最新背包代码：
Unity3D — — UGUI之简易背包
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：
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using UnityEngine.EventSystems;
using UnityEngine.UI; public class InventoryItem : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler,IPointerEnterHandler
{
private Transform originalSlot;
private GameObject parent;
private GameObject item;
private float x_item;
private float y_item;
private Vector2 itemSize;
private bool isDragging = false; //默认设为false,否则OnPointerEnter每帧都会调用，会有bug /// <summary>
/// 添加CanvasGroup组件，在物品拖动时blocksRaycasts设置为false;
/// 让鼠标的Pointer射线穿过Item物体检测到UI下层的物体信息
/// </summary>
private CanvasGroup itemCanvasGroup; public string objectTag=null; private void Start()
{
itemCanvasGroup = this.GetComponent<CanvasGroup>();
item = this.transform.gameObject; x_item = item.GetComponent<Image>().GetPixelAdjustedRect().width; //Image的初始长宽
y_item = item.GetComponent<Image>().GetPixelAdjustedRect().height;
parent = GameObject.FindGameObjectWithTag("SlotGrid");
} public void OnPointerEnter(PointerEventData eventData)
{
//当鼠标在最外层时（移出背包，Canvas外）
//让物品回到原位
if(eventData.pointerCurrentRaycast.depth== && isDragging==true)
{
SetOriginalPos(this.gameObject);
return;
} //Debug.Log(eventData.pointerCurrentRaycast.depth);
objectTag = eventData.pointerCurrentRaycast.gameObject.tag;
Debug.Log("Raycast = "+objectTag); if(objectTag!=null && isDragging==true)
{ if (objectTag == Tags.InventorySlot) //如果是空格子，则放置Item
{
SetCurrentSlot(eventData);
}
else if (objectTag == Tags.InventoryItem) //交换物品
{
SwapItem(eventData);
}
else //如果都不是则返回原位
{
SetOriginalPos(this.gameObject);
}
}
} //把Item回归到原来位置
public void SetOriginalPos(GameObject gameobject)
{ gameobject.transform.SetParent(originalSlot);
gameobject.GetComponent<RectTransform>().anchoredPosition = originalSlot.GetComponent<RectTransform>().anchoredPosition;
itemCanvasGroup.blocksRaycasts = true;
} //交换两个物体
//由于拖放中，正被拖放的物体没有Block RayCast
//具体思路：
//1.记录当前射线照射到的物体（Item2）
//2.获取Item2的parent的位置信息，并把item1放过去
//3.把Item2放到Item1所在的位置
public void SwapItem(PointerEventData eventData)
{
GameObject targetItem = eventData.pointerCurrentRaycast.gameObject; //下面这两个方法不可颠倒，否则执行顺序不一样会出bug
//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）
//因此会把Item1也放到Item2下，变成都在原本Item1的Slot内
SetCurrentSlot(eventData);
SetOriginalPos(targetItem);
} //设置Item到当前鼠标所在的Slot
public void SetCurrentSlot(PointerEventData eventData)
{
//如果Slot为空
if (eventData.pointerCurrentRaycast.gameObject.tag==Tags.InventorySlot)
{
Transform currentSlot= eventData.pointerCurrentRaycast.gameObject.transform;
this.transform.SetParent(currentSlot);
//如果只是transform position，图片会默认在左上角顶点处的Anchor
//因此这里用anchoredPosition让Item图片填充满Slot
this.GetComponent<RectTransform>().anchoredPosition = currentSlot.GetComponent<RectTransform>().anchoredPosition;
}
else if(eventData.pointerCurrentRaycast.gameObject.tag == Tags.InventoryItem)
{
Transform currentSlot = eventData.pointerCurrentRaycast.gameObject.transform.parent;
this.transform.SetParent(currentSlot);
this.GetComponent<RectTransform>().anchoredPosition = currentSlot.GetComponent<RectTransform>().anchoredPosition;
}
} public void OnBeginDrag(PointerEventData eventData)
{
originalSlot = this.GetComponent<Transform>().parent; //每次拖拽开始前记录初始位置
isDragging = true;
itemCanvasGroup.blocksRaycasts = true;
item.transform.SetParent(parent.transform, false); // 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）
item.transform.SetAsLastSibling(); item.GetComponent<RectTransform>().SetSizeWithCurrentAnchors(RectTransform.Axis.Horizontal, x_item);
item.GetComponent<RectTransform>().SetSizeWithCurrentAnchors(RectTransform.Axis.Vertical, y_item);
} public void OnDrag(PointerEventData eventData)
{
itemCanvasGroup.blocksRaycasts = false;
DragPos(eventData);
//OnPointerEnter(eventData);
} public void OnEndDrag(PointerEventData eventData)
{
OnPointerEnter(eventData);
itemCanvasGroup.blocksRaycasts = true;
isDragging = false;
} //获取鼠标当前位置，并赋给item
private void DragPos(PointerEventData eventData)
{
RectTransform RectItem = item.GetComponent<RectTransform>();
Vector3 globalMousePos;
if (RectTransformUtility.ScreenPointToWorldPointInRectangle(item.transform as RectTransform, eventData.position, eventData.pressEventCamera, out globalMousePos))
{
RectItem.position = globalMousePos;
}
}
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
public bool dragOnSurfaces = true;
private GameObject m_DraggingIcon;
private RectTransform m_DraggingPlane;
public void OnBeginDrag(PointerEventData eventData)
{
//找到有Canvas组件的物体
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.
//给实例化的新GameObject命名
m_DraggingIcon = new GameObject(this.name);
//放到指定路径
m_DraggingIcon.transform.SetParent(canvas.transform, false);
//Move the transform to the end of the local transform list.
//Puts the panel to the front as it is now the last UI element to be drawn.
m_DraggingIcon.transform.SetAsLastSibling();
//给新GameObject添加<Image>组件
var image = m_DraggingIcon.AddComponent<Image>();
//把当前脚本所挂载的物体的图片赋给新GameObject
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);
}
//实现不断往相应的上层parent查找所需组件
//Component: Base class for everything attached to GameObjects.
static public T FindInParents<T>(GameObject go) where T : Component
{
//如果go为null，返回null
if (go == null) return null;
//查找go身上相应组件（Canvas）
//找到后返回comp
var comp = go.GetComponent<T>();
if (comp != null)
return comp;
//查找t的parent
//循环查找，不断往上层找parent，直到找到相应组件（Canvas）
Transform t = go.transform.parent;
while (t != null && comp == null) //t有上层parent && 第1步里未找到组件
{
comp = t.gameObject.GetComponent<T>();
t = t.parent;
}
return comp;
}
UnityAPI手册内的代码
三、实现
如图是整个背包的UI层级，每个Slot和里面的Item都是Prefab，把脚本挂在InventoryItem上即可实现