Bloc 发出状态问题

Question

import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:moms/features/chat/domain/entities/message_entity.dart';
import 'package:moms/features/chat/domain/usecases/send_message.dart';
import 'package:moms/features/chat/domain/usecases/get_messages.dart';
import 'package:moms/features/chat/domain/usecases/get_or_create_thread_usecase.dart';

part 'chat_event.dart';
part 'chat_state.dart';

class ChatBloc extends Bloc<ChatEvent, ChatState> {
  final GetOrCreateThread getOrCreateThread;
  final GetMessages getMessages;
  final SendMessage sendMessage;

  ChatBloc({
    required this.getOrCreateThread,
    required this.getMessages,
    required this.sendMessage,
  }) : super(ChatInitial()) {
    on<LoadChatThreadEvent>(_onLoadChatThreadEvent);
    on<LoadMessagesEvent>(_onLoadMessagesEvent);
    on<SendMessageEvent>(_onSendMessageEvent);
  }

  Future<void> _onLoadChatThreadEvent(
      LoadChatThreadEvent event, Emitter<ChatState> emit) async {
    emit(ChatLoading());

    final threadResult = await getOrCreateThread(event.gigId, event.bidId);
    threadResult.fold(
      (failure) =>
          emit(ChatError('Failed to load chat thread: ${failure.message}')),
      (threadId) async {
        await _loadMessagesForThread(threadId, emit);
      },
    );
  }

  Future<void> _onLoadMessagesEvent(
      LoadMessagesEvent event, Emitter<ChatState> emit) async {
    emit(ChatLoading());
    await _loadMessagesForThread(event.threadId, emit);
  }

  Future<void> _onSendMessageEvent(
      SendMessageEvent event, Emitter<ChatState> emit) async {
    emit(ChatLoading());

    final sendResult =
        await sendMessage(event.threadId, event.content, event.senderId);
    sendResult.fold(
      (failure) =>
          emit(ChatError('Failed to send message: ${failure.message}')),
      (message) async {
        await _loadMessagesForThread(event.threadId, emit);
      },
    );
  }

  Future<void> _loadMessagesForThread(
      int threadId, Emitter<ChatState> emit) async {
    final messagesResult = await getMessages(threadId);
    messagesResult.fold(
      (failure) =>
          emit(ChatError('Failed to load messages: ${failure.message}')),
      (messages) => emit(ChatLoaded(threadId: threadId, messages: messages)),
    );
  }
}

对于上面的 chat_bloc 代码，我收到错误：

E/flutter (18794): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: 'package:bloc/src/emitter.dart': Failed assertion: line 114 pos 7: '!_isCompleted': 
E/flutter (18794): emit was called after an event handler completed normally.
E/flutter (18794): This is usually due to an unawaited future in an event handler.
E/flutter (18794): Please make sure to await all asynchronous operations with event handlers
E/flutter (18794): and use emit.isDone after asynchronous operations before calling emit() to
E/flutter (18794): ensure the event handler has not completed.
E/flutter (18794): 
E/flutter (18794):   **BAD**
E/flutter (18794):   on<Event>((event, emit) {
E/flutter (18794):     future.whenComplete(() => emit(...));
E/flutter (18794):   });
E/flutter (18794): 
E/flutter (18794):   **GOOD**
E/flutter (18794):   on<Event>((event, emit) async {
E/flutter (18794):     await future.whenComplete(() => emit(...));
E/flutter (18794):   });
E/flutter (18794): 
E/flutter (18794): #0      _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:50:61)
E/flutter (18794): #1      _AssertionError._throwNew (dart:core-patch/errors_patch.dart:40:5)
E/flutter (18794): #2      _Emitter.call (package:bloc/src/emitter.dart:114:7)
E/flutter (18794): #3      ChatBloc._loadMessagesForThread.<anonymous closure> (package:project/features/chat/presentation/bloc/chat_bloc.dart:66:25)
E/flutter (18794): #4      Right.fold (package:dartz/src/either.dart:200:64)
E/flutter (18794): #5      ChatBloc._loadMessagesForThread (package:project/features/chat/presentation/bloc/chat_bloc.dart:63:20)
E/flutter (18794): <asynchronous suspension>
E/flutter (18794): #6      ChatBloc._onLoadChatThreadEvent.<anonymous closure> (package:project/features/chat/presentation/bloc/chat_bloc.dart:34:9)
E/flutter (18794): <asynchronous suspension>

我尝试了多种方法来解决，但错误是多余的。

我正在尝试实现聊天功能。后端工作正常，但集团在发出时重复给出此错误。另外，我在这里没有使用网络套接字。

我是 bloc 新手，因此发现很难解决此错误。

Answer 1

尝试集体进行此更改：

 Future<void> _onSendMessageEvent(
    SendMessageEvent event, 
    Emitter<ChatState> emit,
 ) async {
      ... ...
      (message) async {
        // await _loadMessagesForThread(event.threadId, emit); <- remove
        add(LoadMessagesEvent(event.threadId));
      },
    );
  }
...
  Future<void> _onSendMessageEvent(
      SendMessageEvent event, 
      Emitter<ChatState> emit,
  ) async {
    ... ...
      (message) async {
        //await _loadMessagesForThread(event.threadId, emit); <-- remove
        add(LoadMessagesEvent(event.threadId));
      },
    );
  }