java - 无法使用 dagger2 android java 注入(inject) ViewModel

Question

我正在尝试借助 dagger2 中常见的 ViewModelProviderFactory 注入(inject) viewmodel。 (这是我的第一个带有 Dagger 和架构组件的应用程序)这是我在构建代码时遇到的错误。

Error:(26, 10) error: java.util.Map,javax.inject.Provider> cannot be provided without an @Provides-annotated method.

这是我使用的代码

ViewModelProviderFactory

@PerActivity

public class ViewModelProviderFactory implements ViewModelProvider.Factory {

    private final Map<Class<? extends ViewModel>, Provider<ViewModel>> creators;

    @Inject
    public ViewModelProviderFactory(Map<Class<? extends ViewModel>, Provider<ViewModel>> creators) {
        this.creators = creators;
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T extends ViewModel> T create(Class<T> modelClass) {
        Provider<? extends ViewModel> creator = creators.get(modelClass);
        if (creator == null) {
            for (Map.Entry<Class<? extends ViewModel>, Provider<ViewModel>> entry : creators.entrySet()) {
                if (modelClass.isAssignableFrom(entry.getKey())) {
                    creator = entry.getValue();
                    break;
                }
            }
        }
        if (creator == null) {
            throw new IllegalArgumentException("unknown model class " + modelClass);
        }
        try {
            return (T) creator.get();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

ViewModelModule

@Module
public abstract class ViewModelModule {
    @Binds
    @IntoMap
    @ViewModelKey(HomeViewModel.class)
    abstract ViewModel bindHomeViewModel(HomeViewModel homeViewModel);

    @Binds
    abstract ViewModelProvider.Factory bindViewModelFactory(ViewModelProviderFactory factory);
}

应用组件

@Singleton
@Component(modules = {ApplicationModule.class, ViewModelModule.class})
public interface ApplicationComponent {

    void inject(BaseApp app);

    @ApplicationContext
    Context getContext();

    Application getApplication();

    WebService getWebService();

    PreferencesHandler getPreferencesHandler();

    InternetUtils getInternetUtils();
}

Activity 组件

@PerActivity
@Component(dependencies = ApplicationComponent.class, modules = ActivityModule.class)
public interface ActivityComponent {

    void inject(MainActivity mainActivity);

    void inject(SampleListActivity sampleListActivity);

    void inject(HomeActivity homeActivity);
}

ViewModelKey

@Documented
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@MapKey
public @interface ViewModelKey {
    Class<? extends ViewModel> value();
}

在我的 Activity 中我使用这段代码

@Inject
ViewModelProviderFactory mViewModelFactory;
........
oncreate(){
...
homeViewModel = ViewModelProviders.of(this,mViewModelFactory).get(HomeViewModel.class);
.......
}

Answer 1

你的 ActivityComponent是 Component (不是子组件)依赖于 ApplicationComponent , 因此它无法访问在 AppComponent 中设置的 map 。

要么切换到使用 SubComponent为你的ActivityComponent ，或确保包含 Map<Class<? extends ViewModel>, Provider<ViewModel>> 的提供方法在您的 AppComponent 中，以便依赖组件可以访问它。

interface AppComponent {
  // ..
  Map<Class<? extends ViewModel>, Provider<ViewModel>> creators();
}