不正确地使用ParentDataWidget

class MyParentData extends ParentDataWidget<MyParentData> {
  // 自定义的ParentDataWidget子类
  MyParentData({Key key, @required Widget child, @required this.myData})
      : super(key: key, child: child);

  final String myData; // 存储布局约束和位置信息的属性

  @override
  void applyParentData(RenderObject renderObject) {
    final BoxParentData parentData = renderObject.parentData as BoxParentData;
    if (parentData != null) {
      // 将myData应用到对应的RenderObject上
      parentData.myData = myData;
    }
  }

  @override
  Type get debugTypicalAncestorWidgetClass => MyParentData; // 调试时显示的Widget类型

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(DiagnosticsProperty<String>('myData', myData)); // 调试时显示的属性值
  }
}

class MyWidget extends SingleChildRenderObjectWidget {
  MyWidget({Key key, Widget child}) : super(key: key, child: child);

  @override
  RenderObject createRenderObject(BuildContext context) {
    return RenderMyWidget();
  }

  @override
  void updateRenderObject(BuildContext context, RenderMyWidget renderObject) {
    // 更新RenderObject
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    // 添加ParentDataWidget子类与对应的RenderObject的关联
    if (child != null) {
      child.debugFillProperties(properties);
    }
  }
}

class RenderMyWidget extends RenderBox {
  String myData; // 与ParentDataWidget子类关联的属性

  @override
  void performLayout() {
    // 执行布局
  }

  @override
  void paint(PaintingContext context, Offset offset) {
    // 绘制
  }
}

void main() {
  runApp(
    MyParentData(
      myData: 'example data',
      child: MyWidget(
        child: Container(),
      ),
    ),
  );
}