unity UGUI动态滑动列表

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

public class SceneMail : MonoBehaviour
{
    public Button mItemPrefab;//要添加到列表的预设体按钮组件
    public Transform mContentTransform;//容器Content的transform
    public Scrollbar mScrollbar;//滑动条

    List<Button> lists = new List<Button>();//存放按钮组件
    
    float itemHeight;//单个按钮组件的height

    RectTransform rect;//容器content的rect

    public VerticalLayoutGroup group;//用于计算内容的高度

    // Use this for initialization
    void Start()
    {
        rect = mContentTransform.GetComponent<RectTransform>();
        itemHeight = mItemPrefab.GetComponent<RectTransform>().rect.height;
        

        ShowItems();
        mScrollbar.value = 1.0f;

    }

    /// <summary>
    /// 显示Item列表
    /// </summary>
    void ShowItems()
    {
        for (int i = 0; i < 20; i++)
        {
            AddItem();
        }
    }
    void Update()
    {
        //添加
        if (Input.GetKeyDown(KeyCode.Alpha0))
        {
            AddItem();
        }
        //使列表跳转到顶部
        if (Input.GetKeyDown(KeyCode.Alpha1))
        {
            ToTopFunc();
        }
        //清空列表
        if (Input.GetKeyDown(KeyCode.Alpha2))
        {
            ClearFunc();
        }
    }
    //添加组件
    void AddItem()
    {
        
        Button item = Instantiate(mItemPrefab, transform.position, transform.rotation);
        item.GetComponentInChildren<Text>().text = lists.Count.ToString();
        item.transform.parent = mContentTransform;
        lists.Add(item);

        //给每个按钮组件监听点击事件
        item.onClick.AddListener(
            () =>
            {
                onClickFunc(item);
            }
        );

        //rect.sizeDelta的x是width 
        //rect.sizeDelta的y是height
        //rect.sizeDelta=new Vector2(rect.sizeDelta.x, lists.Count * itemHeight);
        rect.sizeDelta = new Vector2(rect.sizeDelta.x,
            group.padding.top + group.padding.bottom + lists.Count * itemHeight + (lists.Count - 1) * group.spacing);
        //rect.sizeDelta = new Vector2(rect.sizeDelta.x, lists.Count * itemHeight);
    }
    //使列表跳转到顶部
    void ToTopFunc()
    {
        
        //offsetMin 是vector2(left, bottom);

        //offsetMax 是vector2(right, top);

        rect.offsetMin = new Vector2(rect.offsetMin.x,-rect.sizeDelta.y);
        rect.offsetMax = new Vector2(rect.offsetMax.x,0);

        
    }
    //使列表跳转到底部
    void ToBottomFunc()
    {
        
        /*rect.offsetMin = new Vector2(rect.offsetMin.x, 0);
        rect.offsetMax = new Vector2(rect.offsetMax.x, rect.sizeDelta.y);*/
    }
    void onClickFunc(Button btn)
    {
        Debug.Log(btn.gameObject.GetComponent<Text>());
        removeItemFunc(btn);
    }
    //清空列表
    void ClearFunc()
    {
        for(int i = 0; i < lists.Count; i++)
        {
            Destroy(lists[i].gameObject);
        }
        lists = new List<Button>();
        rect.sizeDelta = new Vector2(rect.sizeDelta.x, lists.Count * itemHeight);
    }
    //删除单个按钮组件
    void removeItemFunc(Button _btn)
    {
        //因为Vertical Layout Group组件会自动排列添加上的控件，所以只需要移除场景中的物体模型和list中对象就行了
        //排列位置的任务就交给Vertical Layout Group 了

        Destroy(_btn.gameObject);

        int index = lists.IndexOf(_btn);
        lists.Remove(_btn);

        Debug.Log(lists.Count);

        //需要重置容器的height
        rect.sizeDelta = new Vector2(rect.sizeDelta.x,
            group.padding.top + group.padding.bottom + lists.Count * itemHeight + (lists.Count - 1) * group.spacing);

        //rect.sizeDelta = new Vector2(rect.sizeDelta.x, lists.Count * itemHeight);
        
        /*
        if (rect.sizeDelta.y > 1080)
        {
            
            rect.sizeDelta = new Vector2(rect.sizeDelta.x, lists.Count * itemHeight);
        }
        else
        {
            rect.sizeDelta = new Vector2(rect.sizeDelta.x, 1080);
        }*/



    }
}