如何为AnimatedContainer创建setState函数

class MyAnimatedContainer extends StatefulWidget {
  @override
  _MyAnimatedContainerState createState() => _MyAnimatedContainerState();
}

class _MyAnimatedContainerState extends State<MyAnimatedContainer> {
  // 在这里定义AnimatedContainer的属性
  double _width = 100.0;
  double _height = 100.0;
  Color _color = Colors.blue;

  @override
  Widget build(BuildContext context) {
    return AnimatedContainer(
      width: _width,
      height: _height,
      color: _color,
      duration: Duration(seconds: 1),
      curve: Curves.easeInOut,
    );
  }
}

void _setContainerSize() {
  setState(() {
    _width = 200.0;
    _height = 200.0;
  });
}

@override
Widget build(BuildContext context) {
  return Column(
    children: [
      AnimatedContainer(
        width: _width,
        height: _height,
        color: _color,
        duration: Duration(seconds: 1),
        curve: Curves.easeInOut,
      ),
      RaisedButton(
        onPressed: _setContainerSize,
        child: Text('改变尺寸'),
      ),
    ],
  );
}