Dagger2 viewmodel mapping.

AppComponent.java

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

    void inject(Application app);

    @Component.Builder
    interface Builder {

        @BindsInstance
        Builder application(Application app);

        AppComponent build();
    }
}

AppModule.java

@Module(includes = {AndroidInjectionModule.class, ViewModelModule.class})
public class AppModule {

    @Provides
    Context provideContext(Application application) {
        return application.getApplicationContext();
    }
    
    @Provides
    android.app.Application provideAndroidApplication(Application application) {
        return application;
    }
}

AppViewModelFactory.java

@Singleton
public class SampleViewModelFactory extends ViewModelProvider.NewInstanceFactory {

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

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

    @NonNull
    @SuppressWarnings("unchecked")
    @Override
    public <T extends ViewModel> T create(@NonNull 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);
        }
    }
}

BuildersModule.java

@Module
abstract class BuildersModule {
  
    @ContributesAndroidInjector(modules = {SampleActivityModule.class})
    abstract SampleActivity bindSampleActivity();
  
}

SampleActivity.java

public class SampleActivity extends AppCompatActivity {
    
    @Inject
    SampleViewModelFactory viewModelFactory;
  
    private SampleViewModel viewModel;
  
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        AndroidInjection.inject(this);
        super.onCreate(savedInstanceState);

        viewModel = ViewModelProviders.of(this, viewModelFactory).get(SampleViewModel.class);
    }
}

SampleActivityModule.java

@Module(includes = {InterviewModule.class})
public class SampleActivityModule {

}

SampleViewModel.java

public class SampleViewModel extends AndroidViewModel {

    @Inject
    public InterviewViewModel(@NonNull final Application application) {
        super(application);
      
    }
}

ViewModelKey.java

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

ViewModelModule.java

@Module
public abstract class ViewModelModule {

    @Binds
    @IntoMap
    @ViewModelKey(SampleViewModel.class)
    abstract ViewModel bindSampleViewModel(SampleViewModel viewModel);

    @Binds
    abstract ViewModelProvider.Factory bindViewModelFactory(AppViewModelFactory factory);

}