关键在利用RepaintBoundary给Widget转为Image。

效果图

import 'dart:typed_data';
import 'dart:ui';

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class NewsPage1 extends StatefulWidget {
  @override
  NewsPage1State createState() => NewsPage1State();
}

class NewsPage1State extends State<NewsPage1> {
  // 全局key
  final GlobalKey _rootWidgetKey = GlobalKey();
  // 图片数组
  List<Uint8List> _images = [];

  /// 截图
  Future<Uint8List?> _capturePng(
      GlobalKey globalKey, {
        double pixelRatio = 1.0, //截屏的图片与原图的比例
      }) async {
    try {
      RenderRepaintBoundary boundary = globalKey.currentContext?.findRenderObject() as RenderRepaintBoundary;
      var image = await boundary.toImage(pixelRatio: pixelRatio);
      ByteData? byteData = await image.toByteData(format: ImageByteFormat.png);
      Uint8List? pngBytes = byteData?.buffer.asUint8List();
      return pngBytes;
    } catch (e) {
      print(e);
    }
    return null;
  }

  @override
  Widget build(BuildContext context) {
    //RepaintBoundary 截屏组件
    return RepaintBoundary(
      key: _rootWidgetKey,
      child: Scaffold(
        appBar: AppBar(
          title: Text("flutter组件截图"),
        ),
        body: Column(
          children: <Widget>[
            TextButton(
              onPressed: () {
                //获取截屏图像
                //添加到图片数组中
                _capturePng(_rootWidgetKey).then((value) {
                  if (value != null) {
                    _images.add(value);
                    setState(() {});
                  }
                });
              },
              child: Text("全屏截图"),
            ),
            Expanded(
              child: ListView.builder(
                itemBuilder: (context, index) {
                  return Image.memory(
                    _images[index],
                    fit: BoxFit.cover,
                  );
                },
                itemCount: _images.length,
                scrollDirection: Axis.horizontal,
              ),
            )
          ],
        ),
      ),
    );
  }
}