dart - flutter - bloc - 如何在我的 Ui 中使用 FutureBuilder 来正确实现 Bloc Architecture

Question

我是 Flutter 和 Bloc 架构的新手，我正在尝试使用 Bloc 来实现我的登录功能。我正在尝试调用我的 Bloc 文件中的函数，但我不知道该怎么做。如果您能帮我看看我在使用 Bloc 时是否还有其他问题，我也会很高兴。这是我的用户界面的代码:

MaterialButton(
                      color: Colors.deepPurple,
                      minWidth: screenAwareSize(500, context),
                      onPressed: () {
                        _submitForm(authBloc, user, pass);
                      },
 void _submitForm(AuthBloc authBloc, String user, String pass) async {
    formKey.currentState.save();
    if (formKey.currentState.validate()) {
      var response = await authBloc.login(user, pass);
//when I print(response) it shows null


    }
  }

这是我的 bloc 类:

class AuthBloc extends MainBloc {
  final Repo _repo = Repo();
  PublishSubject<Future<UserModel>> _authController = new PublishSubject<Future<UserModel>>();
  Observable<Future<UserModel>> get auth => _authController.stream;
  login(String user, String pass) async {

    Future<UserModel> item = await _repo.login(user, pass);
    _authController.sink.add(item);
  }

  dispose() {
    _authController.close();
  }
}

AuthBloc authBloc = new AuthBloc();

这是我的 API 类:

class API{
 Future<UserModel> login(String user, String pass) async {
    var response =
        await client.get(base_url + "login.php?user=${user}&pass=${pass}");
    return UserModel.fromJSON(json.decode(response.body));
  }}

这是我的 repo 类:

 class Repo {
    final API api = new API();
  login(String user, String pass) async => await api.login(user, pass);}

Answer 1

我将尝试首先解释 BLOC 组件应该做什么，尽可能简短(并且尽可能简单)。

• UI 屏幕 - 显然向用户显示数据
• BLOC(或 ViewModel)- 决定如何向用户显示数据，是否将文本加粗，是否显示错误，是否转到下一个屏幕。
• Repo - 决定向用户显示什么数据(我们是否显示来自数据库的内容，我们是否从 API 获取内容，我们是否显示红色的产品？)

根据您的应用的功能，您还可以拥有其他组件，例如:

• 网络 - 执行 API 请求并将响应转换为模型，这应该只能从存储库访问，并且该组件唯一应该做的就是从存储库接收数据( header 、正文、url)并将数据返回到存储库模型的形式(您可以查看下面的代码)。
• 数据库 - 对数据库执行 CRUD 操作，同样只能从 repo 访问。
• 传感器 - 从本地传感器读取数据，同样只能从存储库访问。

现在，我建议也将 BLOC 模式与依赖注入(inject)一起使用，没有它就有点没用了。使用 DI，您可以模拟所有组件直到 UI，并且可以非常容易地对所有代码进行单元测试。

此外，我认为没有必要将 RxDart(库)与 Streams/Future(相当于 RxDart lib 的 dart)混合使用。首先，我建议只使用其中一个，并根据您的代码片段，我建议更好地了解如何整体使用 Rx。

所以，下面有一个小代码片段，说明我将如何使用 block 模式进行登录(最好也检查代码注释 :))。

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;

class TheUIScreen extends StatefulWidget {
  @override
  _TheUIScreenState createState() => _TheUIScreenState();
}

class _TheUIScreenState extends State<TheUIScreen> {
  //TODO: for repo, block, networking, we used dependecy injection, here we have to create and init all the dependecies;

  TheAuthBlock _block;

  @override
  void initState() {
    super.initState();
    TheAuthAPI api = TheAuthAPI();
    TheAuthRepo repo =
        TheAuthRepo(theAuthAPI: api); // we could also do repo = TheAuthRepo();
    _block =
        TheAuthBlock(repo: repo); // we could also do _block = TheAuthBlock();
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: RaisedButton(onPressed: () {
        _block.loginUser("test", "test").then((actualUser) {
          Navigator.of(context).push(MaterialPageRoute(builder: (context) {
            return TestRoute(); // or do whatever action you need, the user is logged in
          }));
        }).catchError((error) {
          //show error, something went wrong at login;
        });
      }),
    );
  }
}

class TheAuthBlock {
  final TheAuthRepo repo;

  TheAuthBlock({this.repo = const TheAuthRepo()});

  Future<UserModel> loginUser(String email, String password) {
    return repo.login(email, password).then((userModel) {
      //TODO: here we decide HOW to display the user, you might want to transfor the UserModel into a model that's used only for UI.
      //In any way, here you should do all the processing, the UI only should only display the data, not manipulate it.
    });
  }
}

class TheAuthRepo {
  final TheAuthAPI theAuthAPI;

  const TheAuthRepo(
      {this.theAuthAPI =
          const TheAuthAPI()}); // THIS would be the default constructor but it will alow us to test it using unit tests.

  Future<UserModel> login(String email, String password) {
    //TODO: here you could also check if the user is already logged in and send the current user as a response
    if (email.isNotEmpty && password.isNotEmpty) {
      return theAuthAPI.login(email, password).then((userModel) {
        //TODO: you can do extra processing here before returning the data to the block;
      });
    } else {
      return Future.error(
          "Well you can't login with empty ddata"); // TODO: you can return differetn errors for email or pwd;
    }
  }
}

class TheAuthAPI {
  final String url;

  const TheAuthAPI({this.url = "https://my.cool.api/login"});

  Future<UserModel> login(String email, String pwd) {
    // TODO: note you return a future from this method since the login will return only once (like almost all http calls)
    Map<String, String> headers = Map(); // TODO: set any headers you need here
    Map<String, String> body = {
      "email": email,
      "pwd": pwd
    }; // TODO: change the body acordingly
    return http.post("THE URL", headers: headers, body: body).then((response) {
      //TODO: parse response here and return it
      return UserModel("test",
          "test"); // this should be generated from the response not like this
    });
  }
}

class UserModel {
  final String email;

  UserModel(this.email, this.pass);

  final String pass;
}