UGUI 下拉滚动框

开始制作好友系统了, 发现有一个UI跟QQ的面板一模一样. 于是就写了一个公共的下拉滚动框.需要把按钮的中心点(pivot.y = 1),描点为最上方 直接上图吧

代码如下:

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

public class DropScroll : MonoBehaviour {

    [SerializeField]
    private Button[] btnList;               //提供多个按钮
    private RectTransform thisRT;

    [SerializeField]
    private GameObject scrollViewTmp;       //提供一个滚动视图模版
    private List<RectTransform> scrollViewList = new List<RectTransform>(); 

    public void Start() 
    {
        Init();
    }

    public void Init() 
    {
        RectTransform rt = null;

        foreach (var btn in btnList)
        {
            EventTriggerListener.Get(btn.gameObject).OnClick += BtnDropClickEvent;
            rt = GameObject.Instantiate(scrollViewTmp).GetComponent<RectTransform>();
            scrollViewList.Add(rt);
            rt.gameObject.SetActive(false);
            rt.transform.SetParent(this.transform,false);
        }

        thisRT = this.GetComponent<RectTransform>();
    }

    private void BtnDropClickEvent(GameObject go) 
    {
        RectTransform rt = go.GetComponent<RectTransform>();
        RectTransform btnRt = null;
        float height = thisRT.sizeDelta.y;
        int index = rt.GetSiblingIndex();

        HideAllScrollView();
        scrollViewList[index].sizeDelta = new Vector2(thisRT.sizeDelta.x, height - btnList.Length * rt.sizeDelta.y);
        scrollViewList[index].anchoredPosition = new Vector2(0, -((index + 1) * rt.sizeDelta.y));
        scrollViewList[index].gameObject.SetActive(true);

        for (int i = 0; i < btnList.Length; i++)
        {
            btnRt = btnList[i].GetComponent<RectTransform>();
            if (i > index)
            {
                btnRt.anchoredPosition = new Vector2(btnRt.anchoredPosition.x, -height + ((btnList.Length - i) * btnRt.sizeDelta.y));
            }
            else 
            {
                btnRt.anchoredPosition = new Vector2(btnRt.anchoredPosition.x, -(i * btnRt.sizeDelta.y));
            }
        }
    }

    
    private void HideAllScrollView() 
    {
        for (int i = 0; i < scrollViewList.Count; i++)
        {
            scrollViewList[i].gameObject.SetActive(false);
        }
    }
}

public class EventTriggerListener : UnityEngine.EventSystems.EventTrigger 
{
    public delegate void VoidDelegate(GameObject go);
    public event VoidDelegate OnClick;

    static public EventTriggerListener Get(GameObject go)
    {
        EventTriggerListener listener = go.GetComponent<EventTriggerListener>();
        
        if (listener == null) 
            listener = go.AddComponent<EventTriggerListener>();

        return listener;
    }

    public override void OnPointerClick(PointerEventData eventData)
    {
        if (OnClick != null)
            OnClick(gameObject);
    }
}

层次图: