Drag and Drop Problem

Hi i have some problems with the drag and drop functionality for UI elements. In the picture below i show you the overview of the inventory and marked all the elements i used and what you can see in the hierarchy!

If i take one Item (EquipImage) and drag it from the “EquipmentItemsParent” away and i release the mouse, the item snaps correctly back to its origin position in the correct slot. But if i take one item and want to drop it in one of the slots (Head, Jacket, Shoes, etc) in the “Characterpanel” the item or the image of the item is not in the center of the slot, but -50 to the left on the x axis. Shown in the picture below.

The next bug is if i want to drag and drop the item back to the inventory slots on the left (“EquipmentItemsParent”) the drag an drop is working and it snaps back to the center of the slot but while i drag the item from the right to the left, the item disappear behinf the “StaticItemsParent” and the “EquipmentItemsParent” Panel. How can i solve these things? The code of this i show you in the following post. Thank you!

Draggable Script:

using System.Collections;
using UnityEngine;
using UnityEngine.EventSystems;

public class Draggable : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{

	public Transform parentToReturnTo = null;

	public void OnBeginDrag (PointerEventData eventData)
	{
		parentToReturnTo = this.transform.parent;
		this.transform.SetParent (this.transform.parent);

		GetComponent<CanvasGroup> ().blocksRaycasts = false;
	}

	public void OnDrag (PointerEventData eventData)
	{
		//this.transform.position = eventData.position;
		transform.position = eventData.position;
	}

	public void OnEndDrag (PointerEventData eventData)
	{
		this.transform.SetParent (parentToReturnTo);
		GetComponent<CanvasGroup> ().blocksRaycasts = true;
		this.transform.localPosition = Vector3.zero;
	}

}

ItemDropZone Script:

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

public class ItemDropZone : MonoBehaviour, IDropHandler {

	public void OnDrop (PointerEventData eventData)
	{
		Draggable d = eventData.pointerDrag.GetComponent<Draggable> ();
		if(d != null )
		{
			d.parentToReturnTo = this.transform;
		}

	}
}

The Items (EquipImage) have the Draggable Script attached and the Slots the Dropzone Script! Thx for help!

@Legend_Bacon maybe you have a clue/hint? :slight_smile: Thx

Hello there,

I am at work and can’t give you a proper answer right now, but this should be a start:


Bug #1: Several possibilities here.

  • Sometimes the UI doesn’t refresh immediately. Try hitting Ctrl + R when it does that bug, or resize the game window. Does it fix itself?
  • If not, try setting the ANCHOR POSITION to zero instead of doing this.transform.localPosition = Vector3.zero;.

Bug #2: This one is due to the object being a child of “HeadSlot”. The Canvas in Unity draws object from top to bottom, so what happens is:

  1. “HeadSlot” and its children get drawn
  2. “StaticItemsParent” gets drawn on top of it
  3. Etc.

Basically, because of the new parenting your object now has in the hierarchy, it gets drawn before some other UI elements, and therefore is hidden by those drawn on top. To fix this, parent your object to your Canvas (either reference the Canvas directly or use transform.root) on OnBeginDrag(). and then parent it to the proper parent on OnEndDrag().

Judging by your variable names, you might have already seen it. But if not, THIS is a very good resource for drag & drop features.


Hope that helps!

Cheers,

~LegendBacon