Unity realizes UI backpack equipment dragging function

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
public class Drag : MonoBehaviour, IBeginDragHandler, IEndDragHandler, IDragHandler, ICanvasRaycastFilter
{
    private Transform nowparent;// Record the original coordinate position 
    private bool isRaycastLocationValid = true;// By default, rays cannot penetrate objects 
    public Transform IconList;
    /// <summary>
    ///  Start dragging 
    /// </summary>
    public void OnBeginDrag(PointerEventData eventData)
    {
        this.transform.SetAsLastSibling();
        nowparent =this.transform.parent;// initial position 
        isRaycastLocationValid = false;// Set to be able to penetrate 
        transform.SetParent(IconList);// Put the currently dragged item under the outermost layer   effect ： Can block random UI  Avoid others UI Block 
    }
    /// <summary>
    /// UI Follow   mouse 
    /// </summary>
    /// <param name="eventData"></param>
    public void OnDrag(PointerEventData eventData)
    {
        transform.position = Input.mousePosition;
    }
    /// <summary>
    ///  Drag end 
    /// </summary>
    public void OnEndDrag(PointerEventData eventData)
    {
         // Get items that may exist at the end of the mouse 
         GameObject go = eventData.pointerCurrentRaycast.gameObject;
        if (go != null)// The position of the landing point is not empty 
        {
            Debug.Log(go.name);// Print a drop point location name 
            if (go.tag == ("Gird"))// The end position of the mouse is an empty grid 
            {
                Debug.Log(" Empty grid ");
                SetParentAndPosition(transform, go.transform);
            }
            else if (go.tag == transform.tag)// The label is the same   Put back 
            {
                // Drag items 1 Put it under the end of the mouse 
                SetParentAndPosition(transform, go.transform);
            }
            else// Invalid location , The item returns to its original position 
            {
                SetParentAndPosition(transform, nowparent);
            }
        }
        else
        {
            SetParentAndPosition(transform, nowparent);
        }
        isRaycastLocationValid = true;// Rays cannot penetrate objects 
    }
    //  take child Put it in parent Make its sub object 
    private void SetParentAndPosition(Transform child, Transform parent)
    {
        child.SetParent(parent);
        child.position = parent.position;// The coordinates of the child object follow those of the parent object 
    }
    public bool IsRaycastLocationValid(Vector2 sp, Camera eventCamera)
    {
        return isRaycastLocationValid;
    }
}