使用flutter web从URL下载文件

import 'package:flutter_web/material.dart';
import 'package:http/http.dart' as http;
import 'dart:io';

class DownloadFilePage extends StatefulWidget {
  @override
  _DownloadFilePageState createState() => _DownloadFilePageState();
}

class _DownloadFilePageState extends State<DownloadFilePage> {
  String _progressMessage = '';
  String _filePath = '';

  Future<void> _downloadFile() async {
    String url = 'https://example.com/file.txt'; // 文件的URL地址
    String savePath = '/path/to/save/file.txt'; // 文件保存的路径

    http.Response response = await http.get(url);
    if (response.statusCode == 200) {
      File file = File(savePath);
      await file.writeAsBytes(response.bodyBytes);
      setState(() {
        _progressMessage = '文件下载完成';
        _filePath = savePath;
      });
    } else {
      setState(() {
        _progressMessage = '文件下载失败';
        _filePath = '';
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('下载文件示例'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
              child: Text('下载文件'),
              onPressed: _downloadFile,
            ),
            Text(_progressMessage),
            Text(_filePath),
          ],
        ),
      ),
    );
  }
}

dependencies:
  flutter:
    sdk: flutter
  flutter_web:
    sdk: flutter_web
  http: any

web:
  build:
    options:
      --dart-define=FLUTTER_WEB_AUTO_DETECT=false
  compiler:
    web:
      dart-define: FLUTTER_WEB_AUTO_DETECT=false

import 'dart:html';