Unity版本：2017.3
功能：用UGUI实现简单的背包物品拖放/交换功能
一、简介
在UGUI下，物品的拖放脚本实现主要依赖于UnityEngine.EventSystems下的三个接口 IBeginDragHandler, IDragHandler, IEndDragHandler； 其次还有IPointerEnterHandler，IPointerExitHandler
等接口来实现鼠标移入移出等操作的监控，同时引用这些接口后，对应的方法也是必须要实现的
简单介绍下这几个方法：
官方API解释：PointerEventData - - Event payload associated with pointer (mouse / touch) events.
Drag类：
OnBeginDrag(PointerEventData eventData) ：当点击物体后开始执行此方法
OnDrag(PointerEventData eventData) ：在拖拽中过程中执行
OnEndDrag(PointerEventData eventData) ：拖拽结束时执行（松开鼠标的那下）
Pointer类：
OnPointerEnter(PointerEventData eventData) ：当鼠标进入时执行
其余的类似OnPointerExit方法基本类似
Drop类：（待研究）
IDropHandler下的OnDrop(PointerEventData eventData)
这个方法笔者没有过多研究，由于拖放物品结束后的功能（交换/摧毁等）由EndDrag方法实现了，未发现OnDrop的具体用法
二、功能实现
注：由于未导入具体的物品信息，因此目前只是实现简单的GameObject间的拖放关系
（1）背包内物体的拖放，并在结束后指定到相应的格子下
（2）当物品未在格子内或者超出背包范围时，归位到原本的位置
（3）两个物体间互相交换
大致样子如下：
代码：
1 using System.Collections;
2 using System.Collections.Generic;
3 using UnityEngine;
4 using UnityEditor;
5 using UnityEngine.EventSystems;
6 using UnityEngine.UI;
7
8 public class InventoryItem : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler,IPointerEnterHandler
9 {
10 private Transform originalSlot;
11 private GameObject parent;
12 private GameObject item;
13 private float x_item;
14 private float y_item;
15 private Vector2 itemSize;
16 private bool isDragging = false; //默认设为false,否则OnPointerEnter每帧都会调用，会有bug
17
18 /// <summary>
19 /// 添加CanvasGroup组件，在物品拖动时blocksRaycasts设置为false;
20 /// 让鼠标的Pointer射线穿过Item物体检测到UI下层的物体信息
21 /// </summary>
22 private CanvasGroup itemCanvasGroup;
23
24 public string objectTag=null;
25
26 private void Start()
27 {
28 itemCanvasGroup = this.GetComponent<CanvasGroup>();
29 item = this.transform.gameObject;
30
31 x_item = item.GetComponent<Image>().GetPixelAdjustedRect().width; //Image的初始长宽
32 y_item = item.GetComponent<Image>().GetPixelAdjustedRect().height;
33 parent = GameObject.FindGameObjectWithTag("SlotGrid");
34 }
35
36 public void OnPointerEnter(PointerEventData eventData)
37 {
38 //当鼠标在最外层时（移出背包，Canvas外）
39 //让物品回到原位
40 if(eventData.pointerCurrentRaycast.depth==0 && isDragging==true)
41 {
42 SetOriginalPos(this.gameObject);
43 return;
44 }
45
46 //Debug.Log(eventData.pointerCurrentRaycast.depth);
47 objectTag = eventData.pointerCurrentRaycast.gameObject.tag;
48 Debug.Log("Raycast = "+objectTag);
49
50
51 if(objectTag!=null && isDragging==true)
52 {
53
54 if (objectTag == Tags.InventorySlot) //如果是空格子，则放置Item
55 {
56 SetCurrentSlot(eventData);
57 }
58 else if (objectTag == Tags.InventoryItem) //交换物品
59 {
60 SwapItem(eventData);
61 }
62 else //如果都不是则返回原位
63 {
64 SetOriginalPos(this.gameObject);
65 }
66 }
67 }
68
69 //把Item回归到原来位置
70 public void SetOriginalPos(GameObject gameobject)
71 {
72
73 gameobject.transform.SetParent(originalSlot);
74 gameobject.GetComponent<RectTransform>().anchoredPosition = originalSlot.GetComponent<RectTransform>().anchoredPosition;
75 itemCanvasGroup.blocksRaycasts = true;
76 }
77
78 //交换两个物体
79 //由于拖放中，正被拖放的物体没有Block RayCast
80 //具体思路：
81 //1.记录当前射线照射到的物体（Item2）
82 //2.获取Item2的parent的位置信息，并把item1放过去
83 //3.把Item2放到Item1所在的位置
84 public void SwapItem(PointerEventData eventData)
85 {
86 GameObject targetItem = eventData.pointerCurrentRaycast.gameObject;
87
88 //下面这两个方法不可颠倒，否则执行顺序不一样会出bug
89 //BUG：先把Item2放到了Item1的位置，此时Item1得到的位置信息是传递后的Item2的（原本Item1的位置）
90 //因此会把Item1也放到Item2下，变成都在原本Item1的Slot内
91 SetCurrentSlot(eventData);
92 SetOriginalPos(targetItem);
93 }
94
95 //设置Item到当前鼠标所在的Slot
96 public void SetCurrentSlot(PointerEventData eventData)
97 {
98 //如果Slot为空
99 if (eventData.pointerCurrentRaycast.gameObject.tag==Tags.InventorySlot)
100 {
101 Transform currentSlot= eventData.pointerCurrentRaycast.gameObject.transform;
102 this.transform.SetParent(currentSlot);
103 //如果只是transform position，图片会默认在左上角顶点处的Anchor
104 //因此这里用anchoredPosition让Item图片填充满Slot
105 this.GetComponent<RectTransform>().anchoredPosition = currentSlot.GetComponent<RectTransform>().anchoredPosition;
106 }
107 else if(eventData.pointerCurrentRaycast.gameObject.tag == Tags.InventoryItem)
108 {
109 Transform currentSlot = eventData.pointerCurrentRaycast.gameObject.transform.parent;
110 this.transform.SetParent(currentSlot);
111 this.GetComponent<RectTransform>().anchoredPosition = currentSlot.GetComponent<RectTransform>().anchoredPosition;
112 }
113 }
114
115 public void OnBeginDrag(PointerEventData eventData)
116 {
117 originalSlot = this.GetComponent<Transform>().parent; //每次拖拽开始前记录初始位置
118 isDragging = true;
119 itemCanvasGroup.blocksRaycasts = true;
120 item.transform.SetParent(parent.transform, false);
121
122 // 将item设置到当前UI层级的最下面（最表面，防止被同一层级的UI覆盖）
123 item.transform.SetAsLastSibling();
124
125 item.GetComponent<RectTransform>().SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, x_item);
126 item.GetComponent<RectTransform>().SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, y_item);
127 }
128
129 public void OnDrag(PointerEventData eventData)
130 {
131 itemCanvasGroup.blocksRaycasts = false;
132 DragPos(eventData);
133 //OnPointerEnter(eventData);
134 }
135
136 public void OnEndDrag(PointerEventData eventData)
137 {
138 OnPointerEnter(eventData);
139 itemCanvasGroup.blocksRaycasts = true;
140 isDragging = false;
141 }
142
143 //获取鼠标当前位置，并赋给item
144 private void DragPos(PointerEventData eventData)
145 {
146 RectTransform RectItem = item.GetComponent<RectTransform>();
147 Vector3 globalMousePos;
148 if (RectTransformUtility.ScreenPointToWorldPointInRectangle(item.transform as RectTransform, eventData.position, eventData.pressEventCamera, out globalMousePos))
149 {
150 RectItem.position = globalMousePos;
151 }
152 }
InventoryItem
Unity官方的的实现代码：
官方的的代码实现的是拖动物体时生成一个新的Gamobject
下面是官方代码加自己的一些注释
1 public bool dragOnSurfaces = true;
2
3 private GameObject m_DraggingIcon;
4 private RectTransform m_DraggingPlane;
5
6 public void OnBeginDrag(PointerEventData eventData)
7 {
8 //找到有Canvas组件的物体
9 var canvas = FindInParents<Canvas>(gameObject);
10
11 if (canvas == null)
12 return;
13
14 //We have clicked something that can be dragged.
15 // What we want to do is create an icon for this.
16 //给实例化的新GameObject命名
17 m_DraggingIcon = new GameObject(this.name);
18 //放到指定路径
19 m_DraggingIcon.transform.SetParent(canvas.transform, false);
20
21 //Move the transform to the end of the local transform list.
22 //Puts the panel to the front as it is now the last UI element to be drawn.
23 m_DraggingIcon.transform.SetAsLastSibling();
24
25 //给新GameObject添加<Image>组件
26 var image = m_DraggingIcon.AddComponent<Image>();
27 //把当前脚本所挂载的物体的图片赋给新GameObject
28 image.sprite = GetComponent<Image>().sprite;
29 image.SetNativeSize();
30
31
32 if (dragOnSurfaces)
33 m_DraggingPlane = transform as RectTransform;
34 else
35 m_DraggingPlane = canvas.transform as RectTransform;
36
37
38 SetDraggedPosition(eventData);
39 }
40
41 public void OnDrag(PointerEventData data)
42 {
43 if (m_DraggingIcon != null)
44 SetDraggedPosition(data);
45 }
46
47 private void SetDraggedPosition(PointerEventData data)
48 {
49
50 if (dragOnSurfaces && data.pointerEnter != null && data.pointerEnter.transform as RectTransform != null)
51 m_DraggingPlane = data.pointerEnter.transform as RectTransform;
52
53 var rt = m_DraggingIcon.GetComponent<RectTransform>();
54 Vector3 globalMousePos;
55 if (RectTransformUtility.ScreenPointToWorldPointInRectangle(m_DraggingPlane, data.position, data.pressEventCamera, out globalMousePos))
56 {
57 rt.position = globalMousePos;
58 rt.rotation = m_DraggingPlane.rotation;
59 }
60 }
61
62 public void OnEndDrag(PointerEventData eventData)
63 {
64 if (m_DraggingIcon != null)
65 Destroy(m_DraggingIcon);
66 }
67
68 //实现不断往相应的上层parent查找所需组件
69 //Component: Base class for everything attached to GameObjects.
70 static public T FindInParents<T>(GameObject go) where T : Component
71 {
72 //如果go为null，返回null
73 if (go == null) return null;
74
75
76 //查找go身上相应组件（Canvas）
77 //找到后返回comp
78 var comp = go.GetComponent<T>();
79 if (comp != null)
80 return comp;
81
82 //查找t的parent
83 //循环查找，不断往上层找parent，直到找到相应组件（Canvas）
84 Transform t = go.transform.parent;
85 while (t != null && comp == null) //t有上层parent && 第1步里未找到组件
86 {
87 comp = t.gameObject.GetComponent<T>();
88 t = t.parent;
89 }
90 return comp;
91 }
UnityAPI手册内的代码
三、实现思路
原文地址：https://www.cnblogs.com/QQW123/p/9663609.html
时间： 2024-10-11 00:16:27