Architectural Components: Realm in ViewModel (based on https://github.com/googlesamples/android-architecture-components/blob/178fe541643adb122d2a8925cf61a21950a4611c/BasicSample/app/src/main/java/com/example/android/persistence/viewmodel/ProductListViewModel.java )

arch-comps-4.java

// based on  https://github.com/googlesamples/android-architecture-components/blob/178fe541643adb122d2a8925cf61a21950a4611c/BasicSample/app/src/main/java/com/example/android/persistence/viewmodel/ProductListViewModel.java
public class ProductListViewModel {
    private final MutableLiveData<List<ProductEntity>> observableProducts = new MutableLiveData<>();
  
    Realm realm;
    RealmResults<ProductEntity> results;
    RealmChangeListener<RealmResults<ProductEntity>> realmChangeListener = (results) -> {
        if(results.isLoaded() && results.isValid()) { 
            observableProducts.setValue(results);
        }
    };
  
    public ProductListViewModel() {
        realm = Realm.getDefaultInstance(); 
        // previously: final DatabaseCreator databaseCreator = 
        //                       DatabaseCreator.getInstance(this.getApplication());
        
        observableProducts.setValue(null); // if using async query API, the change listener will set the loaded results.
        
        results = realm.where(ProductEntity.class).findAllSortedAsync("id");  // this could be from dao instead
        results.addChangeListener(realmChangeListener);
    }
  
    public LiveData<List<ProductEntity>> getProducts() {
        return observableProducts;
    }
  
    @Override
    protected void onCleared() {
        results.removeChangeListener(realmChangeListener);
        realm.close();
        realm = null;
    }
}