Dagger 2多个存储库

Question

所以我是Dagger 2依赖注入的新手。我创建了一个自定义的ViewModelFactory类，它返回我的ViewModel。

@Singleton
public class CustomViewModelFactory implements ViewModelProvider.Factory {
    private final MyCatchesRepository repository;

    @Inject
    public CustomViewModelFactory(MyCatchesRepository repository) {
        this.repository = repository;
    }

    @NonNull
    @Override
    @SuppressWarnings("unchecked")
    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
        if (modelClass.isAssignableFrom(MyCatchViewModel.class)) {
            return (T) new MyCatchViewModel(repository);
        } else {
            throw new IllegalArgumentException("ViewModel Not Found");
        }
    }
}

CustomViewModel在构造函数中使用MyCatchesRepository然后创建MyCatchViewModel。我怎么能改变这个类，以便我可以使用这个ViewModelFactory创建不同的ViewModel与不同的构造函数参数（存储库）

这是创建CustomViewModelFactory的模块

@Module
public class RoomModule {

    private final MyDatabase myDatabase;

    public RoomModule(Application application) {
        this.myDatabase = Room.databaseBuilder(application,
                            MyDatabase.class, AppConstants.DATABASE_NAME)
                            .build();
    }

    @Provides
    @Singleton
    MyCatchesRepository provideCatchesRepository(MyCatchDao myCatchDao) {
        return new MyCatchesRepository(myCatchDao);
    }

    @Provides
    @Singleton
    MyCatchDao providesCatchDao(MyDatabase myDatabase) {
        return myDatabase.myCatchDao();
    }


    @Provides
    @Singleton
    LuresRepository provideLureRepository(LureDao lureDao) {
        return new LuresRepository(lureDao);
    }

    @Provides
    @Singleton
    LureDao provideLureDao(MyDatabase myDatabase) {
        return myDatabase.lureDao();
    }

    @Provides
    @Singleton
    MyDatabase provideDatabase(Application application) {
        return myDatabase;
    }

    @Provides
    @Singleton
    ViewModelProvider.Factory provideCatchesViewModelFactory(MyCatchesRepository catchesRepository) {
        return new CustomViewModelFactory(catchesRepository);
    }
}

ViewModelModule

@Module
public abstract class ViewModelModule {

    @Binds
    @IntoMap
    @ViewModelKey(MyCatchViewModel.class)
    abstract ViewModel myCatchViewModel(MyCatchViewModel myCatchViewModel);

    @Binds
    @IntoMap
    @ViewModelKey(FishingSpotViewModel.class)
    abstract ViewModel fishingSpotViewModel(FishingSpotViewModel fishingSpotViewModel);

    @Binds
    abstract ViewModelProvider.Factory bindCustomViewModelFactory(CustomViewModelFactory customViewModelFactory);

}

Answer 1

Google团队在架构组件示例中提出的方法是使用自定义注释，以便通过dagger提供ViewModel类。

在Java中，Annotation看起来如下。

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import androidx.lifecycle.ViewModel;
import dagger.MapKey;

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

这使用来自Dagger的MapKey，其中任何带注释的ViewModel将组成一个Map，然后可以在ViewModelFactory中使用。

在Google示例中，ViewModelFactory如下所示，使用构造函数注入，您可以访问ViewModel提供程序的映射。

public class ViewModelFactory implements ViewModelProvider.Factory {

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

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

    @NonNull
    @Override
    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
        Provider<ViewModel> viewModelProvider = viewModels.get(modelClass);

        if (viewModelProvider == null) {
            throw new IllegalArgumentException("model class " + modelClass + " not found");
        }

        //noinspection unchecked
        return (T) viewModelProvider.get();
    }
}

在您的示例中，您将最终得到以下内容以提供MyCatchViewModel。然后可以通过遵循相同的模式提供其他ViewModel。

@Module
public abstract class ViewModelModule {
    @Binds
    @IntoMap
    @ViewModelKey(MyCatchViewModel.class)
    abstract ViewModel myCatchViewModel(MyCatchViewModel myCatchViewModel);
}

有关完整示例，您可以查看Google的GithubBrowserSample示例。 https://github.com/googlesamples/android-architecture-components/blob/master/GithubBrowserSample/app/src/main/java/com/android/example/github/di/ViewModelModule.kt