java - 继承和泛型以及 Dagger2

Question

我有两种 fragment 。其中之一是 ListFragment，另一个是 ListWithFilterFragment，ListWithFilterFragment 扩展了 ListFragment。另外，我还有两个用于这些 fragment 的演示者，ListWithFilterPresenter 扩展了 ListPresenter。所以我在 Dagger 中为演示者和单独的组件定义了单独的模块。我想向这些 fragment 注入(inject)正确的演示者，但出现错误

这是ListFragment:

public class ListFragment<V extends ListView> extends BaseFragment<V, ListPresenter<V>> implements ListView {
    @Inject
    ListPresenter presenter;

    @NonNull
    @Override
    public ListPresenter createPresenter() {
    DaggerListComponent.builder().build().inject((ListFragment<ListView>) this);
    return presenter;
}

这是ListWithFilterFragment:

public class ListWithFilterFragment extends ListFragment<ListWithFilterView> implements ListWithFilterView {
    @Inject
    ListWithFilterPresenter presenter;

    @NonNull
    @Override
    public ListWithFilterPresenter createPresenter() {
        DaggerListWithFilterComponent.builder().build().inject(this);
        return presenter;
    }
}

这是ListComponent:

@Singleton
@Component(modules = {ListPresenterModule.class, 
ListInteractorModule.class})
public interface ListComponent {
    void inject(ListFragment<ListView> fragment);
}

这是ListWithFilterComponent:

@Singleton
@Component(modules = {ListWithFilterPresenterModule.class, 
ListInteractorModule.class})
public interface ListWithFilterComponent {
    void inject(ListWithFilterFragment fragment);
}

和我的演示者模块

@Module
public class ListWithFilterPresenterModule {
    @Provides @NonNull @Singleton
    public ListWithFilterPresenter providePresenter(ListInteractor interactor) {
        return new ListWithFilterPresenter(interactor);
    }
} 

@Module
public class ListPresenterModule {
    @Provides @NonNull @Singleton
    public ListPresenter providePresenter(ListInteractor interactor) {
        return new ListPresenter(interactor);
    }
}

Error:(16, 10) error: com.sober.appModules.List.presenter.ListPresenter cannot be provided without an @Provides- or @Produces-annotated.method.com.sober.appModules.List.presenter.ListPresenter is injected at com.sober.appModules.List.ui.ListFragment.presenter com.sober.appModules.List.ui.ListWithFilterFragment is injected at com.sober.appModules.List.injection.ListWithFilterComponent.inject(fragment)

Answer 1

Dagger 不进行部分注入(inject)。它要么可以提供所有对象，要么会失败并显示无法提供。

在您的情况下，ListWithFilterComponent 无法向 ListWithFilterFragment 或其 ListFragment 父级提供 ListPresenter。

查看行尾的注释

error: List.presenter.ListPresenter cannot be provided without an @Provides- or @Produces-annotated.method.
List.presenter.ListPresenter is injected at  <- missing object
List.ui.ListFragment.presenter <- field in parent that is getting injected
List.ui.ListWithFilterFragment is injected at <- object it tries to inject
List.injection.ListWithFilterComponent.inject(fragment) <- component that's missing something

如果您想保留当前设置，您还需要从 ListWithFilterComponent 提供 ListPresenter，否则您将需要重构您的 fragment ，以便它们不不要互相扩展。