Flutter Bloc Dio Download Example

download_bloc.dart

import 'dart:async';

import 'package:bloc/bloc.dart';
import 'package:equatable/equatable.dart';
import 'package:flutter_download/download_service.dart';
import 'package:meta/meta.dart';

part 'download_event.dart';
part 'download_state.dart';

class DownloadBloc extends Bloc<DownloadEvent, DownloadState> {
  final DownloadService downloadService;

  DownloadBloc({@required this.downloadService})
      : assert(downloadService != null);

  @override
  DownloadState get initialState => DownloadInitial();

  @override
  Stream<DownloadState> mapEventToState(DownloadEvent event) async* {
    if (event is DownloadStarted) {
      yield DownloadLoadInProgress();
      downloadService.downloadFile(
        progressCallback: (count, total) {
          add(DownloadStatusChanged((count * 100 ~/ total)));
        },
      ).catchError((_) => add(DownloadErrored()));
    } else if (event is DownloadStatusChanged) {
      yield event.progress == 100
          ? DownloadSuccess()
          : DownloadLoadInProgress(progress: event.progress);
    } else if (event is DownloadErrored) {
      yield DownloadFailure();
    }
  }
}

download_event.dart

part of 'download_bloc.dart';

@immutable
abstract class DownloadEvent extends Equatable {
  @override
  List<Object> get props => [];
}

class DownloadStarted extends DownloadEvent {}

class DownloadStatusChanged extends DownloadEvent {
  final int progress;

  DownloadStatusChanged(this.progress);

  @override
  List<Object> get props => [progress];
}

class DownloadErrored extends DownloadEvent {}

download_service.dart

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

class DownloadService {
  final Dio _dio;

  DownloadService({Dio dio}) : _dio = dio ?? Dio();

  Future<void> downloadFile({ProgressCallback progressCallback}) async {
    final url =
        'http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/ElephantsDream.mp4';
    final downloadDir = await getApplicationDocumentsDirectory();
    final saveFilePath = '${downloadDir.path}/temp.mp4';
    await _dio.download(url, saveFilePath, onReceiveProgress: progressCallback);
  }
}

download_state.dart

part of 'download_bloc.dart';

abstract class DownloadState extends Equatable {
  @override
  List<Object> get props => [];
}

class DownloadInitial extends DownloadState {}

class DownloadLoadInProgress extends DownloadState {
  final int progress;

  DownloadLoadInProgress({this.progress = 0});

  @override
  List<Object> get props => [progress];
}

class DownloadSuccess extends DownloadState {}

class DownloadFailure extends DownloadState {}

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_download/bloc/download_bloc.dart';
import 'package:flutter_download/download_service.dart';
import 'package:flutter_bloc/flutter_bloc.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: MyHomePage());
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {
  final DownloadBloc _downloadBloc = DownloadBloc(
    downloadService: DownloadService(),
  );

  @override
  void dispose() {
    _downloadBloc.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Flutter Bloc Download Example')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            BlocBuilder(
              bloc: _downloadBloc,
              builder: (_, state) {
                if (state is DownloadInitial) {
                  return Text('Please touch on Download FAB');
                }
                if (state is DownloadLoadInProgress) {
                  return Text('Downloading ${state.progress}%');
                }
                if (state is DownloadSuccess) {
                  return Text('Success!');
                }
                return Text('Failure');
              },
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _downloadBloc.add(DownloadStarted()),
        tooltip: 'Download',
        child: const Icon(Icons.file_download),
      ),
    );
  }
}

pubspec.yaml

name: flutter_download
description: A new Flutter application to demonstrate how to yield from callback using flutter_bloc

version: 1.0.0+1

environment:
  sdk: ">=2.7.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  dio: ^3.0.9
  bloc: ^4.0.0
  flutter_bloc: ^4.0.0
  meta: ^1.1.8
  equatable: ^1.1.1
  path_provider: ^1.6.11

flutter:
  uses-material-design: true