使用bloc更改屏幕

Question

我正在尝试使用bloc切换屏幕(无状态小部件)，当使用BlocBuilder根据状态输出不同的小部件时，上下文将更改为显示的新小部件。在新的小部件中调用状态侦听器。

当状态改变时，我设法显示了一个小部件，问题是当状态再次改变时，上下文被改变，并且在所显示的小部件中调用构建器函数。

因此，我创建了一个包含该块的inheritedWidget，这样我就可以从子部件中分派一个事件在父部件上发生，然后根据状态显示不同的部件。

class SignupViewManager extends InheritedWidget {
  final SignupBloc bloc;
  final Widget child;

  SignupViewManager({Key key, this.child, this.bloc}) : super(key: key, child: child);

  static SignupViewManager of(BuildContext context) {
    return (context.inheritFromWidgetOfExactType(SignupViewManager) as SignupViewManager);
  }

  @override
  bool updateShouldNotify(SignupViewManager oldWidget) {
    return true;
  }
}

class SignupHomePage extends StatelessWidget {
  final SignupBloc signupBloc = SignupBloc();

  SignupHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return SignupViewManager(
        bloc: SignupBloc(),
        child: BlocProvider<SignupBloc>(
          builder: (context) => signupBloc,
          child: BlocBuilder<SignupBloc, SignupState>(
              builder: (context, state) => _signupBuilder(context, state),
              condition: (previousState, state) => _signupCondition(previousState, state),
        ),
      )
    );
  }

  Widget _signupBuilder(BuildContext context, SignupState state) {
    print("IN SIGNUP MAIN BUILDER $state");
    // Changing the UI based on the current state
    if (state is SignupInitial) { // Show credentials for initial state
      return SignupCredentials();
    } else if (state is SavedCredentials) { // Show Agreements after credentials has been saved.
      return SignupAgreements(user: state.user);
    }

    return Text("default");
  }
}

class SignupCredentials extends StatelessWidget {
  SignupBloc signupBloc;

  void _signup(email, password, confirmPassword) {
    if(password == confirmPassword) {
      signupBloc.add(SaveCredentials(email, password));
    } else {
      print("passwords do not match");
    }
  }

  Widget _bloc() {
    return BlocBuilder<SignupBloc, SignupState>(
        builder: (context, state) {
            print("IN SIGNUP credentials builder $state");

            if(state is SavedCredentials) {
            return SignupDetails();
            }

            return Text("${state.runtimeType}");
        },
    );
  }
}

因此，当状态设置为SignupInitial时，应该会出现SignupCredentials无状态小部件。然后，当用户输入凭据并提交它们时，将调度SavedCredentials事件，并显示SignupAgreements。但实际情况是，SignupCredentials构建器接收的是新状态，而不是SignupHomePage。

Answer 1

我解决了这个问题。

我将块提供程序更改为SignupBloc类型。

@override
  Widget build(BuildContext context) {
    return AuthenticationPageLayout(
      color: Colors.white,
      opacity: 0.05,
      child: SignupViewManager(
        child: BlocProvider<SignupBloc>(
            builder: (context) => SignupBloc(),
            child: BlocListener<SignupBloc, SignupState>(
                listener: (context, state) => _signupListener(context, state),
                condition: (previousState, state) => _signupCondition(previousState, state),
                child: BlocBuilder<SignupBloc, SignupState>(
                builder: (context, state) => _signupBuilder(context, state),
                condition: (previousState, state) => _signupCondition(previousState, state),
                )
            )
        );
      )
    );
  }

然后，我使用下面这行代码引用了块提供程序

BlocProvider.of<SignupBloc>(context)