unity 实现UI-背包装备拖拽功能

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
public class Drag : MonoBehaviour, IBeginDragHandler, IEndDragHandler, IDragHandler, ICanvasRaycastFilter
{
    private Transform nowparent;//记录原始坐标位置
    private bool isRaycastLocationValid = true;//默认射线不能穿透物体
    public Transform IconList;
    /// 
    /// 开始拖拽
    /// 
    public void OnBeginDrag(PointerEventData eventData)
    {
        this.transform.SetAsLastSibling();
//1.SetAsFirstSibling();

//2.SetAsLastSibling();

//3.SetSiblingIndex(n)

//SetAsFirstSibling()是设置为最先渲染的，即会被后渲染的挡住。

//SetAsLastSibling();是设置为最后渲染的，即会挡住比他先渲染的

//SetSiblingIndex(n)是设置层级，从0开始到childcount -1

//当n为0时，其效果与SetAsFirstSibling();相同

//但是当层级小于0时，其效果与SetAsLastSibling()一致

//当层级为大于等于transform.parent.childCount - 1时，其效果与SetAsLastSibling一致
        nowparent =this.transform.parent;//初始位置
        isRaycastLocationValid = false;//设置为可以穿透
        transform.SetParent(IconList);//将当前拖拽的物品放在最外层下 效果：可以挡住随意UI 避免呗其他UI挡住
    }
    /// 
    /// UI跟随 鼠标
    /// 
    /// 
    public void OnDrag(PointerEventData eventData)
    {
        transform.position = Input.mousePosition;
    }
    /// 
    /// 拖拽结束
    /// 
    public void OnEndDrag(PointerEventData eventData)
    {
         //获取鼠标终点位置可能存在的物品
         GameObject go = eventData.pointerCurrentRaycast.gameObject;
        if (go != null)//落点位置不为空
        {
            Debug.Log(go.name);//打印一下落点位置名称
            if (go.tag == ("Gird"))//鼠标终点位置是空格子
            {
                Debug.Log("空格子");
                SetParentAndPosition(transform, go.transform);
            }
            else if (go.tag == transform.tag)//标签相同 放回
            {
                //将拖拽的物品1放到鼠标终点下的位置
                SetParentAndPosition(transform, go.transform);
            }
            else//无效位置，物品回到原来的位置
            {
                SetParentAndPosition(transform, nowparent);
            }
        }
        else
        {
            SetParentAndPosition(transform, nowparent);
        }
        isRaycastLocationValid = true;//射线不可以穿透物体
    }
    // 将child放到parent下做其子物体
    private void SetParentAndPosition(Transform child, Transform parent)
    {
        child.SetParent(parent);
        child.position = parent.position;//子物体的坐标跟随父物体
    }
    public bool IsRaycastLocationValid(Vector2 sp, Camera eventCamera)
    {
        return isRaycastLocationValid;
    }
}

2.鼠标拖动UI并限制拖动区域（参考地址：Unity UI拖拽及拖拽范围限制功能的实现_疯狂的窝瓜的博客-CSDN博客）

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

public class DragItme : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
    [Header("表示限制的区域")]
    public RectTransform LimitContainer;
    [Header("场景中Canvas")]
    public Canvas canvas;

    RectTransform rt;
    // 位置偏移量
    Vector3 offset = Vector3.zero;
    // 最小、最大X、Y坐标
    float minX, maxX, minY, maxY;

    public GameObject itme;
    public Transform tr;

    public Toggle ThisToggle;
    void Start()
    {
        rt = GetComponent();
    }
    void Update()
    {
        if ( ThisToggle.isOn)
        {
          //  Debug.Log("name=" + this.gameObject.name);
          
        }
        if (Input.GetKey(KeyCode.Delete)&& ThisToggle.isOn)
        {
            Debug.Log("name=" + this.gameObject.name);
            Destroy(this.gameObject);
        }
    }
    /// 
    /// 开始拖拽
    /// 
    /// 
    public void OnBeginDrag(PointerEventData eventData)
    {
        if (eventData.button != PointerEventData.InputButton.Left)
            return;
        //var go= GameObject.Instantiate(itme, tr);
        //go.name = "DragItme";

        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, eventData.position, eventData.enterEventCamera, out Vector3 globalMousePos))
        {
            // 计算偏移量
            offset = rt.position - globalMousePos;
            // 设置拖拽范围
            SetDragRange();
        }
    }
    /// 
    /// 创建UI
    /// 
    /// 
    /// 
    public static GameObject CreationUI(string name, Transform uILayer)
    {
        Debug.Log("创建UI " + name);
        var tempObject = Resources.Load("prefab/UI/" + name) as GameObject;
        GameObject.Instantiate(tempObject, uILayer);
        return tempObject;
    }
    /// 
    /// 拖拽中
    /// 
    /// 
    public void OnDrag(PointerEventData eventData)
    {
        if (eventData.button != PointerEventData.InputButton.Left)
            return;
        // 将屏幕空间上的点转换为位于给定RectTransform平面上的世界空间中的位置
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, eventData.position, eventData.pressEventCamera, out Vector3 globalMousePos))
        {
            rt.position = DragRangeLimit(globalMousePos + offset);
        }
       
    }
    /// 
    /// 拖拽结束
    /// 
    public void OnEndDrag(PointerEventData eventData)
    {
        this.transform.GetComponent().isOn = false;
        Debug.Log("name=" + this.name);
    }
    /// 
    /// 设置最大、最小坐标
    /// 
    void SetDragRange()
    {
        // 最小x坐标 = 容器当前x坐标 - 容器轴心距离左边界的距离 + UI轴心距离左边界的距离
        minX = LimitContainer.position.x
            - LimitContainer.pivot.x * LimitContainer.rect.width * canvas.scaleFactor
            + rt.rect.width * canvas.scaleFactor * rt.pivot.x;
        // 最大x坐标 = 容器当前x坐标 + 容器轴心距离右边界的距离 - UI轴心距离右边界的距离
        maxX = LimitContainer.position.x
            + (1 - LimitContainer.pivot.x) * LimitContainer.rect.width * canvas.scaleFactor
            - rt.rect.width * canvas.scaleFactor * (1 - rt.pivot.x);

        // 最小y坐标 = 容器当前y坐标 - 容器轴心距离底边的距离 + UI轴心距离底边的距离
        minY = LimitContainer.position.y
            - LimitContainer.pivot.y * LimitContainer.rect.height * canvas.scaleFactor
            + rt.rect.height * canvas.scaleFactor * rt.pivot.y;

        // 最大y坐标 = 容器当前x坐标 + 容器轴心距离顶边的距离 - UI轴心距离顶边的距离
        maxY = LimitContainer.position.y
            + (1 - LimitContainer.pivot.y) * LimitContainer.rect.height * canvas.scaleFactor
            - rt.rect.height * canvas.scaleFactor * (1 - rt.pivot.y);
    }
    /// 
    /// 限制坐标范围
    /// 
    /// 
    /// 
    Vector3 DragRangeLimit(Vector3 pos)
    {
        pos.x = Mathf.Clamp(pos.x, minX, maxX);
        pos.y = Mathf.Clamp(pos.y, minY, maxY);
        return pos;
    }
}