【Unity】エディタ拡張で Add Component のようなドロップダウンメニューを実装できる「AdvancedDropdown」

使用例

using System;
using UnityEditor;
using UnityEditor.IMGUI.Controls;
using UnityEngine;

class WeekdaysDropdown : AdvancedDropdown
{
    public event Action<AdvancedDropdownItem> OnSelect;

    public WeekdaysDropdown( AdvancedDropdownState state ) : base( state )
    {
    }

    protected override AdvancedDropdownItem BuildRoot()
    {
        var root = new AdvancedDropdownItem( "Weekdays" );

        var firstHalf  = new AdvancedDropdownItem( "First half" );
        var secondHalf = new AdvancedDropdownItem( "Second half" );
        var weekend    = new AdvancedDropdownItem( "Weekend" );

        firstHalf.AddChild( new AdvancedDropdownItem( "Monday" ) );
        firstHalf.AddChild( new AdvancedDropdownItem( "Tuesday" ) );
        secondHalf.AddChild( new AdvancedDropdownItem( "Wednesday" ) );
        secondHalf.AddChild( new AdvancedDropdownItem( "Thursday" ) );
        weekend.AddChild( new AdvancedDropdownItem( "Friday" ) );
        weekend.AddChild( new AdvancedDropdownItem( "Saturday" ) );
        weekend.AddChild( new AdvancedDropdownItem( "Sunday" ) );

        root.AddChild( firstHalf );
        root.AddChild( secondHalf );
        root.AddChild( weekend );

        return root;
    }

    protected override void ItemSelected( AdvancedDropdownItem item )
    {
        OnSelect?.Invoke( item );
    }
}

public class AdvancedDropdownTestWindow : EditorWindow
{
    [MenuItem( "Tools/Hoge" )]
    private static void Open()
    {
        GetWindow<AdvancedDropdownTestWindow>();
    }

    void OnGUI()
    {
        var rect = GUILayoutUtility.GetRect( new GUIContent( "Show" ), EditorStyles.toolbarButton );
        if ( GUI.Button( rect, new GUIContent( "Show" ), EditorStyles.toolbarButton ) )
        {
            var dropdown = new WeekdaysDropdown( new AdvancedDropdownState() );
            dropdown.OnSelect += item => Debug.Log( item.name );
            dropdown.Show( rect );
        }
    }
}

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