目前是只写了垂直排列的算法，水平的还没写（原理一样，懒得写了，有需求在说）
特点：
1.支持NGUI的ScrollView进行循环滚动(该脚本挂在UIScrollView下)
2.支持每个单元格有不同的大小
3.支持Scrollbar
4.可运用于NGUI3.9.4(亲测)，其他版本不知道

Dingtalk_20210823162645.jpg

using System;
using System.Collections.Generic;
using UnityEngine;
public class NguiInfiniteScrollView : MonoBehaviour
{
    //可见区域cell列表（当前激活的Cell）
    Dictionary<int,NguiInfiniteScrollViewCell> cellDatas = new Dictionary<int,NguiInfiniteScrollViewCell>();

    //缓冲Cell
    Queue<NguiInfiniteScrollViewCell> cellDatasCache = new Queue<NguiInfiniteScrollViewCell>();

    //第一个和最后一个物体
    private NguiInfiniteScrollViewCell firstCell;
    private NguiInfiniteScrollViewCell LastCell;

    //第一个和最后一个缓冲物体
    private NguiInfiniteScrollViewCell firstCacheCell;
    private NguiInfiniteScrollViewCell LastCacheCell;

    //要实例化的预制体
    public GameObject Prefab;

    private UIScrollView scrollView;
    private UIPanel panel;

    //ScrollView组件下的子物体，用于预制体生成时作为父对象
    public UIWidget Hold;

    //目前只判定Horizontal和Vertical 
    private bool posXorY;
    private float panelOffset
    {
        get
        {
            if (posXorY)
                return panel.clipOffset.x;
            else
                return panel.clipOffset.y;
        }
    }

    //物体坐标
    private Vector3 _cellSizeVector3 = Vector3.zero;
    private  float SetcellSizeVector3
    {
        set
        {
            if (posXorY)
                _cellSizeVector3.x = value;
            else
                _cellSizeVector3.y = value;
        }
    }

    //UIPanel初始偏移
    private float initoffset;

    //ScrollView初始坐标
    private float initTransform;

    //UIPanel当前滚动区域大小
    private float scrollClipArea;

    //滚动区域总大小
    private float sizeCount;

    //数据总数
    private int _dataCount;

    //更新Cell
    private Action<NguiInfiniteScrollViewCell> _updataCallBack;

    //根据index获取大小
    private Func<int, float> _getDataSizeCallBack;
    
    //获取数据总的Size大小
    private void SetSizeCount()
    {
        float sizeSum = 0;
        for (int i = 0; i < _dataCount; i++)
        {
            sizeSum += _getDataSizeCallBack(i);
        }
        sizeCount = sizeSum;

        Hold.height = (int)sizeCount;
    }
    
    //初始化后刷新一下
    [HideInInspector]public bool isLoad = false;//用于判定是否初始化过
    bool isfirst;//判定是否是第一次初始化
    private void LateUpdate()
    {
        if(isLoad&&!isfirst)
        {
            isfirst = true;
            scrollView.ResetPosition();
            initoffset = posXorY ? panel.clipOffset.x : panel.clipOffset.y;
            initoffset = Math.Abs(initoffset);
            initTransform = transform.localPosition.y;
            panel.onClipMove += LoadLastCell;
            panel.onClipMove += LoadFirstCell;
        }
        
    }

    public void ReLoadData(int count, Action<NguiInfiniteScrollViewCell> updataCallBack = null, Func<int, float> getCellSizeCallback = null)
    {
        _dataCount = count;

        if (updataCallBack != null)
            _updataCallBack = updataCallBack;
        if (getCellSizeCallback != null)
            _getDataSizeCallBack = getCellSizeCallback;

        SetSizeCount();
        foreach (var item in cellDatas)
        {
            item.Value.Cellprefab.gameObject.SetActive(false);
            cellDatasCache.Enqueue(item.Value);
        }
        cellDatas.Clear();
        initLoad();
        scrollView.ResetPosition();
    }
    public void JumpTo(int index)
    {
        float sizeSum = 0;
        for (int i = 0; i < index; i++)
        {
            sizeSum += _getDataSizeCallBack(i);
        }
        scrollView.verticalScrollBar.value = sizeSum / sizeCount;
    }
    public NguiInfiniteScrollViewCell GetItemByDataIndex(int index)
    {
        cellDatas.TryGetValue(index, out NguiInfiniteScrollViewCell obj);
        return obj;
    }
    public void init(int dataCount, Action<NguiInfiniteScrollViewCell> updataCallBack = null,Func<int,float> getCellSizeCallback = null)
    {
        _dataCount = dataCount;
        _updataCallBack = updataCallBack;
        _getDataSizeCallBack = getCellSizeCallback;
        scrollView = GetComponent<UIScrollView>();
        panel = GetComponent<UIPanel>();
        posXorY = scrollView.movement == UIScrollView.Movement.Horizontal;
        Prefab.GetComponent<UIWidget>().pivot = posXorY ? UIWidget.Pivot.Left : UIWidget.Pivot.Top;
        initLoad();
        isLoad = true;
    }
    //获取缓冲Cell
    private NguiInfiniteScrollViewCell GetFreeCell()
    {
        NguiInfiniteScrollViewCell cellCache = null;
        
        if(cellDatasCache.Count==0)
        {
            GameObject prefab = Instantiate(Prefab, Hold.transform);
            cellCache = new NguiInfiniteScrollViewCell(prefab, 0);
        }
        else
        {
            cellCache = cellDatasCache.Dequeue();
        }
        return cellCache;
    }
    
    private void initLoad()
    {
        int Index = 0;
        //初始化区域总长度
        float AreaCellSizeCount = 0;
        //初始化生成数量
        int CreateCount = 0;
        scrollClipArea = posXorY ? panel.finalClipRegion.z : panel.finalClipRegion.w;
        while (AreaCellSizeCount < scrollClipArea && CreateCount < _dataCount)
        {

            GameObject prefab = null;
            NguiInfiniteScrollViewCell cell = null;
            if (cellDatasCache.Count==0)
            {
                 prefab = Instantiate(Prefab, Hold.transform);
                 cell = new NguiInfiniteScrollViewCell(prefab, Index++);
            }else
            {
                cell = cellDatasCache.Dequeue();
                cell.Cellprefab.SetActive(true);
                cell.dataIndex = Index++;
                prefab = cell.Cellprefab;
            }
            cellDatas.Add(cell.dataIndex,cell);
            
            //坐标运算
            SetcellSizeVector3 = posXorY? AreaCellSizeCount : -AreaCellSizeCount;
            prefab.transform.localPosition =  _cellSizeVector3;
            AreaCellSizeCount += _getDataSizeCallBack(CreateCount);
            cell.SetSize(posXorY, (int)_getDataSizeCallBack(CreateCount));

            CreateCount++;
            _updataCallBack?.Invoke(cell);
        }
        firstCell = cellDatas[0];
        LastCell = cellDatas.Count > 1 ? cellDatas[Index-1] : firstCell;
        //默认加载2个缓冲cell
        if (cellDatasCache.Count < 2)
        {
            int cacheCount = cellDatasCache.Count;
            for (int i = cacheCount; i < 2; i++)
            {
                GameObject prefab = Instantiate(Prefab, Hold.transform);
                NguiInfiniteScrollViewCell cell = new NguiInfiniteScrollViewCell(prefab, 0);
                cellDatasCache.Enqueue(cell);
                prefab.gameObject.SetActive(false);
            }
        }
    }
    void Update()
    {
      //  LoadLastCell();
     //   LoadFirstCell();
    }
    private void LoadFirstCell(UIPanel panel)
    {
       
        //不是第一个数据并且first缓存可用
        while (firstCell.dataIndex != 0 &&panelOffset- (-initoffset / 2)- firstCell.Cellprefab.transform.localPosition.y>-firstCell.Size*0.5f)
        {

            //回收最后一个
            if (initoffset / 2 - panelOffset + LastCell.Cellprefab.transform.localPosition.y < -LastCell.Size * 1.5)
            {
                LastCell.Cellprefab.SetActive(false);
                cellDatasCache.Enqueue(LastCell);
                cellDatas.Remove(LastCell.dataIndex);
                LastCell = cellDatas[LastCell.dataIndex - 1];
            }

            firstCacheCell = GetFreeCell();

            int dataindex = firstCell.dataIndex - 1;
            firstCacheCell.Cellprefab.SetActive(true);
            float cellSize = _getDataSizeCallBack(dataindex);

            SetcellSizeVector3 = cellSize;

            firstCacheCell.SetSize(posXorY, (int)cellSize);

            if (posXorY)
                firstCacheCell.Cellprefab.transform.localPosition = firstCell.Cellprefab.transform.localPosition - _cellSizeVector3;
            else
                firstCacheCell.Cellprefab.transform.localPosition = firstCell.Cellprefab.transform.localPosition + _cellSizeVector3;

            firstCacheCell.dataIndex = dataindex;

            cellDatas.Add(firstCacheCell.dataIndex,firstCacheCell);
            _updataCallBack?.Invoke(firstCacheCell);

            firstCell = firstCacheCell;
        }

    }
    private void LoadLastCell(UIPanel panel)
    {
       
        //最后一个已经完全加载
        while (LastCell.dataIndex != _dataCount - 1 && initoffset/2 - panelOffset + LastCell.Cellprefab.transform.localPosition.y > LastCell.Size*0.5)
        {

            //第一个单元格往上超出视野
            if (panelOffset - (-initoffset / 2) - firstCell.Cellprefab.transform.localPosition.y < -firstCell.Size * 1.5)
            {
                firstCell.Cellprefab.SetActive(false);
                cellDatasCache.Enqueue(firstCell);
                cellDatas.Remove(firstCell.dataIndex);
                firstCell = cellDatas[firstCell.dataIndex + 1];
            }

            LastCacheCell = GetFreeCell();
            int dataindex = LastCell.dataIndex + 1;
            LastCacheCell.Cellprefab.SetActive(true);

            float cellSize = _getDataSizeCallBack(dataindex);

            SetcellSizeVector3 = LastCell.Size;
            LastCacheCell.SetSize(posXorY, (int)cellSize);

            if (posXorY)
                LastCacheCell.Cellprefab.transform.localPosition = LastCell.Cellprefab.transform.localPosition + _cellSizeVector3;
            else
                LastCacheCell.Cellprefab.transform.localPosition = LastCell.Cellprefab.transform.localPosition - _cellSizeVector3;
            

            LastCacheCell.dataIndex = dataindex;
            
            cellDatas.Add(LastCacheCell.dataIndex, LastCacheCell);
            _updataCallBack?.Invoke(LastCacheCell);

            LastCell = LastCacheCell;
        }
    }
}

public class NguiInfiniteScrollViewCell
{
    //要生成的预制体
    public GameObject Cellprefab;
    //数据下标索引
    public int dataIndex;
    public float Size;
    public NguiInfiniteScrollViewCell(GameObject cellPrefab, int index)
    {
        Cellprefab = cellPrefab;
        dataIndex = index;
    }
    public void SetSize(bool isX,int size)
    {
        if (isX)
            Cellprefab.GetComponent<UIWidget>().width = size;
        else
            Cellprefab.GetComponent<UIWidget>().height = size;

        Size = size;
    }
}