我正在使用 bloc: ^7.0.0 这是目前最新的 bloc 包，现在说听方法现在已被弃用。相反，我应该使用stream.listen。但我不明白如何使用stream.listen。请帮忙解释一下。谢谢！

下面是我的代码：

    signInBloc.l?i?s?t?e?n?((state) {
      if (state is CheckIfSignedInEventCompletedState) {
        if (state.isSignedIn) {
          print('logged in');
        } else {
          print('not logged in');
        }
      }

class SignInBloc extends Bloc<SignInEvent, SignInState> {
  @override
  Stream<SignInState> mapEventToState(
    SignInEvent event,
  ) async* {
    if (event is CheckIfSignedInEvent) {
      yield* mapCheckIfSignedInEventToState();
    }
  }
  Stream<SignInState> mapCheckIfSignedInEventToState() async* {
    try {
      bool isSignedIn = await authenticationRepository.checkIfSignedIn();
      if (isSignedIn != null) {
        if (isSignedIn) {
          yield CheckIfSignedInEventCompletedState(true);
        } else {
          yield CheckIfSignedInEventCompletedState(false);
        }
      } else {
        yield CheckIfSignedInEventFailedState();
      }
    } catch (e) {
      print(e);
      yield CheckIfSignedInEventFailedState();
    }
  }
}

回答

signInBloc.l?i?s?t?e?n?((state) {

signInBloc.stream.listen((state) {