Flutter Toogle最受欢迎的onDismissable活动，与Bloc一起颤振

我在完成有关如何从列表中添加/删除（切换）收藏夹（来自api响应）的操作时遇到一些问题。实际上，我可以将收藏夹添加到列表中，也可以以单独的方式将其删除，但我不能以切换方式使用相同的按钮。简而言之，它正在工作，但我无法正确实现切换操作。请看一下代码，看看是否有一个很好的方法可以在不使用setstate的情况下实现切换

关闭按钮（从列表中删除）

同一个按钮实现通过Bloc向列表添加收藏夹

CupertinoButton(
                        padding: EdgeInsets.zero,
                        minSize: 30,
                        onPressed: () {
                          masterBloc.add(MasterAddToFavorites(item));
                        },
                        child: CircleContainer(
                          child: Icon(
                            item.isFavorite
                                ? Icons.favorite
                                : Icons.favorite_border,
                            color: Colors.white,
                          ),
                          size: 35,
                        ),
                      ),

项目定义

class YoutbeVideo {
  final String videoId, title, description, banner;
  bool isFavorite;

  YoutbeVideo(
      {@required this.videoId,
      @required this.title,
      @required this.description,
      @required this.banner,
      this.isFavorite});

  void toggleFavoriteStatus() {
    isFavorite = !isFavorite;
  }

分为3个文件的集团代码

大师集团

import 'package:bloc/bloc.dart';
import 'package:documentales_app/models/youtube_video.dart';
import 'master_events.dart';
import 'master_state.dart';

class MasterBloc extends Bloc<MasterEvents, MasterState> {
  @override
  MasterState get initialState => MasterState.initialState();

  @override
  Stream<MasterState> mapEventToState(MasterEvents event) async* {
    if (event is MasterSetTab) {
      yield this.state.copyWith(currentTab: event.tab);
    } else if (event is MasterAddToHistory) {
      yield* _addToHistory(event);
    } else if (event is MasterRemoveFromHistory) {
      yield* _removeFromHistory(event);
    } else if (event is MasterRemoveFromFavorites) {
      yield* _removeFromFavorites(event);
    } else if (event is MasterLogout) {
      yield this.state.copyWith(history: [], currentTab: 0);
    } else if (event is MasterAddToFavorites) {
      yield* _addToFavorites(event);
    }
  }

  Stream<MasterState> _addToHistory(MasterAddToHistory event) async* {
    final int index = this
        .state
        .history
        .indexWhere((item) => item.videoId == event.youtubeVideo.videoId);

    if (index == -1) {
      final history = List<YoutubeVideo>.from(this.state.history);
      history.add(event.youtubeVideo);

      yield this.state.copyWith(history: history);
    }
  }

  Stream<MasterState> _addToFavorites(MasterAddToFavorites event) async* {
    final int index = this
        .state
        .favorites
        .indexWhere((item) => item.videoId == event.youtubeVideo.videoId);

    if (index == -1) {
      final favorites = List<YoutubeVideo>.from(this.state.favorites);
      favorites.add(event.youtubeVideo);

      yield this.state.copyWith(favorites: favorites);
    }
  }

  Stream<MasterState> _removeFromHistory(MasterRemoveFromHistory event) async* {
    final history = List<YoutubeVideo>.from(this.state.history);
    history.removeAt(event.index);
    yield this.state.copyWith(history: history);
  }

  Stream<MasterState> _removeFromFavorites(
      MasterRemoveFromFavorites event) async* {
    final favorites = List<YoutubeVideo>.from(this.state.favorites);
    favorites.removeAt(event.index);
    yield this.state.copyWith(favorites: favorites);
  }
}

---

所以执行切换的一种方法是用一个事件替换添加和删除事件。所以你可以摆脱这些事件：

class MasterAddToFavorites extends MasterEvents {
  final YoutubeVideo youtubeVideo;

  MasterAddToFavorites(this.youtubeVideo);
}

class MasterRemoveFromFavorites extends MasterEvents {
  final int index;

  MasterRemoveFromFavorites(this.index);
}

并将其替换为：

class MasterToggleInFavorites extends MasterEvents {
  final YoutubeVideo video;

  MasterToggleInFavorites(video);
}

接下来，在bloc内部，在处理该事件的方法内部，您可以执行如下操作：

Stream<MasterState> _toggleInFavorites(MasterToggleInFavorites event) async* {
    final int index = this
        .state
        .favorites
        .indexWhere((item) => item.videoId == event.youtubeVideo.videoId);

    if (index == -1) {
      final favorites = List<YoutubeVideo>.from(this.state.favorites);
      favorites.add(event.youtubeVideo);
      event.youtubeVideo.isFavourite = true;

      yield this.state.copyWith(favorites: favorites);
    } else {
      final favorites = List<YoutubeVideo>.from(this.state.favorites);
      favorites.removeAt(index);
      event.youtubeVideo.isFavourite = false;

      yield this.state.copyWith(favorites: favorites);
    }

Stream\u toggleInFavorites（MasterToggleInFavorites事件）异步*{
最终int索引=此
.州
.最爱
.indexWhere（（项）=>item.videoId==event.youtubeVideo.videoId）；
如果（索引==-1）{
最终收藏夹=List.from（this.state.favorites）；
收藏夹。添加（event.youtubeVideo）；
event.youtubeVideo.isfavorite=true；
生成此.state.copyWith（收藏夹：收藏夹）；
}否则{
最终收藏夹=List.from（this.state.favorites）；
收藏夹.removeAt（索引）；
event.youtubeVideo.isfavorite=false；
生成此.state.copyWith（收藏夹：收藏夹）；
}

视频课程

class YoutubeVideo {
  final String videoId, title, description, banner;
  bool isFavorite;

  YoutubeVideo(
      {@required this.videoId,
      @required this.title,
      @required this.description,
      @required this.banner,
      this.isFavorite = false});

  factory YoutubeVideo.fromJson(Map<String, dynamic> json,
      {bool fromPlayList = false}) {
    final snippet = json['snippet'];
    final thumbnail =
        snippet['thumbnails']['standard'] ?? snippet['thumbnails']['high'];

    String videoId;

    if (!fromPlayList) {
      videoId = json['contentDetails']['videoId'];
    } else {
      videoId = snippet['resourceId']['videoId'];
    }

    return YoutubeVideo(
        videoId: videoId,
        title: snippet['title'],
        description: snippet['description'],
        banner: thumbnail['url']);
  }
}

---

你也可以在bloc中共享代码吗？在bloc文件中添加了代码，谢谢！如果不是添加和删除两个单独的状态，而是有一个和该状态的bloc将签入列表，如果对象已经存在，如果存在，则将其从列表中删除，如果没有，则将其添加到列表中。是的，我一直在考虑，但我没有找不到方法。它工作得很好。但是仍然无法根据切换的变化反映图标中的变化来显示颜色。尝试创建一些包装类，其中包含两个字段：视频和bool，如果它是最喜欢的或不喜欢的。我已经添加了上面的类和按钮，以防你看到代码。出于任何原因儿子，我错过了一些东西，因为它没有反映颜色的变化。我是新来的，所以如果这是一个noob问题，请容忍我。是的，我知道，这是我无法实现的。它可能看起来很简单，但我对它感到疯狂，因为我尝试了许多不同的方法，并在它上结巴。非常感谢！我更新了我的帖子，看看!InFavorites方法您只需在按下按钮时在YouTube设备上设置

isFavorite

bool即可。

class MasterToggleInFavorites extends MasterEvents {
  final YoutubeVideo video;

  MasterToggleInFavorites(video);
}

Stream<MasterState> _toggleInFavorites(MasterToggleInFavorites event) async* {
    final int index = this
        .state
        .favorites
        .indexWhere((item) => item.videoId == event.youtubeVideo.videoId);

    if (index == -1) {
      final favorites = List<YoutubeVideo>.from(this.state.favorites);
      favorites.add(event.youtubeVideo);
      event.youtubeVideo.isFavourite = true;

      yield this.state.copyWith(favorites: favorites);
    } else {
      final favorites = List<YoutubeVideo>.from(this.state.favorites);
      favorites.removeAt(index);
      event.youtubeVideo.isFavourite = false;

      yield this.state.copyWith(favorites: favorites);
    }

class YoutubeVideo {
  final String videoId, title, description, banner;
  bool isFavorite;

  YoutubeVideo(
      {@required this.videoId,
      @required this.title,
      @required this.description,
      @required this.banner,
      this.isFavorite = false});

  factory YoutubeVideo.fromJson(Map<String, dynamic> json,
      {bool fromPlayList = false}) {
    final snippet = json['snippet'];
    final thumbnail =
        snippet['thumbnails']['standard'] ?? snippet['thumbnails']['high'];

    String videoId;

    if (!fromPlayList) {
      videoId = json['contentDetails']['videoId'];
    } else {
      videoId = snippet['resourceId']['videoId'];
    }

    return YoutubeVideo(
        videoId: videoId,
        title: snippet['title'],
        description: snippet['description'],
        banner: thumbnail['url']);
  }
}

CupertinoButton(
                        padding: EdgeInsets.zero,
                        minSize: 30,
                        onPressed: () {
                          masterBloc.add(MasterToggleInFavorites(item));
                        },
                        child: CircleContainer(
                          child: Icon(
                            //Icons.playlist_add,
                            item.isFavorite
                                ? Icons.favorite_border
                                : Icons.favorite,
                            color: Colors.white,
                          ),
                          size: 35,
                        ),
                      ),