Unity 实现简单的无限循环ScrollView

    反正实现的效果就是如标题所示了，无限循环的scrollView。注意这里的方法是比较粗浅的，也当抛砖引玉。反正效果是实现了，然后性能也还行。
   先看效果：

    之所以要实现这种效果，主要是因为scrollview底下的内容量有时候可能会非常的多，比如说物品背包栏，可能包含成千上万个物品。直接使用原生scrollview的话，那性能消耗是蛮夸张的。毕竟屏幕里能显示的内容数量就那么几个，但是却吃那么多的性能多少有点怪。解决这种情况的方法，一种是无限scrollview，就是再显示区域外再多提供两个格子，一个为头部，一个为尾部，不停的调换位置就行了。 另外一种就是分页了，就提供固定几个格子，然后按照分页修改格子的内容。
   代码分两个部分，一个与scrollview相关，一个与scrollbar相关。具体的代码分析实在是写的头痛，有需要的话自己看看就行了。不是什么很难的东西。
   下边的scrollview的代码：
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
public class UnlimitedScrollView : MonoBehaviour, IEndDragHandler
{
    [Header("内容条目的数量")]
    public int ItemNum;
    [Header("Item高度间隔")]
    public int ItemSizeHight;



    private RectTransform Content;


    private RectTransform[] ShowItem;//Item数组


    public Scrollbar VerticalScrollbar;

    private float CurrentContentPos;
    private int CurrentItemNum;
    private int _Downcurrentiemnum;

    private int Head, End;

    private float viewHight;


    [Header("当前显示的数目")]

    private int ShowItemNum;


    [Header("Item的obj")]
    public GameObject ShowItemObj;


    // Start is called before the first frame update
    void Start()
    {
        Content = this.GetComponent<ScrollRect>().content;
        float ItemHight = ShowItemObj.GetComponent<RectTransform>().sizeDelta.y;
        viewHight = this.GetComponent<RectTransform>().sizeDelta.y;

        ItemSizeHight = (int)(ItemSizeHight + ItemHight);

        ShowItemNum = (int)(viewHight / ItemSizeHight) + 3;//竖向显示的数目



        float ContentHight = ItemSizeHight * ItemNum;
        Content.GetComponent<RectTransform>().sizeDelta = new Vector2(Content.sizeDelta.x, ContentHight);

        CurrentItemNum = 1;
        _Downcurrentiemnum = CurrentItemNum;

        Init();
        CheckItemAndSet();


        Head = 0;
        End = ShowItem.Length - 1;


        if (VerticalScrollbar != null)
        {
            VerticalScrollbar.onValueChanged.AddListener((float a) => { CheckItemAndSet(); });
            VerticalScrollbar.gameObject.AddComponent<MyScrollbar>();
            VerticalScrollbar.gameObject.GetComponent<MyScrollbar>().EndDrag.AddListener(() => { CheckItemAndSet(); } );
        }//检测有无scrollbar



    }

    // Update is called once per frame
    void Update()
    {
        CurrentContentPos = Content.anchoredPosition.y - (ItemSizeHight / 2);
        CheckItem();

        if (CurrentItemNum >= _Downcurrentiemnum + 1)
        {
            _Downcurrentiemnum = CurrentItemNum;
            SwapHeadToEnd();
        }
        else if (CurrentItemNum <= _Downcurrentiemnum - 1)
        {

            _Downcurrentiemnum = CurrentItemNum;
            SwapEndToHead();
        }


    }

    public void Init()
    {
        ShowItem = new RectTransform[ShowItemNum];



        ShowItem[0] = ShowItemObj.GetComponent<RectTransform>();

        for (int i = 0; i < ShowItemNum; i++)
        {



            GameObject showitemobj = GameObject.Instantiate(ShowItemObj, Content, false);
            ShowItem[i] = showitemobj.GetComponent<RectTransform>();
            showitemobj.name = ShowItemObj.name + i;
            showitemobj.GetComponent<RectTransform>().anchoredPosition = new Vector2(showitemobj.GetComponent<RectTransform>().anchoredPosition.x, -(i) * ItemSizeHight);

        }
        ShowItemObj.SetActive(false);
    }

    public void CheckItem()
    {
        CurrentItemNum = (int)(CurrentContentPos / ItemSizeHight);//当前应该显示的数
    }

    public void SwapHeadToEnd()
    {
        ShowItem[Head].anchoredPosition = new Vector2(ShowItem[Head].anchoredPosition.x, ShowItem[End].anchoredPosition.y - ItemSizeHight);
        ShowItem[Head].transform.SetAsLastSibling();

        //  ShowItem[Head].GetComponentInChildren<Text>().text = (CurrentItemNum + ShowItem.Length - 1).ToString();
        End = Head;
        Head++;



        if (Head == ShowItem.Length)
        {
            Head = 0;

        }


    }//把头部挪到尾部
    public void SwapEndToHead()
    {

        ShowItem[End].anchoredPosition = new Vector2(ShowItem[End].anchoredPosition.x, ShowItem[Head].anchoredPosition.y + ItemSizeHight);
        ShowItem[End].transform.SetAsFirstSibling();
        //  ShowItem[End].GetComponentInChildren<Text>().text = CurrentItemNum.ToString();
        Head = End;
        End--;


        if (End == -1)
        {
            End = ShowItem.Length - 1;

        }


    }//把尾部挪到头部

    public void CheckItemAndSet()
    {
        if (ShowItem[Head].anchoredPosition.y != CurrentItemNum * ItemSizeHight + (ItemSizeHight / 2))
        {
            int _currentitemnum = CurrentItemNum;
            int _head = Head;
            for (int i = 0; i < ShowItem.Length; i++)
            {
                //    ShowItem[_head].GetComponentInChildren<Text>().text = _currentitemnum.ToString();
                ShowItem[_head].anchoredPosition = new Vector2(ShowItem[_head].anchoredPosition.x, -_currentitemnum * ItemSizeHight + (ItemSizeHight / 2));
                _head++;
                if (_head == ShowItem.Length)
                {
                    _head = 0;
                }
                _currentitemnum++;
            }
        }



    }//检查一遍当前的item对应位置，错误的话便重新排序位置，并再次赋值



    public void OnEndDrag(PointerEventData eventData)
    {
        CheckItemAndSet();
    }




}

然后是一个scrollbar的代码，就是提供一个监听结束拖拽的事件：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.Events;
public class DoEventCall : UnityEvent { }
public class MyScrollbar : MonoBehaviour,IEndDragHandler
{
    public DoEventCall EndDrag = new DoEventCall();
    public void OnEndDrag(PointerEventData eventData)
    {
        EndDrag.Invoke();

    }


}