如何截取当前Widget的屏幕截图？

import 'dart:ui' as ui;
import 'package:flutter/rendering.dart';
import 'package:image_gallery_saver/image_gallery_saver.dart';

GlobalKey globalKey = GlobalKey();
...
Widget(
  key: globalKey,
  ...
)

Future<ui.Image> captureScreen() async {
  RenderRepaintBoundary boundary = globalKey.currentContext.findRenderObject();
  ui.Image image = await boundary.toImage();
  return image;
}

ui.Image image = await captureScreen();
ByteData byteData = await image.toByteData(format: ui.ImageByteFormat.png);
Uint8List pngBytes = byteData.buffer.asUint8List();

final result = await ImageGallerySaver.saveImage(pngBytes);
if (result['isSuccess']) {
  print('截图保存成功');
} else {
  print('截图保存失败');
}