 0.5f);
                if (touches.Length > 0)
                {
                    var hit = touches[0];
                    if (hit.transform != null && hit.rigidbody != null)
                    {
                        draggingItem = true;
                        draggedObject = hit.transform.gameObject;
                        touchOffset = (Vector2)hit.transform.position - inputPosition;
                    }
                }
            }
        }

        private bool HasInput
        {
            get
            {

                return Input.GetMouseButton(0);
            }
        }

        public void DropItem()
        {
            draggingItem = false;     

        }

    }

What does `OnTriggerStay2D` have to do with dragging object? — Programmer, Jul 02 '17 at 17:58
I'm dragging the object to collide to another one, but i don't want to destroy it when they collide, i want to destroy it when i release it if they are still touching. — Ed Arévalo, Jul 02 '17 at 18:25
That makes sense now. Please add your drag code too. That will help give you an answer. — Programmer, Jul 02 '17 at 18:42
You could just perform a RayCast, after you released the object. So you dont have to use the OnColliderStay Method. — fridayswag, Jul 02 '17 at 19:43

score 4 · Accepted Answer · answered Jul 02 '17 at 19:57

Avoid using OnTriggerStay2D for this. You can use a boolean variable that you set to true and false in the OnTriggerEnter2D and OnTriggerExit2D function.

bool isTouching = false;

void OnTriggerEnter2D(Collider2D collision)
{
    Debug.Log("Entered");
    if (collision.gameObject.CompareTag("YourOtherObject"))
    {
        isTouching = true;
    }
}

void OnTriggerExit2D(Collider2D collision)
{
    Debug.Log("Exited");
    if (collision.gameObject.CompareTag("YourOtherObject"))
    {
        isTouching = false;
    }
}

You can now check the isTouching variable when the object is released.

if(isTouching){
....
}

Note that I suggest you abandon your current code that uses Raycast and Input.GetMouseButton(0); since you are using this on mobile devices too. You should be using Unity's new EventSystem for this since it is made to be mobile friendly too.

Since you are using 2D collider, see #7 from this answer.

Here is a complete example of how to drag a Sprite with the new EventSystem. Combine that with the answer above and you get a much more better solution.

Thanks, Just by removing the OnTriggerStay2D and using the boolean as you said works perfectly, but i'm looking into your recommendation to improve it, but thank you very much, your solution really works. — Ed Arévalo, Jul 02 '17 at 20:26
Nice. Glad I was able to help and you definitely use that EventSystem I mentioned. — Programmer, Jul 02 '17 at 20:33

Unity3D using OnTriggerStay

1 Answers1