get rect from rendered widget

main.dart

Rect getRectFromWidget(GlobalKey gKey) {
    final keyContext = gKey.currentContext;
    if (keyContext != null) {
      final box = keyContext.findRenderObject() as RenderBox;
      final offset = box.localToGlobal(Offset.zero);
      final size = box.hasSize ? box.size : Size.zero;
      return Rect.fromLTWH(offset.dx, offset.dy, size.width, size.height);
    }
    return Rect.zero;
}