Using Stream for counter maybe too complicated for beginning.

[killvung]

So using StreamController to store the count state and display it with StreamBuilder and AsyncSnapshot in the UI are really complicated for Flutter beginner without BloC experience. For me I would simply storing the count state as an int and registering events under the bloc class with on instead of mapping them, then display it with context
For example

class CounterBloc extends Bloc<CounterEvent, CounterState> {
  CounterBloc() : super(const Counter(0)) {
    on<CounterIncrementPressed>(
        (event, emit) => emit(Counter(state.count + 1)));
    on<CounterDecrementPressed>(
        (event, emit) => emit(Counter(state.count - 1)));

    on<CounterResetPressed>((event, emit) => emit(const Counter(0)));
  }
}

Then in UI

body: Center(
        child: BlocBuilder<CounterBloc, int>(
          builder: (context, count) {
            return Text('$count', style: textTheme.headline2);
          },
        ),
      ),