Blank screen when trying to implement MVVM / ViewModel and data binding architecture - android-fragments

Question

I am trying to implement the Model-View-ViewModel architectural pattern and XML data binding in my Android Java app. The code seems all correct as far as I can see, however I'm getting a blank screen when I run the app (not even the bottomNavigationView is showing). I am using a ViewModel to store/persist data for a fragment called AllTimeBestFragment. Specifically, AllTimeBestFragment is one of three fragments in a Viewpager-tabLayout.
Would appreciated any insight into what I'm doing wrong!
AllTimeBestFragment
public class AllTimeBestFragment extends Fragment {
private ImageViewCallback imageViewCallback;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(Constants.SkiCompanionDebug, "AllTimeBestFragment");
bindToViewModel();
return inflater.inflate(R.layout.fragment_all_time_best, container, false);
}
//imageview callback
#Override
public void setUserVisibleHint(boolean visible) {
super.setUserVisibleHint(visible);
imageViewCallback.setImage(R.drawable.all_time_best);
}
public void addCallback(ImageViewCallback imageViewCallback) {
this.imageViewCallback = imageViewCallback;
}
//binding the view (fragment) to the asoociated viewModel
public void bindToViewModel(){
FragmentAllTimeBestBinding binding = DataBindingUtil.setContentView(getActivity(), R.layout.fragment_all_time_best);
AllTimeBestViewModel viewModel = ViewModelProviders.of(this).get(AllTimeBestViewModel.class);
AllTimeStats allTimeStats = BCCDatabase.getInstance(getActivity()).getAllTimeStats();
viewModel.init(allTimeStats);
binding.setAllTimeBestViewModel(viewModel);
}
}
AllTimeBestViewModel
public class AllTimeBestViewModel extends ViewModel {
private AllTimeStats allTimeStats;
public void init(AllTimeStats allTimeStats) {
this.allTimeStats = allTimeStats;
}
public String getDurationTotal(){
return ""+allTimeStats.getDurationTotal();
}
}
fragment_all_time_best.xml
<data>
<variable
name="allTimeBestViewModel"
type="skicompanion.skicompanion.viewmodels.AllTimeBestViewModel" />
</data>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/track_scrollview"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
tools:context="skicompanion.skicompanion.fragments.AllTimeBestFragment">
<android.support.v7.widget.CardView
android:id="#+id/duration_cardview"
android:layout_width="match_parent"
android:layout_height="180dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/duration_total"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{allTimeBestViewModel.durationTotal}"
android:textSize="18sp"
android:textStyle="bold"
app:layout_constraintEnd_toEndOf="#+id/duration_total_tv"
app:layout_constraintStart_toStartOf="#+id/imageView2"
app:layout_constraintTop_toBottomOf="#+id/duration_total_tv" />
...
...
...
Gradle
implementation "android.arch.lifecycle:extensions:1.1.1"
implementation "android.arch.lifecycle:viewmodel:1.1.1"

Answer 1

I found the answer here: How to use data-binding with Fragment
I was binding the data as if I were dealing with an activity - I needed to bind it for a fragment instead. The trick was to use DataBindingUtil.inflate rather than DataBindingUtil.setContentView. Below is the correct code snippet:
public class AllTimeBestFragment extends Fragment {
private ImageViewCallback imageViewCallback;
private FragmentAllTimeBestBinding binding;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(Constants.SkiCompanionDebug, "AllTimeBestFragment");
binding = DataBindingUtil.inflate(inflater, R.layout.fragment_all_time_best, container, false);
bindToViewModel();
return binding.getRoot();
}
//imageview callback
#Override
public void setUserVisibleHint(boolean visible) {
super.setUserVisibleHint(visible);
imageViewCallback.setImage(R.drawable.all_time_best);
}
public void addCallback(ImageViewCallback imageViewCallback) {
this.imageViewCallback = imageViewCallback;
}
//binding the view (fragment) to the asoociated viewModel
public void bindToViewModel(){
AllTimeBestViewModel viewModel = ViewModelProviders.of(this).get(AllTimeBestViewModel.class);
AllTimeStats allTimeStats = BCCDatabase.getInstance(getActivity()).getAllTimeStats();
viewModel.init(allTimeStats);
binding.setAllTimeBestViewModel(viewModel);
}
}