MultipleSelection_Dropdown——Dropdown复选框扩展

 参考文章：

https://www.cnblogs.com/chinarbolg/p/9601417.html  

https://www.cnblogs.com/Fivee/p/13099362.html

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

public class MultipleSelection_Dropdown : Dropdown
{
    public bool AlwaysCallback = false;//是否开启 点击选项按钮总是回调

    // 当前筛选的技能质量标记
    private int SelectIndexBitMark = 0;

    public List<int> indexs = new List<int>();

    public new void Show()
    {
        base.Show();
        DropdownToggleEvent();
    }

    public void DropdownToggleEvent()
    {
        Transform toggleRoot = transform.Find("Dropdown List/Viewport/Content");
        //Transform toggleRoot = template.Find("Viewport/Content");
        Toggle[] toggleList = toggleRoot.GetComponentsInChildren<Toggle>(false);
        for (int i = 0; i < toggleList.Length; i++)
        {
            Toggle temp = toggleList[i];
            temp.onValueChanged.RemoveAllListeners();
            // temp.isOn = false;   // 原文
            //temp.SetIsOnWithoutNotify()
            temp.isOn = indexs.Contains(i); // 改造后
            //temp.isOn = ((1 << i) & SelectIndexBitMark) > 0; //第一次改造后原文
            temp.onValueChanged.AddListener(x => OnSelectItemEx(temp, x));
        }
        RefreshShownValue();
    }

    public override void OnPointerClick(PointerEventData eventData)
    {
        Show();
    }


    public void OnSelectItemEx(Toggle toggle, bool isOn)
    {

        int selectedIndex = -1;
        Transform tr = toggle.transform;
        Transform parent = tr.parent;
        for (int i = 0; i < parent.childCount; i++)
        {
            if (parent.GetChild(i) == tr)
            {
                selectedIndex = i - 1;
                break;
            }
        }

        if (selectedIndex < 0)
            return;
        if (value == selectedIndex && AlwaysCallback)
            onValueChanged?.Invoke(value);
        else
            value = selectedIndex;

        if (!isOn)
        {
            if (indexs.Contains(value))
                indexs.Remove(value);
            //toggle.isOn = true;
            //Debug.Log("value = " + value + "+ indexs.count =" + indexs.Count);
            //return;
            //SelectIndexBitMark -= SelectIndexBitMark & (1 << value);   // 新增
        }
        else
        {
            if (!indexs.Contains(value))
                indexs.Add(value);
            //SelectIndexBitMark |= 1 << value;   // 新增
        }
        Debug.Log("selectedIndex = " + string.Join(",", indexs));
        Hide();
        RefreshShownValue();
    }
}