Interface IDragHandler
Interface to implement if you wish to receive OnDrag callbacks.
Namespace: UnityEngine.EventSystems
Assembly: UnityEngine.UI.dll
Syntax
public interface IDragHandler : IEventSystemHandler
Remarks
Criteria for this event is implementation dependent. For example see StandAloneInputModule.
Examples
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
[RequireComponent(typeof(Image))]
public class DragMe : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
public bool dragOnSurfaces = true;
private GameObject m_DraggingIcon;
private RectTransform m_DraggingPlane;
public 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();
var image = m_DraggingIcon.AddComponent<Image>();
image.sprite = GetComponent<Image>().sprite;
image.SetNativeSize();
if (dragOnSurfaces)
m_DraggingPlane = transform as RectTransform;
else
m_DraggingPlane = canvas.transform as RectTransform;
SetDraggedPosition(eventData);
}
public void OnDrag(PointerEventData data)
{
if (m_DraggingIcon != null)
SetDraggedPosition(data);
}
private void SetDraggedPosition(PointerEventData data)
{
if (dragOnSurfaces && data.pointerEnter != null && data.pointerEnter.transform as RectTransform != null)
m_DraggingPlane = data.pointerEnter.transform as RectTransform;
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 void OnEndDrag(PointerEventData eventData)
{
if (m_DraggingIcon != null)
Destroy(m_DraggingIcon);
}
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;
}
}
Methods
OnDrag(PointerEventData)
When dragging is occurring this will be called every time the cursor is moved.
Declaration
void OnDrag(PointerEventData eventData)
Parameters
Type | Name | Description |
---|---|---|
PointerEventData | eventData |