1.UGUI自帶的Dropdown,建立之後,執行場景預設選擇第一個選項,再次點選第一個選項也不會觸發,因專案需求,所以要改成多次點選有效

2.建立下拉框(Dropdown),建立好之後刪除Dropdown元件

3.建立c#指令碼 (重寫下拉框,新增一個bool變數用來控制)

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

public class DropdownEx : Dropdown
{
    
 
public bool m_AlwaysCallback = false;
    public  void  ShowController()
    {
        base.Show();
        Transform toggleRoot = transform.Find("Dropdown List/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;
            temp.onValueChanged.AddListener(x => OnSelectItemEx(temp));
        }
    }

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

    
 
public void OnSelectItemEx(Toggle toggle)
    {
        if (!toggle.isOn)
        {
            toggle.isOn = true;
            return;
        }

        int selectedIndex = -1;
        Transform tr = toggle.transform;
        Transform parent = tr.parent;
        for (int i = 0; i < parent.childCount; i++)
        {
            if (parent.GetChild(i) == tr)
            {
                // Subtract one to account for template child.
                selectedIndex = i - 1;
                break;
            }
        }

        if (selectedIndex < 0)
            return;
        if (value == selectedIndex && m_AlwaysCallback)
            onValueChanged.Invoke(value);
        else
            value = selectedIndex;
        Hide();
    }
}

4.把指令碼新增到下拉框上面會出現新的元件(如下圖所示)

箭頭處需要自己拖上去

5.建立一個Editor指令碼放在Editor資料夾下

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEditor;
using UnityEditor.UI;
[CustomEditor(typeof(DropdownEx), true)]
[CanEditMultipleObjects]
public class DropdowmExEditor : DropdownEditor
{
    SerializedProperty m_AlwaysCallback;
    protected override void OnEnable()
    {
        base.OnEnable();
        m_AlwaysCallback = serializedObject.FindProperty("m_AlwaysCallback");
    }

    public override void OnInspectorGUI()
    {
        base.OnInspectorGUI();
        EditorGUILayout.PropertyField(m_AlwaysCallback);
        serializedObject.ApplyModifiedProperties();
    }
}

需要重複點選就勾選上m_AlwaysCallback變數

❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤

❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤

❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤