Injecting ViewModels with an Activity context dependency

I'm using dagger.android and want to inject ViewModels. On the other hand, I have an ApiModule that depends on activity context,

ApiModule

Here is the AppComponent

AppComponent

@Singleton
@Component(modules =
AndroidSupportInjectionModule.class,
AppModule.class,
ActivityBindingModule.class,
ViewModelModule.class
)
public interface AppComponent extends AndroidInjector<MyApp>
@Component.Builder
abstract class Builder extends AndroidInjector.Builder<MyApp>



The ViewModelModule provides ViewModelProvider.Factory

ViewModelModule

@Module
abstract class ViewModelModule
@Binds
abstract ViewModelProvider.Factory bindViewModelFactory(MyAppViewModelFactory factory);



Here is the ActivityBindingModule:

ActivityBindingModule

@Module
abstract class ActivityBindingModule
//MainActivity
@ActivityScoped
@ContributesAndroidInjector(modules =
MainActivityModule.class,
ApiModule.class
)
abstract MainActivity contributeMainActivityInjector();

@Module
abstract class MainActivityModule
@ActivityScoped
@Binds
abstract Activity bindMainActivity(MainActivity activity);

@Binds
@IntoMap
@ViewModelKey(UserViewModel.class)
abstract ViewModel bindUserViewModel(UserViewModel userViewModel);


//SecondActivity
@ActivityScoped
@ContributesAndroidInjector(modules =
SecondActivityModule.class,
ApiModule.class
)
abstract SecondActivity contributeSecondActivityInjector();

@Module
abstract class SecondActivityModule
@ActivityScoped
@Binds
abstract Activity bindSecondActivity(SecondActivity activity);

@Binds
@IntoMap
@ViewModelKey(DetailViewModel.class)
abstract ViewModel bindDetailViewModel(DetailViewModel detailViewModel);




I have these injection hierarchies:

MainActivity --inject--> ViewModelProvider.Factory --inject--> MyAppViewModelFactory --inject--> UserViewModel --inject--> UserRepository --inject--> ApiService --inject--> Activity context

MainActivity --inject--> ViewModelProvider.Factory --inject--> MyAppViewModelFactory --inject--> UserViewModel --inject--> UserRepository --inject--> ApiService --inject--> Activity context

SecondActivity --inject--> ViewModelProvider.Factory --inject--> MyAppViewModelFactory --inject--> DetailViewModel --inject--> DetailRepository --inject--> ApiService --inject--> Activity context

SecondActivity --inject--> ViewModelProvider.Factory --inject--> MyAppViewModelFactory --inject--> DetailViewModel --inject--> DetailRepository --inject--> ApiService --inject--> Activity context

We provide:

Activity

MainActivityModule

SecondActivityModule

ApiService

ApiModule

ActivityBindingModule

UserRepository

DetailRepository

@Singleton

UserViewModel

MainActivityModule

DetailViewModel

SecondActivityModule

MyAppViewModelFactory

Here is MyAppViewModelFactory:

MyAppViewModelFactory

@Singleton
public class MyAppViewModelFactoryimplements ViewModelProvider.Factory
private final Map<Class<? extends ViewModel>, Provider<ViewModel>> creators;

@Inject
MyAppViewModelFactory(Map<Class<? extends ViewModel>, Provider<ViewModel>> creators)
this.creators = creators;


@SuppressWarnings("unchecked")
@Override
@NonNull
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);





I got this error:

error: [Dagger/MissingBinding] [dagger.android.AndroidInjector.inject(T)] java.util.Map<java.lang.Class<? extends android.arch.lifecycle.ViewModel>,javax.inject.Provider<android.arch.lifecycle.ViewModel>> cannot be provided without an @Provides-annotated method.
java.util.Map<java.lang.Class<? extends android.arch.lifecycle.ViewModel>,javax.inject.Provider<android.arch.lifecycle.ViewModel>> is injected at
com.example.viewmodels.MyAppViewModelFactory.<init>(creators)
com.example.viewmodels.MyAppViewModelFactory is injected at
com.example.di.ViewModelModule.bindViewModelFactory(factory)
android.arch.lifecycle.ViewModelProvider.Factory is injected at
com.example.activities.MainActivity.viewModelFactory
com.example.activities.MainActivity is injected at
dagger.android.AndroidInjector.inject(T)
component path: com.example.di.AppComponent ? com.example.di.ActivityBindingModule_ContributeMainActivityInjector.MainActivitySubcomponent


I tried to move bindUserViewModel (from MainActivityModule) and bindDetailViewModel (from SecondActivityModule) to ViewModelModule and I got this error:

bindUserViewModel

MainActivityModule

bindDetailViewModel

SecondActivityModule

ViewModelModule

error: [Dagger/MissingBinding] [dagger.android.AndroidInjector.inject(T)] tk.medlynk.medlynk.http.ApiService cannot be provided without an @Provides-annotated method.
com.example.http.ApiService is injected at
com.example.repositories.UserRepository.<init>(apiService)
com.example.repositories.UserRepository is injected at
com.example.viewmodels.UserViewModel.<init>(userRepo)
com.example.viewmodels.UserViewModel is injected at
com.example.di.ViewModelModule.bindUserViewModel(userViewModel)
java.util.Map<java.lang.Class<? extends android.arch.lifecycle.ViewModel>,javax.inject.Provider<android.arch.lifecycle.ViewModel>> is injected at
com.example.viewmodels.MyAppViewModelFactory.<init>(creators)
com.example.viewmodels.MyAppViewModelFactory is injected at
com.example.di.ViewModelModule.bindViewModelFactory(factory)
android.arch.lifecycle.ViewModelProvider.Factory is injected at
com.example.activities.MainActivity.viewModelFactory
com.example.activities.MainActivity is injected at
dagger.android.AndroidInjector.inject(T)
component path: com.example.di.AppComponent ? com.example.di.ActivityBindingModule_ContributeMainActivityInjector.MainActivitySubcomponent


What am I missing here? the iosched project does the same thing without problem

2 Answers
2

Firstly, you need to restructure your Dagger2 setup in the Application and Activity levels.
Secondly, your ViewModelProviderFactory class is somewhat complicated. I will restructure your code for you now.

ViewModelProviderFactory

Application Level

AppComponent

AppComponent

@Singleton
@Component(modules =
AndroidSupportInjectionModule.class,
AppModule.class,
ActivityBindingModule.class
)
public interface AppComponent extends AndroidInjector<MyApp>
@Component.Builder
abstract class Builder extends AndroidInjector.Builder<MyApp>



ActivityBindingModule

ActivityBindingModule

@Module
abstract class ActivityBindingModule

@ContributesAndroidInjector(modules = MainActivityModule.class)
abstract MainActivity contributeMainActivity();

//This goes for other activities



AppModule This class provides only classes that are common and may be used in
any activity throughout the application.

AppModule

@Module
class AppModule

@Singleton
@Provides
//Your ApiService interface comes here
//Retrofit
//Database



App class should extend DaggerApplication for simplicity. This automatically injects its members

App

class MyApp extends DaggerApplication

@Override
public void onCreate()
super.onCreate();


@Override
protected AndroidInjector<? extends DaggerApplication>
applicationInjector()
return DaggerHorizonMainComponent.builder().create(this);



Activity Level

MainActivityModule This is where you have your ViewModel and ViewModelProviderFactory

MainActivityModule

ViewModel

ViewModelProviderFactory

@Module
class MainACtivityModule

@Provides
MainActivityViewModel provideMainActivityViewModel()
return new MainActivityViewModel();


@Provides
ViewModelProvider.Factory provideViewModelProvider(MainActivityViewModel
viewModel)
return new ViewModelProviderFactory<>(viewModel);


//Your repository comes here too



ViewModel class

ViewModel

class MyViewModel extends ViewModel

@Inject
public MyViewModel()




ViewModelProviderFactory Just copy this code

ViewModelProviderFactory

public class ViewModelProviderFactory<V> implements
ViewModelProvider.Factory
private V viewModel;

public ViewModelProviderFactory(V viewModel)
this.viewModel = viewModel;


@Override
public <T extends ViewModel> T create(Class<T> modelClass)
if (modelClass.isAssignableFrom(viewModel.getClass()))
return (T) viewModel;

throw new IllegalArgumentException("Unknown class name");




Finally, in your MainActivity class, you inject the ViewModelProviderFactory. You don't need to inject Dagger here since you are extending it to DaggerAppCompatActivity

MainActivity

public class Mainactivity extends DaggerAppCompatActivity

@Inject
ViewModelProvider.Factory factory;
private MyViewModel viewModel;

@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
//You set your view here
viewmodel =
ViewModelProviders.of(this,factory).get(MyViewModel.class);





ViewModelProviderFactory

All your setting sounds correct. The main cause is ApiService is not provided.

ApiService

error: [Dagger/MissingBinding]
[dagger.android.AndroidInjector.inject(T)]
tk.medlynk.medlynk.http.ApiService cannot be provided without an
@Provides-annotated method.

To resolve it you just provide it in some module.

class AppModule
@Singleton
@Provides
fun provideApiService(): ApiService
....




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