just_audio/example/lib/main.dart

import 'dart:math';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:just_audio/just_audio.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  AudioPlayer _player;
  ConcatenatingAudioSource _playlist = ConcatenatingAudioSource(children: [
    LoopingAudioSource(
      count: 2,
      child: ClippingAudioSource(
        start: Duration(seconds: 60),
        end: Duration(seconds: 65),
        child: AudioSource.uri(Uri.parse(
            "https://s3.amazonaws.com/scifri-episodes/scifri20181123-episode.mp3")),
        tag: AudioMetadata(
          album: "Science Friday",
          title: "A Salute To Head-Scratching Science (5 seconds)",
          artwork:
              "https://media.wnyc.org/i/1400/1400/l/80/1/ScienceFriday_WNYCStudios_1400.jpg",
        ),
      ),
    ),
    AudioSource.uri(
      Uri.parse(
          "https://s3.amazonaws.com/scifri-episodes/scifri20181123-episode.mp3"),
      tag: AudioMetadata(
        album: "Science Friday",
        title: "A Salute To Head-Scratching Science",
        artwork:
            "https://media.wnyc.org/i/1400/1400/l/80/1/ScienceFriday_WNYCStudios_1400.jpg",
      ),
    ),
    AudioSource.uri(
      Uri.parse("https://s3.amazonaws.com/scifri-segments/scifri201711241.mp3"),
      tag: AudioMetadata(
        album: "Science Friday",
        title: "From Cat Rheology To Operatic Incompetence",
        artwork:
            "https://media.wnyc.org/i/1400/1400/l/80/1/ScienceFriday_WNYCStudios_1400.jpg",
      ),
    ),
  ]);

  List<IndexedAudioSource> get _sequence => _playlist.sequence;

  List<AudioMetadata> get _metadataSequence =>
      _sequence.map((s) => s.tag as AudioMetadata).toList();

  @override
  void initState() {
    super.initState();
    AudioPlayer.setIosCategory(IosCategory.playback);
    _player = AudioPlayer();
    SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle(
      statusBarColor: Colors.black,
    ));
    _loadAudio();
  }

  _loadAudio() async {
    try {
      await _player.load(_playlist);
    } catch (e) {
      // catch load errors: 404, invalid url ...
      print("An error occured (${e.code}): ${e.message}");
    }
  }

  @override
  void dispose() {
    _player.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: SafeArea(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Expanded(
                child: StreamBuilder<int>(
                  stream: _player.currentIndexStream,
                  builder: (context, snapshot) {
                    final index = snapshot.data ?? 0;
                    final metadata = _metadataSequence[index];
                    return Column(
                      crossAxisAlignment: CrossAxisAlignment.center,
                      children: [
                        Expanded(
                          child: Padding(
                            padding: const EdgeInsets.all(8.0),
                            child:
                                Center(child: Image.network(metadata.artwork)),
                          ),
                        ),
                        Text(metadata.album ?? '',
                            style: Theme.of(context).textTheme.headline6),
                        Text(metadata.title ?? ''),
                      ],
                    );
                  },
                ),
              ),
              StreamBuilder<PlayerState>(
                stream: _player.playerStateStream,
                builder: (context, snapshot) {
                  final playerState = snapshot.data;
                  final processingState = playerState?.processingState;
                  final playing = playerState?.playing;
                  return Row(
                    mainAxisSize: MainAxisSize.min,
                    children: [
                      IconButton(
                        icon: Icon(Icons.volume_up),
                        onPressed: () {
                          _showSliderDialog(
                            context: context,
                            title: "Adjust volume",
                            divisions: 10,
                            min: 0.0,
                            max: 1.0,
                            stream: _player.volumeStream,
                            onChanged: _player.setVolume,
                          );
                        },
                      ),
                      IconButton(
                        icon: Icon(Icons.skip_previous),
                        onPressed:
                            _player.hasPrevious ? _player.seekToPrevious : null,
                      ),
                      if (processingState == ProcessingState.loading ||
                          processingState == ProcessingState.buffering)
                        Container(
                          margin: EdgeInsets.all(8.0),
                          width: 64.0,
                          height: 64.0,
                          child: CircularProgressIndicator(),
                        )
                      else if (playing != true)
                        IconButton(
                          icon: Icon(Icons.play_arrow),
                          iconSize: 64.0,
                          onPressed: _player.play,
                        )
                      else if (processingState != ProcessingState.completed)
                        IconButton(
                          icon: Icon(Icons.pause),
                          iconSize: 64.0,
                          onPressed: _player.pause,
                        )
                      else
                        IconButton(
                          icon: Icon(Icons.replay),
                          iconSize: 64.0,
                          onPressed: () =>
                              _player.seek(Duration.zero, index: 0),
                        ),
                      IconButton(
                        icon: Icon(Icons.skip_next),
                        onPressed: _player.hasNext ? _player.seekToNext : null,
                      ),
                      IconButton(
                        icon: StreamBuilder<double>(
                            stream: _player.speedStream,
                            builder: (context, snapshot) => Text(
                                "${snapshot.data?.toStringAsFixed(1)}x",
                                style: TextStyle(fontWeight: FontWeight.bold))),
                        onPressed: () {
                          _showSliderDialog(
                            context: context,
                            title: "Adjust speed",
                            divisions: 10,
                            min: 0.5,
                            max: 1.5,
                            stream: _player.speedStream,
                            onChanged: _player.setSpeed,
                          );
                        },
                      ),
                    ],
                  );
                },
              ),
              StreamBuilder<Duration>(
                stream: _player.durationStream,
                builder: (context, snapshot) {
                  final duration = snapshot.data ?? Duration.zero;
                  return StreamBuilder<Duration>(
                    stream: _player.positionStream,
                    builder: (context, snapshot) {
                      var position = snapshot.data ?? Duration.zero;
                      if (position > duration) {
                        position = duration;
                      }
                      return SeekBar(
                        duration: duration,
                        position: position,
                        onChangeEnd: (newPosition) {
                          _player.seek(newPosition);
                        },
                      );
                    },
                  );
                },
              ),
              SizedBox(height: 8.0),
              Row(
                children: [
                  StreamBuilder<LoopMode>(
                    stream: _player.loopModeStream,
                    builder: (context, snapshot) {
                      final loopMode = snapshot.data ?? LoopMode.off;
                      const icons = [
                        Icon(Icons.repeat, color: Colors.grey),
                        Icon(Icons.repeat, color: Colors.orange),
                        Icon(Icons.repeat_one, color: Colors.orange),
                      ];
                      const cycleModes = [
                        LoopMode.off,
                        LoopMode.all,
                        LoopMode.one,
                      ];
                      final index = cycleModes.indexOf(loopMode);
                      return IconButton(
                        icon: icons[index],
                        onPressed: () {
                          _player.setLoopMode(cycleModes[
                              (cycleModes.indexOf(loopMode) + 1) %
                                  cycleModes.length]);
                        },
                      );
                    },
                  ),
                  Expanded(
                    child: Text(
                      "Playlist",
                      style: Theme.of(context).textTheme.headline6,
                      textAlign: TextAlign.center,
                    ),
                  ),
                  StreamBuilder<bool>(
                    stream: _player.shuffleModeEnabledStream,
                    builder: (context, snapshot) {
                      final shuffleModeEnabled = snapshot.data ?? false;
                      return IconButton(
                        icon: shuffleModeEnabled
                            ? Icon(Icons.shuffle, color: Colors.orange)
                            : Icon(Icons.shuffle, color: Colors.grey),
                        onPressed: () {
                          _player.setShuffleModeEnabled(!shuffleModeEnabled);
                        },
                      );
                    },
                  ),
                ],
              ),
              Container(
                height: 240.0,
                child: StreamBuilder<int>(
                  stream: _player.currentIndexStream,
                  builder: (context, snapshot) {
                    final currentIndex = snapshot.data ?? 0;
                    return ListView.builder(
                      itemCount: _metadataSequence.length,
                      itemBuilder: (context, index) => Material(
                        color:
                            index == currentIndex ? Colors.grey.shade300 : null,
                        child: ListTile(
                          title: Text(_metadataSequence[index].title),
                          onTap: () {
                            _player.seek(Duration.zero, index: index);
                          },
                        ),
                      ),
                    );
                  },
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class SeekBar extends StatefulWidget {
  final Duration duration;
  final Duration position;
  final ValueChanged<Duration> onChanged;
  final ValueChanged<Duration> onChangeEnd;

  SeekBar({
    @required this.duration,
    @required this.position,
    this.onChanged,
    this.onChangeEnd,
  });

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

class _SeekBarState extends State<SeekBar> {
  double _dragValue;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        Slider(
          min: 0.0,
          max: widget.duration.inMilliseconds.toDouble(),
          value: min(_dragValue ?? widget.position.inMilliseconds.toDouble(),
              widget.duration.inMilliseconds.toDouble()),
          onChanged: (value) {
            setState(() {
              _dragValue = value;
            });
            if (widget.onChanged != null) {
              widget.onChanged(Duration(milliseconds: value.round()));
            }
          },
          onChangeEnd: (value) {
            if (widget.onChangeEnd != null) {
              widget.onChangeEnd(Duration(milliseconds: value.round()));
            }
            _dragValue = null;
          },
        ),
        Positioned(
          right: 16.0,
          bottom: 0.0,
          child: Text(
              RegExp(r'((^0*[1-9]\d*:)?\d{2}:\d{2})\.\d+$')
                      .firstMatch("$_remaining")
                      ?.group(1) ??
                  '$_remaining',
              style: Theme.of(context).textTheme.caption),
        ),
      ],
    );
  }

  Duration get _remaining => widget.duration - widget.position;
}

_showSliderDialog({
  BuildContext context,
  String title,
  int divisions,
  double min,
  double max,
  String valueSuffix = '',
  Stream<double> stream,
  ValueChanged<double> onChanged,
}) {
  showDialog(
    context: context,
    builder: (context) => AlertDialog(
      title: Text(title, textAlign: TextAlign.center),
      content: StreamBuilder<double>(
        stream: stream,
        builder: (context, snapshot) => Container(
          height: 100.0,
          child: Column(
            children: [
              Text('${snapshot.data?.toStringAsFixed(1)}$valueSuffix',
                  style: TextStyle(
                      fontFamily: 'Fixed',
                      fontWeight: FontWeight.bold,
                      fontSize: 24.0)),
              Slider(
                divisions: divisions,
                min: min,
                max: max,
                value: snapshot.data ?? 1.0,
                onChanged: onChanged,
              ),
            ],
          ),
        ),
      ),
    ),
  );
}

class AudioMetadata {
  final String album;
  final String title;
  final String artwork;

  AudioMetadata({this.album, this.title, this.artwork});
}