我对 dart 和扑翼还比较陌生。我想创建一个基本块，它可以由另一个扩展，以继承和/或覆盖基本块中定义的事件，并提供自己的事件。让一个块扩展另一个块似乎很好，直到我尝试在BlocBuilder中使用扩展块。在我的示例中，基本块称为BlocABloc，子块称为BlocBBloc。
我得到一个错误，它说：
“BlocBBloc”不符合类型参数“B”的绑定“StateStreamable”。尝试使用是或'StateStreamable'的子类的类型
如果扩展区块不被禁止，我可能会错过什么，导致这不工作？谢谢。我的消息来源在下面。

A源块

import 'package:equatable/equatable.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
class BlocABloc extends Bloc<BlocAEvent, BlocAState> {
  BlocABloc(BlocAInitial blocAInitial) : super(const BlocAInitial(count: 0)) {
    on<Increment>((event, emit) {
      emit(BlocAState(count: state.count + 1));
    });
  }
}
class BlocAState extends Equatable {
  const BlocAState({required this.count});
  final int count;
  @override
  List<Object> get props => [count];
}
final class BlocAInitial extends BlocAState {
  const BlocAInitial({required super.count});
}
class BlocAEvent extends Equatable {
  const BlocAEvent();
  @override
  List<Object> get props => [];
}
final class Increment extends BlocAEvent {}

B组来源

import '../bloc_a/bloc_a_bloc.dart';
class BlocBBloc extends BlocABloc {
  BlocBBloc() : super(const BlocAInitial(count: 0)) {
    on<BlocBEvent>((event, emit) {
      // TODO: implement event handler
    });
  }
}
sealed class BlocBState extends BlocAState {
  const BlocBState({required super.count});
  @override
  List<Object> get props => [];
}
final class BlocBInitial extends BlocBState {
  const BlocBInitial({required super.count});
}
sealed class BlocBEvent extends BlocAEvent {
  const BlocBEvent();
  @override
  List<Object> get props => [];
}

主要

import 'package:bloc_extended/bloc_a/bloc_a_bloc.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'bloc_b/bloc_b_bloc.dart';
void main() {
  runApp(const MyApp());
}
class MyApp extends StatelessWidget {
  const MyApp({super.key});
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const _Home(key: Key('home')),
    );
  }
}
class _Home extends StatelessWidget {
  const _Home({super.key});
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('BLoC')),
      body: BlocProvider<BlocBBloc>(
        create: (_) => BlocBBloc(),
        child: BlocBuilder<BlocBBloc, BlocBState>(  ///<------ ERROR HERE
          builder: (context, state) {
            return Column(
              children: [
                Center(child: Text('${state.count}')),
                FloatingActionButton(
                  onPressed: () {
                    context.read<BlocBBloc>().add(Increment());
                  },
                  child: const Icon(Icons.add),
                ),
              ],
            );
          },
        ),
      ),
    );
  }
}