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using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
[RequireComponent(typeof(Image))]
public class Dragable : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
protected GameObject m_DraggingIcon;
protected RectTransform m_DraggingPlane;
public virtual void OnBeginDrag(PointerEventData eventData)
{
var canvas = FindInParents<Canvas>(gameObject);
if (canvas == null)
return;
// We have clicked something that can be dragged.
// What we want to do is create an icon for this.
m_DraggingIcon = new GameObject("icon");
m_DraggingIcon.transform.SetParent(canvas.transform, false);
m_DraggingIcon.transform.SetAsLastSibling();
m_DraggingIcon.layer = LayerMask.NameToLayer("Ignore Raycast");
var image = m_DraggingIcon.AddComponent<Image>();
image.sprite = GetComponent<Image>().sprite;
image.SetNativeSize();
m_DraggingPlane = canvas.transform as RectTransform;
SetDraggedPosition(eventData);
}
public virtual void OnDrag(PointerEventData data)
{
if (m_DraggingIcon != null)
SetDraggedPosition(data);
}
protected virtual void SetDraggedPosition(PointerEventData data)
{
var rt = m_DraggingIcon.GetComponent<RectTransform>();
Vector3 globalMousePos;
if (RectTransformUtility.ScreenPointToWorldPointInRectangle(m_DraggingPlane, data.position, data.pressEventCamera, out globalMousePos))
{
rt.position = globalMousePos;
rt.rotation = m_DraggingPlane.rotation;
}
}
public virtual void OnEndDrag(PointerEventData eventData)
{
Destroy(m_DraggingIcon);
m_DraggingIcon = null;
}
static public T FindInParents<T>(GameObject go) where T : Component
{
if (go == null) return null;
var comp = go.GetComponent<T>();
if (comp != null)
return comp;
Transform t = go.transform.parent;
while (t != null && comp == null)
{
comp = t.gameObject.GetComponent<T>();
t = t.parent;
}
return comp;
}
}