[英]Emiting a change state in my cubit doesn't produce an event for my listener
[英]Cubit not rebuilding when emiting a new state
每当我调用 toggleLocked 事件时,BlocBuilder 都不会重建小部件。
我在互联网上看了很多,发现了这个解释: https://stackoverflow.com/a/60869187/3290471我认为在某个地方我错误地使用了平等的 package,这导致 BlocBuilder 认为没有任何改变(虽然是有)。
我已经阅读了 Bloc libray 中的常见问题解答,并且三个提供的解决方案(平等的道具/不重用相同的 state/使用 fromList)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 model:
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 state:
context.read<LockCubit>().toggleLocked(focusedIndex);
我正在使用这样的 BlocBuilder 来构建 state:
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();
});
所有帮助将不胜感激。
你可以检查 BlocProvider 吗? 我遇到了同样的问题。 如果这个 bloc 在 materialApp 中,你必须传递 BlocProvider.value 而不是在小部件中创建。
我有点困惑,如果这可以工作。 但是对于一个集团,您将使用一个事件而不是肘位(即使事件是基于肘位的)。
所以首先我会使用标准模式:state event bloc with mapEventToState
然后,我在你的代码中也没有看到,如果你切换你的锁,它会在伪代码中看起来像这样
if (event is toggleLock) {
yield lockInProgress();
toggleLock();
yield locksDisplayed;
}
这样,您的 state 总是从 locksDisplayed 更改为 lockInProgress 到 locksDisplayed - 正如您在上面的链接中阅读的那样
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