How to download a file and store it in Downloads folder using Flutter

Question

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

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

Answer 1

Add few required dependencies, I have a 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

Note: simple_permissions is disconnected please use this dependency permission_handler

You are required to add permissions on the android manifest 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" />

Sample code:

  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,
                      ),
                    ],
                  )));
  }