Prevent IDragHandler from also triggering PointerClickHandler?

Question

Hello! I'm working on an inventory script and having a bit of trouble with the IPointerClickHandler and the IDragHandler. Currently, my code executes everything in OnDrag() and OnEndDrag() properly, but when i let go of an item, it also registers a normal LMB click. How to prevent this?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.EventSystems;
 
 public class ItemClickHandler : MonoBehaviour, IDragHandler, IEndDragHandler, IPointerClickHandler
 {
     public Transform itemMenu;
     public Transform inventory;
     public Transform slot;
 
     //Store currently dragged item
 
     public void OnDrag(PointerEventData dragData)
     {
         transform.position = Input.mousePosition;
         transform.SetParent(inventory);
         transform.SetAsLastSibling();
     }
 
     public void OnEndDrag(PointerEventData endDragData)
     {
         transform.SetParent(slot);
         transform.SetAsLastSibling();
         transform.localPosition = Vector3.zero;
         
         //assign currently dragged item to the inventory slot array it was dropped on and put old otem in the old slot
     }
 
     public void OnPointerClick(PointerEventData eventData)
     {
         if (eventData.button == PointerEventData.InputButton.Left)
         {
             Debug.Log("Using item in " + name);
             //USE ITEM
         }
         else if (eventData.button == PointerEventData.InputButton.Middle)
         {
             //if item associated with inventory slot isStackable, split stack.
             //change split size with mouse wheel
         }
         else if (eventData.button == PointerEventData.InputButton.Right)
         {
             Debug.Log("Opening item menu for " + name);
             //OPEN ITEM MENU
         }
     }
 }

Answer 1

Best Answer

Answer by Jonathan-Bro · Sep 27, 2018 at 06:35 AM

That does seem silly that OnPointerClick is executed after releasing the mouse button after a drag.

You can detect if you dragged the mouse or not by evaluating the distance between when you pressed the mouse button and when you released it.

 float dragDistance = Vector2.Distance( eventData.pressPosition, eventData.position );
 float dragThreshold = 10f;
 bool isDrag = dragDistance > dragThreshold ;
 
 if( isDrag )
      return;

Update!

KillHour 's newer answer below is more elegantly handled. I recommend that approach instead of this.

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$$anonymous$$ · Sep 30, 2018 at 06:54 AM 0

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Thank you, i figured I'd have to go with something like this but for some reason distance wasnt co$$anonymous$$g to $$anonymous$$d and I was attempting to build it off click time, which was a bit awkward.

Unfortunately, the drag handler is a bit too clunky for my UI elements and slow initial response to the drag is causing some bugs, so I think I'll just need to build my own. Thanks though

Answer 2

Answer by KillHour · Jan 14 at 02:14 AM

Since I ran into this problem myself and this is the first thing that pops up on Google, I thought I'd share my solution. If the click happens at the end of the drag, PointerEventData.dragging returns true, so you can just check for that and return. Here's my code:

 public void OnPointerClick(PointerEventData eventData) {
     if (eventData.dragging) {
         return;
     }
     switch(eventData.button) {
         case PointerEventData.InputButton.Left:
             Rotate(1);
             return;
         case PointerEventData.InputButton.Right:
             Rotate(3);
             return;
         default:
             return;
     }
 }

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Prevent IDragHandler from also triggering PointerClickHandler?

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