如何使用颤振 dio 下载文件？答案

【问题标题】：How can I download file using flutter dio?如何使用颤振 dio 下载文件？
【发布时间】：2020-04-24 06:18:39
【问题描述】：

我想在 Flutter Dio 的帮助下使用 url 下载文件。

  final imgUrl = "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf";
  var dio = Dio();

RaisedButton.icon(
                  onPressed: (){
                    download2(dio, imgUrl, "./example/boo2.pdf");
                  },
                  icon: Icon(Icons.file_download,color: Colors.white,),
                  color: Colors.green,
                  textColor: Colors.white,
                  label: Text('Dowload Invoice')
              )

 Future download2(Dio dio, String url, String savePath) async {
    try {
      Response response = await dio.get(
        url,
        onReceiveProgress: showDownloadProgress,
        //Received data with List<int>
        options: Options(
            responseType: ResponseType.bytes,
            followRedirects: false,
            validateStatus: (status) { return status < 500; }
            ),
      );
      print(response.headers);
      File file = File(savePath);
      var raf = file.openSync(mode: FileMode.write);
      // response.data is List<int> type
      raf.writeFromSync(response.data);
      await raf.close();
    } catch (e) {
      print(e);
    }
  }

  void showDownloadProgress(received, total) {
    if (total != -1) {
      print((received / total * 100).toStringAsFixed(0) + "%");
    }
  }

我遇到了这个错误。

操作系统错误：权限被拒绝，errno = 13flutter

【问题讨论】：

标签： android ios http flutter dart

【解决方案1】：

您可以在下面复制粘贴运行完整代码
您需要使用https://pub.dev/packages/path_provider 获取临时目录

代码sn-p

RaisedButton.icon(
                onPressed: () async {
                  var tempDir = await getTemporaryDirectory();
                  String fullPath = tempDir.path + "/boo2.pdf'";
                  print('full path ${fullPath}');

                  download2(dio, imgUrl, fullPath);
                },
                icon: Icon(
                  Icons.file_download,
                  color: Colors.white,
                ),
                color: Colors.green,
                textColor: Colors.white,
                label: Text('Dowload Invoice'))

工作演示

完整代码

import 'package:flutter/material.dart';
import 'package:dio/dio.dart';
import 'package:path_provider/path_provider.dart';
import 'dart:io';

final imgUrl =
    "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf";
var dio = Dio();

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  Future download2(Dio dio, String url, String savePath) async {
    try {
      Response response = await dio.get(
        url,
        onReceiveProgress: showDownloadProgress,
        //Received data with List<int>
        options: Options(
            responseType: ResponseType.bytes,
            followRedirects: false,
            validateStatus: (status) {
              return status < 500;
            }),
      );
      print(response.headers);
      File file = File(savePath);
      var raf = file.openSync(mode: FileMode.write);
      // response.data is List<int> type
      raf.writeFromSync(response.data);
      await raf.close();
    } catch (e) {
      print(e);
    }
  }

  void showDownloadProgress(received, total) {
    if (total != -1) {
      print((received / total * 100).toStringAsFixed(0) + "%");
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton.icon(
                onPressed: () async {
                  var tempDir = await getTemporaryDirectory();
                  String fullPath = tempDir.path + "/boo2.pdf'";
                  print('full path ${fullPath}');

                  download2(dio, imgUrl, fullPath);
                },
                icon: Icon(
                  Icons.file_download,
                  color: Colors.white,
                ),
                color: Colors.green,
                textColor: Colors.white,
                label: Text('Dowload Invoice')),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

【讨论】：

如果我想将此文件存储在我的下载文件夹中，我该如何提供路径？
表示我要存储下载文件的任何特定位置。
你不能做任何文件夹，Android较新版本中的大部分文件夹都受到保护。您可以在 getTemporaryDirectory() 中创建一个文件夹
但是下载的文件没有显示在我的手机中。
如果您不授予写入外部存储的权限，则会发生错误

【解决方案2】：

您必须添加权限。

对于 Android：在 AndroidManifest.xml 中

  <manifest...
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.INTERNET"/>

pubspec.yaml

ext_storage: ^1.0.3

你的.dart

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

  //get storage permission
  void getPermission() async {
    await PermissionHandler().requestPermissions([PermissionGroup.storage]);
  }

【讨论】：