2019-02-18 16:17:27.584 10742-10742/avocado.droid.room E/AndroidRuntime: FATAL EXCEPTION: main
Process: avocado.droid.room, PID: 10742
java.lang.RuntimeException: Unable to start activity ComponentInfo{avocado.droid.room/avocado.droid.room.ui.MainActivity}: java.lang.RuntimeException: Cannot create an instance of class avocado.droid.room.viewmodel.ProductListViewModel
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3303)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3411)
    at android.app.ActivityThread.-wrap12(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1994)
    at android.os.Handler.dispatchMessage(Handler.java:108)
    at android.os.Looper.loop(Looper.java:166)
    at android.app.ActivityThread.main(ActivityThread.java:7529)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)
 Caused by: java.lang.RuntimeException: Cannot create an instance of class avocado.droid.room.viewmodel.ProductListViewModel
    at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:252)
    at androidx.lifecycle.ViewModelProvider$FactoryWrapper.create(ViewModelProvider.java:268)
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:179)
    at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:147)
    at avocado.droid.room.ui.ProductListFragment.onActivityCreated(ProductListFragment.java:49)

public class ProductListViewModel extends AndroidViewModel {

    private final DataRepository mRepository;
    private final MediatorLiveData<List<ProductEntity>> mObservableProducts;

    public ProductListViewModel(Application application) {
        super(application);

        mObservableProducts = new MediatorLiveData<>();

        mObservableProducts.setValue(null);
        mRepository = ((BasicApp) application).getRepository();
        LiveData<List<ProductEntity>> products = mRepository.getProducts();

        mObservableProducts.addSource(products, mObservableProducts::setValue);
    }

    /**
     * Expose the LiveData Products query so the UI can observe it.
     */
    public LiveData<List<ProductEntity>> getProducts() {
        return mObservableProducts;
    }

    public LiveData<List<ProductEntity>> searchProducts(String query) {
        return mRepository.searchProducts(query);
    }
}

public class ProductListFragment extends Fragment {

public static final String TAG = "ProductListFragment";

private ProductAdapter mProductAdapter;

private ListFragmentBinding mBinding;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                         @Nullable Bundle savedInstanceState) {
    mBinding = DataBindingUtil.inflate(inflater, R.layout.list_fragment, container, false);

    mProductAdapter = new ProductAdapter(mProductClickCallback);
    mBinding.productsList.setAdapter(mProductAdapter);

    return mBinding.getRoot();
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    final ProductListViewModel viewModel =
            ViewModelProviders.of(this).get(ProductListViewModel.class);

    mBinding.productsSearchBtn.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Editable query = mBinding.productsSearchBox.getText();
            if (query == null || query.toString().isEmpty()) {
                subscribeUi(viewModel.getProducts());
            } else {
                subscribeUi(viewModel.searchProducts("*" + query + "*"));
            }
        }
    });

    subscribeUi(viewModel.getProducts());
}