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

public class WuXianGunDong : MonoBehaviour
{
    List<string> strs = new List<string>();//需要修改

    public int DataTips;

    public Transform content;
    public GameObject loopItemPrefab;

    Vector3[] viewCorners = new Vector3[4];
    float hight;  //生成的loopItem所占的區(qū)域
    int current = -1;
    int itemCount;//生成的Item的數(shù)量

    public LinkedList<GameObject> loopItems = new LinkedList<GameObject>();

    #region 回調(diào)
    private void Awake()
    {
        for (int i = 0; i < DataTips; i++)
        {
            strs.Add(i.ToString());
        }

        hight = loopItemPrefab.GetComponent<RectTransform>().sizeDelta.y + content.GetComponent<VerticalLayoutGroup>().spacing;

        itemCount = (int)(transform.GetComponent<RectTransform>().sizeDelta.y / hight) + 2;

        if (itemCount > DataTips)
            itemCount = DataTips;
        for (int i = 0; i < itemCount; i++)
        {
            GameObject obj = Instantiate(loopItemPrefab, content);
            obj.GetComponentInChildren<Text>().text = strs[i];
            loopItems.AddLast(obj);
            current++;
        }
        transform.GetComponent<RectTransform>().GetWorldCorners(viewCorners);
        content.GetComponent<VerticalLayoutGroup>().enabled = true;
    }

    private void Start()
    {
        Invoke("DisGrid", 0.1f);
    }
    #endregion

    #region 拖拽的時候
    public void OnChange()
    {
        if (DataTips < itemCount)
        {
            return;
        }
        Vector3[] rectCorners = new Vector3[4];
        //當?shù)谝粋€離開視野的時候
        loopItems.First.Value.GetComponent<RectTransform>().GetWorldCorners(rectCorners);
        if (rectCorners[0].y > viewCorners[1].y)
        {
            if (current + 1 < strs.Count)
            {
                current++;
                loopItems.First.Value.transform.GetComponentInChildren<Text>().text = strs[current];
                loopItems.First.Value.GetComponent<RectTransform>().localPosition = loopItems.Last.Value.GetComponent<RectTransform>().localPosition - new Vector3(0, hight, 0);
                loopItems.AddLast(loopItems.First.Value);
                loopItems.RemoveFirst();
            }
        }
        //當最后一個進入視野的時候
        loopItems.First.Value.GetComponent<RectTransform>().GetWorldCorners(rectCorners);
        if (rectCorners[1].y < viewCorners[1].y)
        {
            if (current - itemCount >= 0)
            {
                loopItems.Last.Value.transform.GetChild(0).GetComponent<Text>().text = strs[current - itemCount];
                loopItems.Last.Value.GetComponent<RectTransform>().localPosition = loopItems.First.Value.GetComponent<RectTransform>().localPosition + new Vector3(0, hight, 0);
                loopItems.AddFirst(loopItems.Last.Value);
                loopItems.RemoveLast();
                current--;
            }
        }
    }
    #endregion

    public void DisGrid()
    {
        //關(guān)閉LayoutGroup
        content.GetComponent<VerticalLayoutGroup>().enabled = false;
        //設(shè)置寬度
        content.GetComponent<RectTransform>().sizeDelta = new Vector2(content.GetComponent<RectTransform>().sizeDelta.x, strs.Count * hight);
    }
}