UGUI控制元件的事件響應有很多種方式，比如使用元件EventTrigger來新增事件監聽，或者實現IDragHandler等介面，或者更直接地繼承EventTrigger來進行更靈話的呼叫。

下面分別就上面3種監聽方式進行講解，這些例子都是實現拖動Image的功能。

一、使用元件EventTrigger來新增事件監聽

新增一個指令碼EventTriggerTest，掛到一個Image上。那麼OK，現在可以拖動圖片了。

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1. using UnityEngine;  
2. using UnityEngine.EventSystems;  
3. using Framework;  
4.   
5. public class EventTriggerTest : MonoBehaviour  
6. {  
7.     public void OnDrag(BaseEventData baseEventData)  
8.     {  
9.         PointerEventData data = baseEventData as PointerEventData;  
10.         var rt = data.pointerPress.GetComponent<RectTransform>();  
11.         Vector3 globalMousePos;  
12.         if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, data.position, data.pressEventCamera, out globalMousePos))  
13.         {  
14.             rt.position = globalMousePos;  
15.         }  
16.     }  
17. }  

using UnityEngine;
using UnityEngine.EventSystems;
using Framework;

public class EventTriggerTest : MonoBehaviour
{
    public void OnDrag(BaseEventData baseEventData)
    {
        PointerEventData data = baseEventData as PointerEventData;
        var rt = data.pointerPress.GetComponent<RectTransform>();
        Vector3 globalMousePos;
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, data.position, data.pressEventCamera, out globalMousePos))
        {
            rt.position = globalMousePos;
        }
    }
}

二、實現IDragHandler等介面

UGUI的所有介面如下

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1. IPointerEnterHandler,  
2. IPointerExitHandler,  
3. IPointerDownHandler,  
4. IPointerUpHandler,  
5. IPointerClickHandler,  
6. IInitializePotentialDragHandler,  
7. IBeginDragHandler,  
8. IDragHandler,  
9. IEndDragHandler,  
10. IDropHandler,  
11. IScrollHandler,  
12. IUpdateSelectedHandler,  
13. ISelectHandler,  
14. IDeselectHandler,  
15. IMoveHandler,  
16. ISubmitHandler,  
17. ICancelHandler  

        IPointerEnterHandler,
        IPointerExitHandler,
        IPointerDownHandler,
        IPointerUpHandler,
        IPointerClickHandler,
        IInitializePotentialDragHandler,
        IBeginDragHandler,
        IDragHandler,
        IEndDragHandler,
        IDropHandler,
        IScrollHandler,
        IUpdateSelectedHandler,
        ISelectHandler,
        IDeselectHandler,
        IMoveHandler,
        ISubmitHandler,
        ICancelHandler

這裡就實現IDragHandler介面，來實現Image的拖動。新增指令碼EventInterfaceTest，掛到Image上。

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1. using UnityEngine;  
2. using UnityEngine.EventSystems;  
3.   
4. class EventInterfaceTest : MonoBehaviour, IDragHandler  
5. {  
6.     public void OnDrag(PointerEventData data)  
7.     {  
8.         var rt = gameObject.GetComponent<RectTransform>();  
9.         Vector3 globalMousePos;  
10.         if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, data.position, data.pressEventCamera, out globalMousePos))  
11.         {  
12.             rt.position = globalMousePos;  
13.         }  
14.     }  
15. }  

using UnityEngine;
using UnityEngine.EventSystems;

class EventInterfaceTest : MonoBehaviour, IDragHandler
{
    public void OnDrag(PointerEventData data)
    {
        var rt = gameObject.GetComponent<RectTransform>();
        Vector3 globalMousePos;
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, data.position, data.pressEventCamera, out globalMousePos))
        {
            rt.position = globalMousePos;
        }
    }
}

三、繼承EventTrigger來進行更靈話的呼叫

如果GameObject是動態建立的，那麼就不方便用Unity編輯器加EventTrigger監聽，所以要是能用程式碼方便地進行監聽，又不需要重寫那麼多介面，那是最好不過了。

首先新增指令碼UGUIEventTrigger

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1. using System.Collections.Generic;  
2. using UnityEngine;  
3. using UnityEngine.EventSystems;  
4. using UnityEngine.Events;  
5.   
6. namespace Framework  
7. {  
8.     public class UGUIEventTrigger : EventTrigger  
9.     {  
10.         public static UGUIEventTrigger Get(GameObject go)  
11.         {  
12.             UGUIEventTrigger trigger = go.GetComponent<UGUIEventTrigger>();  
13.             if (null == trigger)  
14.             {  
15.                 trigger = go.AddComponent<UGUIEventTrigger>();  
16.             }  
17.             return trigger;  
18.         }  
19.   
20.         public void AddEventListener(EventTriggerType eventTriggerType, UnityAction<BaseEventData> action)  
21.         {  
22.             EventTrigger.Entry entry = new EventTrigger.Entry();  
23.             entry.eventID = eventTriggerType;  
24.             entry.callback.AddListener(action);  
25.             if (null == delegates)  
26.             {  
27.                 delegates = new List<Entry>();  
28.             }  
29.             delegates.Add(entry);  
30.         }  
31.     }  
32. }  

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

namespace Framework
{
    public class UGUIEventTrigger : EventTrigger
    {
        public static UGUIEventTrigger Get(GameObject go)
        {
            UGUIEventTrigger trigger = go.GetComponent<UGUIEventTrigger>();
            if (null == trigger)
            {
                trigger = go.AddComponent<UGUIEventTrigger>();
            }
            return trigger;
        }

        public void AddEventListener(EventTriggerType eventTriggerType, UnityAction<BaseEventData> action)
        {
            EventTrigger.Entry entry = new EventTrigger.Entry();
            entry.eventID = eventTriggerType;
            entry.callback.AddListener(action);
            if (null == delegates)
            {
                delegates = new List<Entry>();
            }
            delegates.Add(entry);
        }
    }
}

然後編寫測試指令碼，掛到Image上。

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1. using UnityEngine;  
2. using UnityEngine.EventSystems;  
3.   
4. public class UGUIEventTriggerTest : MonoBehaviour  
5. {  
6.     void Start()  
7.     {  
8.         UGUIEventTrigger.Get(gameObject).AddEventListener(EventTriggerType.Drag, OnDrag);  
9.     }  
10.   
11.     private void OnDrag(BaseEventData baseData)  
12.     {  
13.         PointerEventData data = baseData as PointerEventData;  
14.         var rt = data.pointerPress.GetComponent<RectTransform>();  
15.         Vector3 globalMousePos;  
16.         if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, data.position, data.pressEventCamera, out globalMousePos))  
17.         {  
18.             rt.position = globalMousePos;  
19.         }  
20.     }  
21. }  

using UnityEngine;
using UnityEngine.EventSystems;

public class UGUIEventTriggerTest : MonoBehaviour
{
    void Start()
    {
        UGUIEventTrigger.Get(gameObject).AddEventListener(EventTriggerType.Drag, OnDrag);
    }

    private void OnDrag(BaseEventData baseData)
    {
        PointerEventData data = baseData as PointerEventData;
        var rt = data.pointerPress.GetComponent<RectTransform>();
        Vector3 globalMousePos;
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, data.position, data.pressEventCamera, out globalMousePos))
        {
            rt.position = globalMousePos;
        }
    }
}

原地址：https://blog.csdn.net/gcs6564157/article/details/54767452