如何使用 Dagger2 @Inject AndroidViewModel？

Question

我目前正在研究 Dagger2 在我的 Android 应用程序中的使用。

implementation 'com.google.dagger:dagger:2.21'
annotationProcessor 'com.google.dagger:dagger-compiler:2.21'

implementation 'com.google.dagger:dagger-android:2.21'
implementation 'com.google.dagger:dagger-android-support:2.21'
annotationProcessor 'com.google.dagger:dagger-android-processor:2.21'

我已经设法 @Inject ViewModels 及其关联的存储库

使用以下代码：-

import java.util.Map;

import javax.inject.Inject;
import javax.inject.Provider;
import javax.inject.Singleton;

import androidx.lifecycle.ViewModel;
import androidx.lifecycle.ViewModelProvider;

@Singleton
public class DaggerViewModelFactory implements ViewModelProvider.Factory {

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

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

    @SuppressWarnings("unchecked")
    @Override
    public <T extends ViewModel> T create(final 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 (final Exception e) {
            throw new RuntimeException(e);
        }
    }
}

import androidx.lifecycle.ViewModel;
import androidx.lifecycle.ViewModelProvider;
import dagger.Binds;
import dagger.Module;
import dagger.multibindings.IntoMap;

@Module
public abstract class ViewModelModule {

    @Binds
    abstract ViewModelProvider.Factory bindViewModelFactory(final DaggerViewModelFactory factory);

    @Binds
    @IntoMap
    @ViewModelKey(StilettoViewModel.class)
    abstract ViewModel provideStilettoViewModel(final StilettoViewModel stilettoViewModel);
}

但是我的一些 ViewModel 是 androidx.lifecycle.AndroidViewModel。

我创建了这个 ViewModelFactory:-

import android.app.Application;

import java.util.Map;

import javax.inject.Provider;
import javax.inject.Singleton;

import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.ViewModel;
import androidx.lifecycle.ViewModelProvider;

@Singleton
public class DaggerAndroidViewModelFactory extends ViewModelProvider.AndroidViewModelFactory {

    private final Application application;

    private Map<Class<? extends AndroidViewModel>, Provider<AndroidViewModel>> creators;


    /**
     * Creates a {@code AndroidViewModelFactory}
     *
     * @param application an application to pass in {@link AndroidViewModel}
     */
    public DaggerAndroidViewModelFactory(@NonNull final Application application) {
        super(application);
        this.application = application;
    }


    @NonNull
    @Override
    public <T extends ViewModel> T create(@NonNull final Class<T> modelClass) {
        return super.create(modelClass);
    }
}

和这个 Dagger 模块

import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.ViewModelProvider;
import dagger.Binds;
import dagger.Module;
import dagger.multibindings.IntoMap;

@Module
public abstract class ViewModelModule {

    @Binds
    abstract ViewModelProvider.AndroidViewModelFactory bindAndroidViewModelFactory(final DaggerAndroidViewModelFactory factory);

    @Binds
    @IntoMap
    @ViewModelKey(MyAndroidViewModel.class)
    abstract AndroidViewModel provideArticlesViewModel(final ArticlesViewModel articlesViewModel);
}

此代码将无法构建，因为我收到此错误

error: [Dagger/MissingBinding] MyAndroidViewModel cannot be provided without an @Inject constructor or an @Provides-annotated method.

是否可以用 Dagger2 注入 androidx.lifecycle.AndroidViewModel？

我的实施哪里出了问题？

Answer 1

如果你有 @Module @Provides 和 Application（或者你使用 @BindsInstance + @Component.Builder，老实说两者都有效）：

@Module
public class AppModule {
    private final Application app;

    public AppModule(Application app) {
        this.app = app;
    }

    @Provides
    Application app() { return app; } 
}

和

@Component(modules={AppModule.class, ...})
@Singleton
public interface AppComponent {
}

然后现在不再使用 AndroidViewModel：

public class MyViewModel extends AndroidViewModel {
    public MyViewModel(Application app) {
        ...
    }
}

您可以将常规 ViewModel 与 @Inject 构造函数一起使用：

public class MyViewModel extends ViewModel {
    @Inject
    MyViewModel(Application app) {
        ...
    }
}

并且您可以通过 DaggerViewModelFactory.

像使用任何其他常规 ViewModel class 一样使用它

Answer 2

使用 Hilt 注入 ViewModel 对象。 阅读更多关于 here

将构造函数注释为 ViewModelInject 提供视图模型工厂

@AndroidEntryPoint
class HomeFragment : Fragment() {

    private val homeViewModel: HomeViewModel by viewModels()
}

而视图模型 class 是：

class HomeViewModel @ViewModelInject constructor(
    authorizationRepository: AuthorizationRepository
) : ViewModel()

将以下附加依赖项添加到您的 Gradle 文件

implementation 'androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha02'
kapt 'androidx.hilt:hilt-compiler:1.0.0-alpha02'

如何使用 Dagger2 @Inject AndroidViewModel？

How to @Inject AndroidViewModel with Dagger2?

android

dagger-2

android-viewmodel