I can not inject repository to ViewModel with dagger 2

Question

I create custom ViewModelProvider.Factory

@Singleton
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;
    }

    @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");
        }

        return (T) viewModelProvider.get();
    }
}

And I create ViewModuleModel class:

@Module
public abstract class ViewModelsModule {

    @Binds
    abstract ViewModelFactory bindViewModelFactory(ViewModelFactory factory);


    @Binds
    @IntoMap
    @ViewModelKey(UsersViewModel.class)
    abstract ViewModel usersViewModel(UsersViewModel UsersViewModel);
}

I create annotation:

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

I add ViewModelModel to Cpmponent:

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

I create ViewModel:

public class UsersViewModel extends ViewModel {

    private final UsersRepository usersRepository;
    private final Router router;

    @Inject
    public UsersViewModel(UsersRepository usersRepository, Router router) {
        this.usersRepository = usersRepository;
        this.router = router;
    }

   ....
}

And I tried inject viewmodel to my fragment:

public class UsersFragment extends BaseFragment {

    private UsersViewModel usersViewModel;

    @Inject
    ViewModelFactory viewModelFactory;
...
usersViewModel = ViewModelProviders.of(this, viewModelFactory).get(UsersViewModel.class);

And I get error:

Caused by: java.lang.InstantiationException: java.lang.Class<viewmodels.UsersViewModel> has no zero argument constructor

when I worked with the presenter, I did just that:

@Singleton
    @Provides
    UsersPresenter provideUsersPresenter(UsersRepository usersRepository, Router router) {
        return new UserPresenter(usersRepository, router);
    }

And pass arguments to constructor. But with ViewModel I not understand how work it?

Naturally, this will not work:

@Binds
    @IntoMap
    @ViewModelKey(UsersViewModel.class)
    abstract ViewModel usersViewModel(UsersViewModel UsersViewModel);

I do not give anything to the constructor anywhere. Then how do I transfer something to the constructor?

Answer 1

One thing I found suspicious is

@Binds abstract ViewModelFactory bindViewModelFactory(ViewModelFactory factory);

idea of @Binds is to bind implementation to interface, you are binding ViewModelFactory to itself, which will lead to dagger compilation error.

Try removing this line and see if that helps.