设置开始时间后，音频播放器会使模拟器崩溃

Question

我正在构建一个简单的应用，该应用使用audioplayers包播放来自URL的音频。当_play()函数触发时，iOS Simulator崩溃，提示：

iOS => call play, playerId 85966f40-ea00-41b1-bb84-15cd8b8d4ca3
Lost connection to device.
play!
isLocal: 0 0
volume: 1.000000 1

仅当我尝试设置开始时间时才会发生这种情况：

final result = await _audioPlayer.play(url,
        isLocal: isLocal, position: Duration(seconds: 2));

在Android模拟器上也会发生同样的情况，但是当我在iOS设备上运行它时，它可以工作。

我的代码几乎与audioplayers回购中的原始代码相同，如果我更改了原始回购代码中的position值也可以正常工作。可能是什么问题？

这是我的完整代码：

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
          child: PlayerWidget(
              url: 'http://techslides.com/demos/samples/sample.mp3')),
    );
  }
}

enum PlayerState { stopped, playing, paused }

class PlayerWidget extends StatefulWidget {
  final String url;
  final bool isLocal;
  final PlayerMode mode;

  PlayerWidget(
      {@required this.url,
      this.isLocal = false,
      this.mode = PlayerMode.MEDIA_PLAYER});

  @override
  State<StatefulWidget> createState() {
    return new _PlayerWidgetState(url, isLocal, mode);
  }
}

class _PlayerWidgetState extends State<PlayerWidget> {
  String url;
  bool isLocal;
  PlayerMode mode;

  AudioPlayer _audioPlayer;
  AudioPlayerState _audioPlayerState;
  Duration _duration;
  Duration _position;

  PlayerState _playerState = PlayerState.stopped;
  StreamSubscription _durationSubscription;
  StreamSubscription _positionSubscription;
  StreamSubscription _playerCompleteSubscription;
  StreamSubscription _playerErrorSubscription;
  StreamSubscription _playerStateSubscription;

  get _isPlaying => _playerState == PlayerState.playing;
  get _isPaused => _playerState == PlayerState.paused;
  get _durationText => _duration?.toString()?.split('.')?.first ?? '';
  get _positionText => _position?.toString()?.split('.')?.first ?? '';

  _PlayerWidgetState(this.url, this.isLocal, this.mode);

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

  @override
  void dispose() {
    _audioPlayer.stop();
    _durationSubscription?.cancel();
    _positionSubscription?.cancel();
    _playerCompleteSubscription?.cancel();
    _playerErrorSubscription?.cancel();
    _playerStateSubscription?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return new Column(
      mainAxisSize: MainAxisSize.min,
      children: <Widget>[
        new Row(
          mainAxisSize: MainAxisSize.min,
          children: [
            new IconButton(
                onPressed: _isPlaying ? null : () => _play(),
                iconSize: 64.0,
                icon: new Icon(Icons.play_arrow),
                color: Colors.cyan),
            new IconButton(
                onPressed: _isPlaying ? () => _pause() : null,
                iconSize: 64.0,
                icon: new Icon(Icons.pause),
                color: Colors.cyan),
            new IconButton(
                onPressed: _isPlaying || _isPaused ? () => _stop() : null,
                iconSize: 64.0,
                icon: new Icon(Icons.stop),
                color: Colors.cyan),
          ],
        ),
        new Row(
          mainAxisSize: MainAxisSize.min,
          children: [
            new Padding(
              padding: new EdgeInsets.all(12.0),
              child: new Stack(
                children: [
                  new CircularProgressIndicator(
                    value: 1.0,
                    valueColor: new AlwaysStoppedAnimation(Colors.grey[300]),
                  ),
                  new CircularProgressIndicator(
                    value: (_position != null &&
                            _duration != null &&
                            _position.inMilliseconds > 0 &&
                            _position.inMilliseconds < _duration.inMilliseconds)
                        ? _position.inMilliseconds / _duration.inMilliseconds
                        : 0.0,
                    valueColor: new AlwaysStoppedAnimation(Colors.cyan),
                  ),
                ],
              ),
            ),
            new Text(
              _position != null
                  ? '${_positionText ?? ''} / ${_durationText ?? ''}'
                  : _duration != null ? _durationText : '',
              style: new TextStyle(fontSize: 24.0),
            ),
          ],
        ),
        new Text("State: $_audioPlayerState")
      ],
    );
  }

  void _initAudioPlayer() {
    _audioPlayer = new AudioPlayer(mode: mode);

    _durationSubscription =
        _audioPlayer.onDurationChanged.listen((duration) => setState(() {
              _duration = duration;
            }));

    _positionSubscription =
        _audioPlayer.onAudioPositionChanged.listen((p) => setState(() {
              _position = p;
            }));

    _playerCompleteSubscription =
        _audioPlayer.onPlayerCompletion.listen((event) {
      _onComplete();
      setState(() {
        _position = _duration;
      });
    });

    _playerErrorSubscription = _audioPlayer.onPlayerError.listen((msg) {
      print('audioPlayer error : $msg');
      setState(() {
        _playerState = PlayerState.stopped;
        _duration = new Duration(seconds: 0);
        _position = new Duration(seconds: 0);
      });
    });

    _audioPlayer.onPlayerStateChanged.listen((state) {
      if (!mounted) return;
      setState(() {
        _audioPlayerState = state;
      });
    });
  }

  Future<int> _play() async {
    final playPosition = (_position != null &&
            _duration != null &&
            _position.inMilliseconds > 0 &&
            _position.inMilliseconds < _duration.inMilliseconds)
        ? _position
        : null;
    final result = await _audioPlayer.play(url,
        isLocal: isLocal, position: Duration(seconds: 2));
    if (result == 1) setState(() => _playerState = PlayerState.playing);
    return result;
  }

  Future<int> _pause() async {
    final result = await _audioPlayer.pause();
    if (result == 1) setState(() => _playerState = PlayerState.paused);
    return result;
  }

  Future<int> _stop() async {
    final result = await _audioPlayer.stop();
    if (result == 1) {
      setState(() {
        _playerState = PlayerState.stopped;
        _position = new Duration();
      });
    }
    return result;
  }

  void _onComplete() {
    setState(() => _playerState = PlayerState.stopped);
  }
}