Question

我正在尝试如何处理Android中的dagger 2和干净架构的依赖注入。我想要实现的是当我点击一个按钮时，一条消息将被保存到Firebase数据库。并向用户显示成功消息。当我构建我的项目时，我收到了这个错误：

错误：（10,1）错误：com.example.mvpsample.home.HomeComponent （unscoped）可能不会引用作用域绑定：@Provides @Singleton com.google.firebase.database.FirebaseDatabase com.example.mvpsample.data.DataModule.provideFirebaseDatabase（）

这是我的app类：

public class MyApp extends Application {

    private static MyApp app;
    private HomeComponent homeComponent;
    private AuthenticationComponent authenticationComponent;

    @Inject
    Presenter presenter;

    @Override
    public void onCreate() {
        super.onCreate();
        app = this;

        homeComponent = DaggerHomeComponent
                .builder()
                .homeModule(new HomeModule(presenter.getView()))
                .build();
    }

    public HomeComponent getHomeComponent() {
        return homeComponent;
    }

    public static MyApp app() {
        return app;
    }
}

HomeActivity

public class HomeActivity extends AppCompatActivity implements BaseContract.View {

    @Inject
    public Presenter presenter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);

        MyApp
                .app()
                .getHomeComponent()
                .inject(this);

    }

    @OnClick(R.id.tvHello)
    public void clickTvHello() {
        presenter.writeStringToDatabase("Hi");
    }


    @Override
    public void showSuccessMessage() {
        Toast.makeText(this, "Success", Toast.LENGTH_SHORT).show();
    }
}

HomeModule

@Module
public class HomeModule {

    private final BaseContract.View View;

    @Inject
    public HomeModule(BaseContract.View View) {
        this.View = View;
    }

    @Provides
    public BaseContract.View provideView() {
        return View;
    }
}

HomeComponent

@Component(modules = {HomeModule.class, DataModule.class})
public interface HomeComponent {
    void inject(HomeActivity homeActivity);
}

DataModule的

@Module
public class DataModule {

    @Provides
    @Singleton
    public FirebaseDatabase provideFirebaseDatabase() {
        return FirebaseDatabase.getInstance();
    }
}

BaseContract

public interface BaseContract {
    interface View {
        void showSuccessMessage();
    }

    interface Presenter {

        View getView();

        void writeStringToDatabase(String string);
    }
}

演示

public class Presenter implements BaseContract.Presenter {

    private final BaseContract.View View;

    @Inject
    FirebaseDatabase firebaseDatabase;

    @Inject
    public Presenter(BaseContract.View View) {
        this.View = View;
    }


    @Override
    public BaseContract.View getView() {
        return View;
    }

    @Override
    public void writeStringToDatabase(String string) {
        firebaseDatabase.getReference()
                .child("messages")
                .push()
                .child("value")
                .setValue(string).addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void aVoid) {
                getView().showSuccessMessage();
            }
        });
    }
}

我遵循了示例项目和教程，但不明白我在这里做错了什么。不是在寻找工作项目，但我想了解什么是最佳实践，以及如何管理和使用模块和组件。

Answer 1

问题是当HomeComponent提供范围内的依赖关系（即DataModule依赖关系）时，FirebaseDatabase不是作用域的。

非作用域组件不能依赖作用域提供程序。您必须删除@Singleton提供商处的provideFirebaseDatabase()或在@Singleton上添加HomeComponent。

Android Dagger 2和干净的架构实现，范围错误

1 个答案: