[Memo] Dart x Flutter: Get widget offset and size in real time

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

  double lastDx = 0.0;
  double lastDy = 0.0;
  double lastDw = 0.0;
  double lastDh = 0.0;

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

class MyContainerRenderObject extends RenderProxyBox {
  MyContainer myparent;

  MyContainerRenderObject(this.myparent) {

  }

  @override
  void paint(PaintingContext context, Offset offset) {
    assert(!debugNeedsLayout);
    this.myparent.lastDx = offset.dx;
    this.myparent.lastDy = offset.dy;
    this.myparent.lastDw = size.width;
    this.myparent.lastDh = size.height;
    print("size: ${this.size}");
    print("offset ${offset.dx} ${offset.dy}");
    super.paint(context, offset);
  }
}