Flutter Dio 下载文件并显示下载进度

import 'dart:io';
import 'package:dio/dio.dart';

class DownloadPage extends StatefulWidget {
  @override
  _DownloadPageState createState() => _DownloadPageState();
}

class _DownloadPageState extends State<DownloadPage> {
  double _progress = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("下载文件")),
      body: Column(
        children: [
          RaisedButton(
            onPressed: () async {
              final url = "https://example.com/file.zip";
              final filename = "file.zip";
              await downloadFile(url, filename);
            },
            child: Text("下载"),
          ),
          Container(
            width: double.infinity,
            child: LinearProgressIndicator(value: _progress),
          ),
        ],
      ),
    );
  }

  Future<void> downloadFile(String url, String filename) async {
    Dio dio = Dio();

    try {
      Response response = await dio.download(url, filename,
          onReceiveProgress: (received, total) {
        setState(() {
          if (total != -1) {
            _progress = received / total;
          }
        });
      });
      print(response.data);
    } catch (e) {
      print(e);
    }
  }
}