如果没有 @Provides- 或 @Produces-annotated 方法，则无法提供 Dagger2

Question

所以我正在开发一个具有 mvp 模式的应用程序，但我在使用 Dagger2 时遇到了问题

我已经为演示者创建了一个名为 HelloPresenter 的界面。

然后我为该接口创建了一个名为 HelloPresenterImpl 的实现

我的 HelloPresenter

public interface HelloPresenter {

    public void sayHello();

}

我的 HelloPresenterImpl

public class HelloPresenterImpl implements HelloPresenter {

    StoryView storyView;

    @Inject
    public HelloPresenterImpl(StoryView storyView) {
        this.storyView = storyView;
    }

    @Override
    public void sayHello() {
        Log.d(TAG, "hello there");
    }

}

我的组件

@UserScope
@Component(dependencies = NetComponent.class, modules = RetrofitModule.class)
public interface StoryComponent {
    void inject(MainActivity activity);
    void inject(HelloPresenter helloPresenter);
}

我的模块

@Module
public class HelloModule {

    @Provides
    public HelloPresenter providesHelloPresenter(final HelloPresenterImpl presenter){
        return presenter;
    }

}

我的基础应用程序

public class BaseApplication extends Application {

    private NetComponent mNetComponent;
    private StoryComponent mStoryComponent;

    @Override
    public void onCreate() {
        super.onCreate();

        mNetComponent = DaggerNetComponent.builder()
                .appModule(new AppModule(this))
                .netModule(new NetModule())
                .build();

        mStoryComponent = DaggerStoryComponent.builder()
                .netComponent(mNetComponent)
                .retrofitModule(new RetrofitModule())
                .storyModule(new StoryModule())
                .build();

    }

    public NetComponent getNetComponent() {
        return mNetComponent;
    }

    public StoryComponent getStoryComponent() {
        return mStoryComponent;
    }

现在，当我尝试将它注入到我的 MainActivity 中时，它会抛出一条错误消息

Error:(18, 10) error: com.exampleapp.Hello.presenter.HelloPresenter cannot be provided without an @Provides- or @Produces-annotated method. com.exampleapp.Hello.presenter.HelloPresenter is injected at com.exampleapp.Hello.MainActivity.HelloPresenter com.exampleapp.Hello.MainActivity is injected at com.exampleapp.di.components.HelloComponent.inject(activity)

public class MainActivity extends AppCompatActivity {

    @Inject
    SharedPreferences mSharedPreferences;

    @Inject
    StoryInterface storyInterface;

    @Inject 
    HelloPresenter helloPresenter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ((BaseApplication) getApplication()).getStoryComponent().inject(this);

        helloPresenter.sayHello();  // This throws an Error

    }

有人能给我指出正确的方向吗？谢谢

Answer 1

在没有看到整个项目的情况下，我的猜测是 Dagger 无法确定如何创建 HelloPresenterImpl 实例，因为您没有提供 StoryView。我想你需要：

@Provides
public StoryView providesStoryView() {
    return new StoryView();
}

如果没有 @Provides- 或 @Produces-annotated 方法，则无法提供 Dagger2

Dagger2 Cannot be provided without an @Provides- or @Produces-annotated method

java

android

dagger-2