awesome-uiwidgets/AwesomeUIWidgets/Assets/Scripts/RaycastableScene/ItemPickerMainUIPanel.cs

using System.Collections.Generic;
using uiwidgets;
using Unity.UIWidgets.engine;
using Unity.UIWidgets.material;
using Unity.UIWidgets.widgets;
using UnityEngine;

namespace UIWidgetsSample.RaycastableScene
{
    public class ItemPickerMainUIPanel : UIWidgetsRaycastablePanel
    {
        protected override void main()
        {
            ui_.runApp(new ItemPickerMainUI());
        }
    }

    public class ItemPickerMainUI : StatelessWidget
    {
        public override Widget build(BuildContext context)
        {
            return new MaterialApp(
                home: new Scaffold(
                    backgroundColor: Colors.blue.withAlpha(64),
                    body: new ItemPickerMainWidget()
                    )
                );
        }
    }

    public class ItemPickerMainWidget : StatefulWidget
    {
        public override State createState()
        {
            return new ItemPickerMainWidgetState();
        }
    }

    public class ItemPickerMainWidgetState : State<ItemPickerMainWidget>
    {
        public override Widget build(BuildContext context)
        {
            return new Column(
                    children: new List<Widget>
                    {
                        buildTop(),
                        buildMiddle()
                    }
                );
        }

        private Widget buildTop()
        {
            return new RaycastableContainer(child: new Container(height: 50f, color: Colors.blue));
        }

        private Widget buildMiddle()
        {
            return new Expanded(child: new Row(
                    children: new List<Widget>
                    {
                        buildLeft(),
                        new Container()
                    }
                ));
        }

        private Widget buildLeft()
        {
            return new RaycastableContainer(child: new Container(width: 100f, color: Colors.green));
        }
    }
}