Cannot create an instance of class - ViewModel

Question

I\'m following an example of google, the example is in java but when I rewrite it in kotlin I can not instantiate the class. I am learning viewmodel. I have a lot o

Answer 1

I had the same issue, in JAVA though. My issue was solved with using the ViewModelFactory as follows:

public class MyViewModelFactory implements ViewModelProvider.Factory {
    private Application mApplication;



    public MyViewModelFactory(Application application) {
        mApplication = application;

    }
    @Override
    public <T extends ViewModel> T create(Class<T> modelClass) {
        return (T) new BookViewModel(mApplication);
    }

And where you call the ViewModel, change it to:

mBookViewModel = new ViewModelProvider(this, new MyViewModelFactory
                (this.getApplication())).get(BookViewModel.class);

You can check this link for this issue from the tutorial's Github issues page: https://github.com/googlecodelabs/android-room-with-a-view/issues

Answer 2

@zunjae

Errors

1 - Syntax code koltin.

2 - Project configuration.

class MainActivity: AppCompatActivity() {
mWordViewModel = ViewModelProviders.of(this@MainActivity).get(WordViewModel(application)::class.java)

...

class WordViewModel constructor (application: Application):  AndroidViewModel(application){

...

class WordRepository constructor(application: Application) {

...

add app build.gradle

apply plugin: 'kotlin-kapt'

kapt "android.arch.lifecycle:extensions:$rootProject.archLifecycleVersion"
kapt "android.arch.persistence.room:compiler:$rootProject.roomVersion"