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I am using dagger2 library. whenever I am trying to run my project is says not able to create instance of view model class.
main activity where I am trying to create an instance
((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 log
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
Instead of:
mViewModel = ViewModelProviders.of(this).get(MoviesDataViewModel.class);
Perform:
mViewModel = ViewModelProviders.of(this, viewModelFactory).get(MoviesDataViewModel.class);
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