How to make an online radio app in Flutter part 1

home_screen.dart

class HomeScreen extends StatelessWidget {
  final _planetRockUrl = 'https://stream-mz.planetradio.co.uk/planetrock.mp3';
  final _planetRockImage = 'assets/images/planet_rock.png';

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Online Radio'),
      ),
      body: Padding(
        padding: const EdgeInsets.only(bottom: 100),
        child: Container(
          child: Center(
            child: BlocBuilder<PlayerBloc, PlayerState>(builder: (context, state) {
              if (state is PausedState) {
                return IdleDots(color: Theme.of(context).accentColor);
              } else if (state is PlayingState) {
                return Loading(
                  indicator: LineScalePulseOutIndicator(),
                  size: 100,
                  color: Theme.of(context).accentColor,
                );
              } else {
                throw Exception('Unknown state of bloc');
              }
            }),
          ),
        ),
      ),
      bottomSheet: Container(
        color: Theme.of(context).primaryColor,
        height: 100,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceBetween,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.all(16.0),
              child: Container(
                height: 50,
                width: 50,
                child: Image.asset(_planetRockImage),
              ),
            ),
            Text(
              'Planet Rock',
              style: TextStyle(fontWeight: FontWeight.bold),
            ),
            Padding(
              padding: const EdgeInsets.all(16.0),
              child: BlocBuilder<PlayerBloc, PlayerState>(
                bloc: BlocProvider.of<PlayerBloc>(context),
                builder: (context, state) {
                  if (state is PausedState) {
                    return IconButton(
                      icon: Icon(
                        Icons.play_arrow,
                        size: 32,
                      ),
                      onPressed: () {
                        context.bloc<PlayerBloc>().add(PlayEvent(url: _planetRockUrl));
                      },
                    );
                  } else {
                    return IconButton(
                      icon: Icon(
                        Icons.pause,
                        size: 32,
                      ),
                      onPressed: () {
                        context.bloc<PlayerBloc>().add(PauseEvent());
                      },
                    );
                  }
                },
              ),
            )
          ],
        ),
      ),
    );
  }
}

main.dart

class RadioApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final RadioPlayer radioPlayer = JustAudioPlayer();
    return MaterialApp(
      title: 'Online Radio',
      debugShowCheckedModeBanner: false,
      theme: ThemeData.dark(),
      home: BlocProvider<PlayerBloc>(
        create: (context) => PlayerBloc(radioPlayer: radioPlayer),
        child: HomeScreen(),
      ),
    );
  }
}

media_button.dart

  BlocBuilder<PlayerBloc, PlayerState>(
      bloc: BlocProvider.of<PlayerBloc>(context),
      builder: (context, state) {
        if (state is PausedState) {
          return IconButton(
            icon: Icon(
              Icons.play_arrow,
              size: 32,
            ),
            onPressed: () {
              context.bloc<PlayerBloc>().add(PlayEvent(url: _planetRockUrl));
            },
          );
        } else {
          return IconButton(
            icon: Icon(
              Icons.pause,
              size: 32,
            ),
            onPressed: () {
              context.bloc<PlayerBloc>().add(PauseEvent());
            },
          );
        }
      },
    );

player_bloc.dart

class PlayerBloc extends Bloc<PlayerEvent, PlayerState> {
  final RadioPlayer radioPlayer;

  PlayerBloc({@required this.radioPlayer}) : assert(radioPlayer != null);

  @override
  PlayerState get initialState => PausedState();

  @override
  Stream<PlayerState> mapEventToState(
    PlayerEvent event,
  ) async* {
    if (event is PlayEvent && state is! PlayingState) {
      radioPlayer.play(url: event.url);
      yield PlayingState();
    } else if (event is PauseEvent) {
      radioPlayer.pause();
      yield PausedState();
    }
  }
}

pubspec.yaml

dependencies:
  flutter:
    sdk: flutter
  bloc: ^3.0.0
  flutter_bloc: ^3.2.0
  just_audio: ^0.1.3
  loading: ^1.0.2
  
flutter:
  uses-material-design: true
  assets:
    - assets/images/

radio_player.dart

abstract class RadioPlayer {
  Future<void> play({@required String url});
  Future<void> pause();
}

class JustAudioPlayer extends RadioPlayer {
  final audioPlayer = AudioPlayer();
  var _isUrlSet = false;

  @override
  Future<void> pause() {
    return audioPlayer.pause();
  }

  @override
  Future<void> play({@required String url}) async {
    if (!_isUrlSet) {
      await audioPlayer.setUrl(url);
      _isUrlSet = true;
    }
    return audioPlayer.play();
  }
}

status_widget.dart

    BlocBuilder<PlayerBloc, PlayerState>(
      builder: (context, state) {
        if (state is PausedState) {
          return IdleDots(color: Theme.of(context).accentColor);
        } else if (state is PlayingState) {
          return Loading(
            indicator: LineScalePulseOutIndicator(),
            size: 100,
            color: Theme.of(context).accentColor,
          );
        } else {
          throw Exception('Unknown state of bloc');
        }
      },
    );