发出新状态时 Cubit 不会重建

Question

每当我调用toggleLocked 事件时，BlocBuilder 都不会重建小部件。

我在互联网上查了很多资料，发现了这个解释：/sf/answers/4260843121/ 我认为在某个地方我错误地使用了 equatable 包，导致 BlocBuilder 认为没有任何改变（虽然是有）。

我已阅读 Bloc 库中的常见问题解答，并且提供的三个解决方案（可等同/不重用相同状态/使用 fromList 的道具）似乎无法解决问题。

我的肘：

class LockCubit extends Cubit<LockState> {
  LockCubit({@required this.repository})
      : assert(repository != null),
        super(LockInitial());

  final LocksRepository repository;

  Future<void> fetch() async {
    try {
      final locks = await repository.fetchLocks();
      emit(LocksDisplayed().copyWith(locks));
    } on Exception {
      emit(LockError());
    }
  }

  Future<void> toggleLocked(int id) async {
    try {
      final locks = await repository.toggleLocked(id);
      emit(LocksDisplayed().copyWith(List.from(locks)));
    } on Exception {
      emit(LockError());
    }
  }
}

我的状态：

abstract class LockState extends Equatable {
  const LockState();

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

class LockInitial extends LockState {
  @override
  String toString() => 'LocksUninitialized';
}

class LockError extends LockState {
  @override
  String toString() => 'LockError';
}

class LocksDisplayed extends LockState {
  final List<Lock> locks;

  const LocksDisplayed([this.locks = const []]);

  LocksDisplayed copyWith(locks) => LocksDisplayed(locks ?? this.locks);

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

  @override
  String toString() => 'LocksDisplayed { locks: $locks }';
}

我的型号：

class Lock extends Equatable {
  Lock({this.id, this.name, this.locked, this.displayed});

  final int id;
  final String name;
  final bool locked;
  final bool displayed;

  @override
  String toString() =>
      'Lock { id: $id name: $name locked: $locked displayed: $displayed }';

  Lock copyWith({id, name, locked, displayed}) => Lock(
      id: id ?? this.id,
      name: name ?? this.name,
      locked: locked ?? this.locked,
      displayed: displayed ?? this.displayed);

  @override
  List<Object> get props => [id, name, locked, displayed];
}

我的存储库：

class LocksRepository {
  List<Lock> locks = [];

  Future<List<Lock>> fetchLocks() async {
    // This is a temporary implementation
    // In the future the data should be fetched from a provider

    locks = [
      new Lock(
        id: 0,
        name: 'Voordeur',
        locked: false,
      ),
      new Lock(
        id: 1,
        name: 'Achterdeur',
        locked: false,
      )
    ];

    return locks;
  }

  Future<List<Lock>> toggleLocked(int id) async {
    // This is a temporary implementation
    // In the future a request to change a lock should be made and then the specific lock should be retrieved back and edited.

    locks[id] = locks[id].copyWith(locked: !locks[id].locked);

    return locks;
  }
}

我正在使用以下触发器更改状态：

context.read<LockCubit>().toggleLocked(focusedIndex);

我正在使用 BlocBuilder 像这样来构建状态：

BlocBuilder<LockCubit, LockState>(builder: (context, state) {
      print('State Changed');

      if (state is LockInitial) {
        return Text('lockInitial');
      }

      if (state is LocksDisplayed) {
        return Swiper(
            itemBuilder: (BuildContext context, int index) {
              return Column(
                children: [
                  Text(state.locks[index].name),
                  Text(state.locks[index].locked.toString())
                ],
              );
            },
            onIndexChanged: onIndexChanged,
            loop: true,
            itemCount: state.locks.length);
      }

      if (state is LockError) {
        return Text('lockError');
      }

      return Container();
    });

非常感谢所有帮助。

Answer 1

你能检查一下 BlocProvider 吗？我遇到了同样的问题。如果此块位于materialApp内，则必须传递BlocProvider.value而不是在小部件中创建。