UGUI实现ScrollView无限滚动效果

public class UIScrollViewTest : MonoBehaviour {
 
  public RectTransform content;
  public GameObject cell;
  // cell的初始化个数
  public int cellAmount = 0;
  // 鼠标上滑时，存储Cell的Queue。正序存储
  public Queue F_cellQuee = new Queue();
  // 鼠标下滑时，存储Cell的Queue。到序存储
  public Queue B_cellQuee = new Queue();
  // cell的Size
  public Vector2 cellSize = new Vector2(100,100);
  // cell的间隔
  public Vector2 cellOffset = new Vector2(0,0);
  // 列数
  public int columnCount = 0;
  private int rowCount;
  // 上一次content的位置
  public float lastPos;
  // 滚动的次数
  public int loopCount = 0;
  // cell显示的数据段的开头和结尾序号
  public int HeadNum = 0;
  public int TailNum;
 
  public Sprite[] sp;
  public List<Sprite> data;
 
 
  void Start()
  {
    for (int i = 0; i < sp.Length; i++)
    {
      data.Add(sp[i]);
    }
 
    InitialScrollView(data);
    TailNum = cellAmount-1;
    lastPos = content.localPosition.y;
    //Debug.LogError("行数是：：：" + rowCount);
 
    //Debug.LogError("+++++++++++++++++  " + (5>>3));
  }
 
 
  void Update()
  {
    // 触发滚动。
    if (content.localPosition.y - lastPos > cellSize.y && data.Count - cellAmount - loopCount*columnCount >0)
    {
      //Debug.LogError("11111111111  " + (data.Count - cellAmount - loopCount * columnCount));
      LoopScrolView(data);
      lastPos = content.localPosition.y;
    }
  }
 
 
  
  
  // 初始化cell
  void InitialScrollView(List<Sprite> data)
  {
    for (int i = 0; i < cellAmount; i++)
    {
      GameObject obj = Instantiate(cell.gameObject);
      obj.transform.SetParent(content);
      obj.name = "cell0" + i.ToString();
      obj.transform.GetChild(0).GetComponent<Text>().text = "cell0"+i.ToString();
      // 显示默认的数据
      obj.GetComponent<Image>().sprite = data[i];
    }
    // 初始化Queue
    for (int i = content.childCount-1; i >= 0; i--)
    {
      B_cellQuee.Enqueue(content.GetChild(i).gameObject);
    }
    for (int i = 0; i < content.childCount; i++)
    {
      F_cellQuee.Enqueue(content.GetChild(i).gameObject);
    }
 
    // 计算行数
    if (cellAmount % columnCount >0)
    {
      rowCount = cellAmount / columnCount + 1;
    } else {
      rowCount = cellAmount / columnCount;
    }
 
    // 排列cell的位置
    int index = 0;
    for (int r = 1; r <= rowCount; r++)
    {
      for (int c = 1; c <= columnCount; c++)
      {
        if (index < cellAmount)
        {
          Vector2 pos = new Vector2(cellSize.x / 2 + (cellSize.x + cellOffset.x) * (c-1), -cellSize.y / 2 - (cellOffset.y + cellSize.y) * (r-1));
          content.GetChild(index).GetComponent<RectTransform>().SetInsetAndSizeFromParentEdge(RectTransform.Edge.Top, 0, 100);
          content.GetChild(index).GetComponent<RectTransform>().SetInsetAndSizeFromParentEdge(RectTransform.Edge.Left, 0, 100);
          content.GetChild(index).GetComponent<RectTransform>().anchoredPosition = pos;
          index++;
        }
      }
    }
 
    Vector2 v = content.sizeDelta;
    // 初始化content的size
    content.sizeDelta = new Vector2(v.x, rowCount * cellSize.y + cellOffset.y*(rowCount-1));
  }
 
 
  /// 保持content的大小，这里是保持大小为在cell的行数基础上，向下多出bottomCount行的距离
  void SetContentSize(int upperCount, int bottomCount)
  {
    if (content.sizeDelta != new Vector2(content.sizeDelta.x, content.sizeDelta.y + bottomCount * (cellSize.y + cellOffset.y)))
    {
      content.sizeDelta = new Vector2(content.sizeDelta.x, content.sizeDelta.y + bottomCount*(cellSize.y + cellOffset.y));
    }
  }
 
  // 计算顶部的Cell轮换到底部时的位置。以当前最后一行的最后一个Cell的位置为基准计算。
  void SetBottomCellPosition(int index, RectTransform rect, Vector2 pos)
  {
    Vector2 v = Vector2.zero;
    if (cellAmount % columnCount == 0) // 整除。每一行都满的情况。
    {
      float x = pos.x - cellSize.x * (columnCount - index-1) - cellOffset.x * (columnCount-index-1);
      float y = pos.y - cellSize.y - cellOffset.y;
      v = new Vector2(x,y);
    }
    // 出现不满行的情况。例如数据有103个，可以用23个cell来轮换。这样就会出现不满行的情况。
    // 这种情况下是顶部的一行cell顺次接到底部不满的行。例如23号cell后面接1号和2号cell，3号和4号cell填充到第“7”行
    else if (cellAmount % columnCount + index+1<=columnCount) 
    {
      float x = pos.x + cellSize.x * (index+1) + cellOffset.x * (index+1);
      float y = pos.y;
      v = new Vector2(x, y);
    }
    else
    {
      float x = pos.x - cellSize.x * (columnCount - index-1) - cellOffset.x * (columnCount - index-1);
      float y = pos.y - cellSize.y - cellOffset.y;
      v = new Vector2(x, y);
    }
    //Debug.LogError("++++++++++++++  " + pos+ "         "+ v);
    rect.anchoredPosition = v;
    rect.SetAsLastSibling();
  }
 
  // 计算底部的cell轮换到顶部是的位置，基准位置是当前行的第一个cell。
  void SetUpperCellPosition(int index, RectTransform rect, Vector2 pos)
  {
    Vector2 v = Vector2.zero;
    if (cellAmount % columnCount == 0) // 整除
    {
      float x = pos.x + cellSize.x * index + cellOffset.x * index;
      float y = pos.y + cellSize.y + cellOffset.y;
      v = new Vector2(x, y);
    }
    //else if (cellAmount % columnCount + index + 1 <= columnCount)
    //{
    //  float x = pos.x + cellSize.x * (index + 1) + cellOffset.x * (index + 1);
    //  float y = pos.y;
    //  v = new Vector2(x, y);
    //}
    //else
    //{
    //  float x = pos.x - cellSize.x * (columnCount - index - 1) - cellOffset.x * (columnCount - index - 1);
    //  float y = pos.y - cellSize.y - cellOffset.y;
    //  v = new Vector2(x, y);
    //}
    //Debug.LogError("++++++++++++++  " + pos+ "         "+ v);
    rect.anchoredPosition = v;
    rect.SetAsFirstSibling();
  }
 
 
  // 鼠标上滑时，显示当前cell的数据。同时记录数据段的序号递增。
  void ShowRestCellData(Image cell, int index)
  {
    if (TailNum< data.Count-1)
    {
      Debug.LogError("当前的序号是：：：：" + TailNum);
      TailNum++;
      HeadNum++;
      cell.sprite = data[TailNum];
    }
  }
 
  void ShowPreviousCellData(Image cell, int index)
  {
    if (HeadNum > 0)
    {
      Debug.LogError("当前的序号是：：：：" + HeadNum);
      TailNum--;
      HeadNum--;
      cell.sprite = data[HeadNum];
    }
  }
 
 
  // 轮换的函数。每次乱换一行的cell。
  void LoopScrolView(List<Sprite> data)
  {
    SetContentSize(0, 1);
    loopCount++;
    RectTransform rect2 = content.GetChild(content.childCount - 1).GetComponent<RectTransform>();
    for (int i = 0; i < columnCount; i++)
    {
      GameObject obj = F_cellQuee.Dequeue() as GameObject;
      RectTransform rect = obj.GetComponent<RectTransform>();
      ShowRestCellData(obj.GetComponent<Image>(), i);
      SetBottomCellPosition(i, rect, rect2.anchoredPosition);
      F_cellQuee.Enqueue(obj);
    }
  }
 
}