如何获取可组合组件的MeasuredWitdh和MeasuredHeight？

final GlobalKey _key = GlobalKey();

MyComponent(
  key: _key,
  // ... 其他属性
)

void getDimensions() {
  final RenderBox renderBox = _key.currentContext?.findRenderObject() as RenderBox;
  if (renderBox != null) {
    print('Measured Width: ${renderBox.measuredWidth}');
    print('Measured Height: ${renderBox.measuredHeight}');
  }
}

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text('Measure Widget Size')),
        body: Center(
          child: MeasureWidget(key: GlobalKey()),
        ),
      ),
    );
  }
}

class MeasureWidget extends StatefulWidget {
  final GlobalKey key;

  MeasureWidget({required this.key});

  @override
  _MeasureWidgetState createState() => _MeasureWidgetState();
}

class _MeasureWidgetState extends State<MeasureWidget> {
  GlobalKey _key = GlobalKey();

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) {
      getDimensions();
    });
  }

  void getDimensions() {
    final RenderBox renderBox = _key.currentContext?.findRenderObject() as RenderBox;
    if (renderBox != null) {
      print('Measured Width: ${renderBox.measuredWidth}');
      print('Measured Height: ${renderBox.measuredHeight}');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      key: _key,
      color: Colors.blue,
      width: 200,
      height: 100,
    );
  }
}