如何使用Flutter下载文件并将其存储在Downloads文件夹中 [英] How to download a file and store it in Downloads folder using Flutter

问题描述

我正在使用Flutter 1.10.3构建应用程序，并且在将图像下载到设备的下载"文件夹时遇到困难.

I'm building an App using Flutter 1.10.3 and I'm having difficulties downloading images to the Downloads folder of the device.

是否可以选择不使用任何第3部分库?

Is there an option to do so without using any 3rd-part libraries?

推荐答案

添加一些必需的依赖项，我仅使用android进行测试演示.在IOS设备中实施时，请查看file_utils和path_provider.

Add few required dependencies, I have test demo with android only. please review file_utils and path_provider while you implement in IOS device.

  dio: ^3.0.0

  path_provider: ^1.3.0

  simple_permissions: ^0.1.9

  file_utils: ^0.1.3

您需要在Android mainfest文件上添加权限.

You required to add permissons on android mainfest file.

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

示例代码:

  import 'dart:io';
  import 'package:flutter/material.dart';
  import 'package:dio/dio.dart';
  import 'package:path_provider/path_provider.dart';
  import 'dart:async';
  import 'package:simple_permissions/simple_permissions.dart';
  import 'package:file_utils/file_utils.dart';
  import 'dart:math';

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

  class Downloader extends StatelessWidget {
    @override
    Widget build(BuildContext context) => MaterialApp(
          title: "File Downloader",
          debugShowCheckedModeBanner: false,
          home: FileDownloader(),
          theme: ThemeData(primarySwatch: Colors.blue),
        );
  }

  class FileDownloader extends StatefulWidget {
    @override
    _FileDownloaderState createState() => _FileDownloaderState();
  }

  class _FileDownloaderState extends State<FileDownloader> {

    final imgUrl = "https://images6.alphacoders.com/683/thumb-1920-683023.jpg";
    bool downloading = false;
    var progress = "";
    var path = "No Data";
    var platformVersion = "Unknown";
    Permission permission1 = Permission.WriteExternalStorage;
    var _onPressed;
    static final Random random = Random();
    Directory externalDir;

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


    Future<void> downloadFile() async {
      Dio dio = Dio();
      bool checkPermission1 =
          await SimplePermissions.checkPermission(permission1);
      // print(checkPermission1);
      if (checkPermission1 == false) {
        await SimplePermissions.requestPermission(permission1);
        checkPermission1 = await SimplePermissions.checkPermission(permission1);
      }
      if (checkPermission1 == true) {
        String dirloc = "";
        if (Platform.isAndroid) {
          dirloc = "/sdcard/download/";
        } else {
          dirloc = (await getApplicationDocumentsDirectory()).path;
        }

        var randid = random.nextInt(10000);

        try {
          FileUtils.mkdir([dirloc]);
          await dio.download(imgUrl, dirloc + randid.toString() + ".jpg",
              onReceiveProgress: (receivedBytes, totalBytes) {
            setState(() {
              downloading = true;
              progress =
                  ((receivedBytes / totalBytes) * 100).toStringAsFixed(0) + "%";
            });
          });
        } catch (e) {
          print(e);
        }

        setState(() {
          downloading = false;
          progress = "Download Completed.";
          path = dirloc + randid.toString() + ".jpg";
        });
      } else {
        setState(() {
          progress = "Permission Denied!";
          _onPressed = () {
            downloadFile();
          };
        });
      }
    }

    @override
    Widget build(BuildContext context) => Scaffold(
        appBar: AppBar(
          title: Text('File Downloader'),
        ),
        body: Center(
            child: downloading
                ? Container(
                    height: 120.0,
                    width: 200.0,
                    child: Card(
                      color: Colors.black,
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: <Widget>[
                          CircularProgressIndicator(),
                          SizedBox(
                            height: 10.0,
                          ),
                          Text(
                            'Downloading File: $progress',
                            style: TextStyle(color: Colors.white),
                          ),
                        ],
                      ),
                    ),
                  )
                : Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    children: <Widget>[
                      Text(path),
                      MaterialButton(
                        child: Text('Request Permission Again.'),
                        onPressed: _onPressed,
                        disabledColor: Colors.blueGrey,
                        color: Colors.pink,
                        textColor: Colors.white,
                        height: 40.0,
                        minWidth: 100.0,
                      ),
                    ],
                  )));
  }

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