Unable to instantiate custom ViewModel

Question

I am using the dagger2 library. whenever I try to run my project, it says that it cannot create an instance of the view model class.

The main activity where I try to instantiate

((MovieApplication) getApplication()).getAppComponent().inject(this); mViewModel = ViewModelProviders.of(this).get(MoviesDataViewModel.class); 

My factory class

 public class ViewModelFactory implements ViewModelProvider.Factory { private MoviesDataViewModel mViewModel; @Inject public ViewModelFactory(MoviesDataViewModel viewModel) { this.mViewModel = viewModel; } @Override public <T extends ViewModel> T create(Class<T> modelClass) { if (modelClass.isAssignableFrom(MoviesDataViewModel.class)) { return (T) mViewModel; } throw new IllegalArgumentException("Unknown class name"); } 

My magazine

  Caused by: java.lang.RuntimeException: Cannot create an instance of class com.moviedata.viewmodel.MoviesDataViewModel at android.arch.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:145) at android.arch.lifecycle.ViewModelProviders$DefaultFactory.create(ViewModelProviders.java:143) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:128) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:96) at com.moviedata.ui.MainActivity.onCreate(MainActivity.java:28) at android.app.Activity.performCreate(Activity.java:6321) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2426) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2535) at android.app.ActivityThread.access$1100(ActivityThread.java:154) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1396) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5582) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.InstantiationException: java.lang.Class<com.moviedata.viewmodel.MoviesDataViewModel> has no zero argument constructor at java.lang.Class.newInstance(Native Method) 

Answer 1

Instead:

 mViewModel = ViewModelProviders.of(this).get(MoviesDataViewModel.class); 

Run:

 mViewModel = ViewModelProviders.of(this, viewModelFactory).get(MoviesDataViewModel.class); 

Answer 2

The solution for me was to introduce activity because I used Dagger2

  AndroidInjection.inject(this); 

Answer 3

You must add the code below in all actions if you use multiple actions

 AndroidInjection.inject(this); 

Answer 4

Replace:

 private MoviesDataViewModel mViewModel; 

with:

 MoviesDataViewModel mViewModel;