BlocBuilder会更改状态，但不会更改屏幕上的文本

import 'package:flutter_bloc/flutter_bloc.dart';

abstract class CounterEvent {}

class IncrementEvent extends CounterEvent {}

class CounterState {
  final int count;
  CounterState(this.count);
}

class CounterBloc extends Bloc<CounterEvent, CounterState> {
  CounterBloc() : super(CounterState(0));

  @override
  Stream<CounterState> mapEventToState(CounterEvent event) async* {
    if (event is IncrementEvent) {
      yield CounterState(state.count + 1);
    }
  }
}

BlocBuilder<CounterBloc, CounterState>(
  builder: (context, state) {
    return Text('Count: ${state.count}');
  },
),

BlocBuilder<CounterBloc, CounterState>(
  key: ValueKey(state.count), // 使用状态的某个唯一值作为 Key
  builder: (context, state) {
    return Text('Count: ${state.count}');
  },
),