从 3.x 迁移到 bloc 8.0.1，出现折旧错误

Question

我已从 bloc 3.x 版本更新到 8.0.1，但我对 bloc 还很陌生。我已经阅读了基础知识并对其进行了一些编辑，但现在我被困住了。

这是我的事件、集团和状态文件。如何将其转换为与 bloc 8.0.1 兼容的代码。

player_bloc.dart

import 'dart:async';

import 'package:bloc/bloc.dart';
import 'package:equatable/equatable.dart';
import 'package:meta/meta.dart';
import 'package:online_radio/radio/radio_player.dart';
import 'package:online_radio/radio/radio_state.dart';
import 'package:online_radio/station.dart';

part 'player_event.dart';
part 'player_state.dart';

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

  PlayerBloc({@required this.radioPlayer})
      : assert(radioPlayer != null),
        super(StoppedState()) {
    on<PauseEvent>(
      ((event, emit) async{
        
      })
    );
    on<PlayEvent>(
      ((event, emit) async{
        
      })
    );
    
    
    radioPlayer.radioStateStream.listen((radioState) {
      if (radioState == RadioState.PLAYING && state is PausedState) {
        this.add(PlayEvent((state as PausedState).currentStation));
      }
    });
  }


  @override
  Stream<PlayerState> mapEventToState(PlayerEvent event) async* {
    if (event is PlayEvent) {
      yield* _handlePlayEvent(event);
    } else if (event is PauseEvent) {
      yield* _handlePauseEvent(event);
    }
  }

  Stream<PlayerState> _handlePlayEvent(PlayEvent playEvent) async* {
    if (state is StoppedState) {
      _playNewRadioStation(playEvent);
      yield PlayingState(playEvent.station);
    } else if (state is PausedState) {
      if ((state as PausedState).currentStation != playEvent.station) {
        _playNewRadioStation(playEvent);
      } else {
        _playExistingRadioStation();
      }
      yield PlayingState(playEvent.station);
    } else if (state is PlayingState) {
      if ((state as PlayingState).currentStation != playEvent.station) {
        _playNewRadioStation(playEvent);
      } else {
        _playExistingRadioStation();
      }
      yield PlayingState(playEvent.station);
    }
  }

  Stream<PlayerState> _handlePauseEvent(PauseEvent pauseEvent) async* {
    if (state is PlayingState) {
      radioPlayer.pause();
      yield PausedState((state as PlayingState).currentStation);
    }
  }

  void _playExistingRadioStation() {
    radioPlayer.play();
  }

  void _playNewRadioStation(PlayEvent playEvent) {
    radioPlayer.setUrl(playEvent.station.radioUrl).then((_) {
      radioPlayer.play();
    });
  }
}

player_state.dart

part of 'player_bloc.dart';

@immutable
abstract class PlayerState extends Equatable {
  const PlayerState();

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

class StoppedState extends PlayerState {}

class PlayingState extends PlayerState {
  final Station currentStation;

  PlayingState(this.currentStation);
}

class PausedState extends PlayerState {
  final Station currentStation;

  PausedState(this.currentStation);
}

player_event.dart

part of 'player_bloc.dart';

@immutable
abstract class PlayerEvent extends Equatable {
  const PlayerEvent();

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

class PlayEvent extends PlayerEvent {
  final Station station;
  PlayEvent(this.station);

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

class PauseEvent extends PlayerEvent {}

这是我到现在为止的进步。之后我该怎么做？

Answer 1

player_state.dart 和 player_event.dart 不变

尝试更改此 player_bloc.dart 文件：

import 'dart:async';

import 'package:bloc/bloc.dart';
import 'package:equatable/equatable.dart';
import 'package:meta/meta.dart';
import 'package:online_radio/radio/radio_player.dart';
import 'package:online_radio/radio/radio_state.dart';
import 'package:online_radio/station.dart';

part 'player_event.dart';
part 'player_state.dart';

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

  PlayerBloc({@required this.radioPlayer})
      : assert(radioPlayer != null),
        super(StoppedState()) {
    on<PauseEvent>(_onPause);
    on<PlayEvent>(_onPlay);


    radioPlayer.radioStateStream.listen((radioState) {
      if (radioState == RadioState.PLAYING && state is PausedState) {
        this.add(PlayEvent((state as PausedState).currentStation));
      }
    });
  }

  void _onPause(
      PauseEvent event,
      Emitter<PlayerState> emit,
      ) async {
    if(state is PlayingState){
      radioPlayer.pause();
      emit(PausedState((state as PlayingState).currentStation));
    }
  }

  void _onPlay(
      PlayEvent event,
      Emitter<PlayerState> emit,
      ) async {
    if (state is StoppedState) {
      _playNewRadioStation(playEvent);
      emit(PlayingState(playEvent.station));
    } else if (state is PausedState) {
      if ((state as PausedState).currentStation != playEvent.station) {
        _playNewRadioStation(playEvent);
      } else {
        _playExistingRadioStation();
      }
      emit(PlayingState(playEvent.station));
    } else if (state is PlayingState) {
      if ((state as PlayingState).currentStation != playEvent.station) {
        _playNewRadioStation(playEvent);
      } else {
        _playExistingRadioStation();
      }
      emit(PlayingState(playEvent.station));
    }
  }

  void _playExistingRadioStation() {
    radioPlayer.play();
  }

  void _playNewRadioStation(PlayEvent playEvent) {
    radioPlayer.setUrl(playEvent.station.radioUrl).then((_) {
      radioPlayer.play();
    });
  }
}