I am having issues injecting a dependency into my viewModel. I keep getting Cannot create an instance of class ....viewModel.UserProfileViewModel. I have been trying to figure out this issue. Any suggestions would be really appreciated. Here is my code. I have seen in other questions that this is usually caused by having a parameter in the constructor of the viewmodel, and creating a factory should resolve the issue. but it did not seem to work quite as well for me. I must be missing something.
Thanks!
App component:
@Singleton
@Component(modules = {AndroidSupportInjectionModule.class, ViewModelModule.class})
public interface ApplicationComponent {
@Component.Builder
interface Builder {
@BindsInstance Builder application(Application application);
ApplicationComponent build();
}
}
=====================================================
App module:
@Module
public class AppModule {
Application mApplication;
public AppModule(Application application){
mApplication = application;
}
@Provides
@Singleton
Application providesApplication(){
return mApplication;
}
}
===========================================================
ViewFactory
@Singleton
public class ViewModelFactory implements ViewModelProvider.Factory {
private final Map<Class<? extends ViewModel>, Provider<ViewModel>> creators;
@Inject
public ViewModelFactory(Map<Class<? extends ViewModel>, Provider<ViewModel>> viewModels) {
this.creators = viewModels;
}
@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);
}
}
}
===========================================================
View key
@Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@MapKey
@interface ViewModelKey {
Class<? extends ViewModel> value();
}
========================================================
View Module
@Module
public abstract class ViewModelModule {
@Binds
@IntoMap
@ViewModelKey(UserProfileViewModel.class)
abstract ViewModel bindUserViewModel(UserProfileViewModel userViewModel);
}
===========================================================
view model class
public class UserProfileViewModel extends ViewModel {
private UserRepository mUserRepository;
private LiveData<User> mObservableUser;
@Inject
public UserProfileViewModel(@NonNull UserRepository userRepo){
this.mUserRepository = userRepo;
}
public void init(String userId){
if (this.mObservableUser != null) {
return;
}
mObservableUser = mUserRepository.getUser(userId);
}
public LiveData<User> getUser() {
return this.mObservableUser;
}
}
====================================================
in fragment
viewModel = ViewModelProviders.of(this, viewModelFactory).get(UserProfileViewModel.class);
viewModel.init(mUserId);
Stack trace 22:08:49.677 19211-19211/nonso.android.nonso E/AndroidRuntime: FATAL EXCEPTION: main Process: nonso.android.nonso, PID: 19211 java.lang.RuntimeException: Cannot create an instance of class nonso.android.nonso.viewModel.UserProfileViewModel at android.arch.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:153) at android.arch.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:210) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102) at nonso.android.nonso.ui.fragments.ProfileFragment.setUp(ProfileFragment.java:133) at nonso.android.nonso.ui.fragments.ProfileFragment.onActivityCreated(ProfileFragment.java:122) at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:2355) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1451) at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1827) at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797) at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596) at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383) at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2245) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:703) at android.os.Handler.handleCallback(Handler.java:790) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6494) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) Caused by: java.lang.InstantiationException: java.lang.Class has no zero argument constructor at java.lang.Class.newInstance(Native Method) at android.arch.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:151) at android.arch.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:210) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102) at nonso.android.nonso.ui.fragments.ProfileFragment.setUp(ProfileFragment.java:133) at nonso.android.nonso.ui.fragments.ProfileFragment.onActivityCreated(ProfileFragment.java:122) at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:2355) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1451) at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1759) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1827) at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:797) at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2596) at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2383) at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2338) at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2245) at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:703) at android.os.Handler.handleCallback(Handler.java:790) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6494) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)