flutter 版本自从2.0版本以后很多库都被迫升级。 就连我之前写的将组件生成图片保存到相册（点击这里查看1.0老版本）的功能也需要升级咯，今天刚好有空就重新写了一份，需要的朋友自取，转载需要附上出处哈，谢谢配合

1、引入依赖：

permission_handler: ^7.0.0
image_gallery_saver: '^1.6.9' # 文件保存插件
fluttertoast: ^8.0.7
 path_provider: ^2.0.2

2、引入文件

import 'dart:async';
import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:image_gallery_saver/image_gallery_saver.dart';
import 'package:permission_handler/permission_handler.dart';

3、完整实例代码，可以直接运行

import 'dart:async';
import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'package:image_gallery_saver/image_gallery_saver.dart';
import 'package:permission_handler/permission_handler.dart';

class CapturePage extends StatefulWidget {
  const CapturePage({Key? key}) : super(key: key);

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

class _CapturePageState extends State<CapturePage> {
  GlobalKey _globalKey = GlobalKey();
  List<Uint8List> images = List.empty(growable: true);
  /// 保存图片

  @override
  void initState() {
    super.initState();
    _requestPermission();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Save image to gallery"),
        ),
        body: Center(
          child: Column(
            children: <Widget>[
              RepaintBoundary(
                key: _globalKey,
                child: Container(
                  width: MediaQuery.of(context).size.width*0.6,
                  height: MediaQuery.of(context).size.width*0.6,
                  alignment: Alignment.center,
                  color: Colors.red,
                  child: Text(
                    "RepaintBoundary组件包裹的可以直接生成图片哦",
                    style: TextStyle(
                      color: Colors.white,
                      fontSize: 18
                    ),
                  ),
                ),
              ),
              Container(
                padding: EdgeInsets.only(top: 15),
                child: RaisedButton(
                  onPressed: _saveScreen,
                  child: Text("Save Local Image"),
                ),
                width: 200,
                height: 44,
              ),
            ],
          ),
        ));
  }

  _requestPermission() async {
    Map<Permission, PermissionStatus> statuses = await [
      Permission.storage,
    ].request();

    final info = statuses[Permission.storage].toString();
    print(info);
    _toastInfo(info);
  }

  _saveScreen() async {
    RenderRepaintBoundary boundary =
    _globalKey.currentContext!.findRenderObject() as RenderRepaintBoundary;
    ui.Image image = await boundary.toImage();
    ByteData? byteData = await (image.toByteData(format: ui.ImageByteFormat.png) as FutureOr<ByteData?>);
    if (byteData != null) {
      final result =
      await ImageGallerySaver.saveImage(byteData.buffer.asUint8List());
      print(result);
      _toastInfo(result.toString());
    }
  }

  _toastInfo(String info) {
    Fluttertoast.showToast(msg: info, toastLength: Toast.LENGTH_LONG);
  }

}