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

using System;
using uiwidgets;
using Unity.UIWidgets.animation;
using Unity.UIWidgets.foundation;
using Unity.UIWidgets.ui;
using Unity.UIWidgets.widgets;

namespace UIWidgetsSample.RaycastableScene
{
    public class AnimateButton : StatefulWidget
    {
        public AnimateButton(Key key = null, Widget child = null, bool selected = false) : base(key: key)
        {
            this.child = child;
            this.selected = selected;
        }
        
        public readonly Widget child;
        public readonly bool selected;
        
        public override State createState()
        {
            return new AnimateButtonState();
        }
    }

    public class AnimateButtonState : SingleTickerProviderStateMixin<AnimateButton>
    {
        private AnimationController selectAnim;
        private Animation<Color> _colorTween;

        public override void initState()
        {
            selectAnim = new AnimationController(vsync: this, duration: new TimeSpan(0, 0, 0, 0, 200));
            _colorTween = new ColorTween(begin: Colors.white, Colors.green).animate(selectAnim);
            base.initState();
        }

        public override void dispose()
        {
            base.dispose();
            selectAnim.dispose();
        }


        public override Widget build(BuildContext context)
        {
            if (widget.selected)
            {
                selectAnim.forward();
            }
            else
            {
                selectAnim.reverse();
            }
            
            return new AnimatedBuilder(
                    animation: _colorTween,
                    builder: (build_context, child) =>
                    {
                        return new Container(
                            color: _colorTween.value,
                            child: widget.child);
                    }
                );
        }
    }
}