Recycler view lost after fragment replacement - android-recyclerview

Question

I have a single activity which replaces a fragment containing a recycler view with a fragment containing details of the selected viewholder item. When the back button is pressed the fragment containing the recycler view is restored but the recycler view items are no longer displayed. However, views are restored upon device rotation. All model data is stored in a SQLite database and the adapter list is updated on resume of its fragment .
CrimeListFragment.Java
public class CrimeListFragment extends Fragment {
private Callbacks callbacks;
public interface Callbacks {
public void onItemSelected(UUID id);
}
#Override
public void onAttach(#NonNull Context context) {
super.onAttach(context);
callbacks = (Callbacks) context;
}
#Override
public void onDetach() {
super.onDetach();
callbacks = null;
}
private RecyclerView crimeListRecycler;
private CrimeListAdapter adapter;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_crime_list, container, false);
crimeListRecycler = view.findViewById(R.id.crime_list);
crimeListRecycler.setLayoutManager(new LinearLayoutManager(getActivity()));
updateUI();
return view;
}
#Override
public void onResume() {
super.onResume();
updateUI();
}
#Override
public void onCreateOptionsMenu(#NonNull Menu menu, #NonNull MenuInflater inflater) {
super.onCreateOptionsMenu(menu, inflater);
inflater.inflate(R.menu.fragment_crime_list, menu);
MenuItem showSubtitle = menu.findItem(R.id.show_subtitle);
}
#Override
public boolean onOptionsItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.new_crime:
Crime crime = new Crime();
CrimeLab.get(getActivity()).addCrime(crime);
/*Intent intent = CrimeActivity.createIntent(getActivity(), crime.getId());
startActivity(intent);*/
callbacks.onItemSelected(crime.getId());
return true;
default:
return onOptionsItemSelected(item);
}
}
private void updateUI() {
List<Crime> crimes = CrimeLab.get(getActivity()).getCrimes();
if (adapter == null) {
adapter = new CrimeListAdapter(crimes);
crimeListRecycler.setAdapter(adapter);
} else {
adapter.setCrimesList(crimes);
adapter.notifyDataSetChanged();
}
}
public class CrimeListAdapter extends RecyclerView.Adapter<CrimeListAdapter.CrimeHolder> {
private List<Crime> crimeList;
public CrimeListAdapter(List<Crime> crimes) {
crimeList = crimes;
}
#NonNull
#Override
public CrimeHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(getActivity()).inflate(R.layout.list_item_crime, parent, false);
return new CrimeHolder(view);
}
#Override
public void onBindViewHolder(#NonNull CrimeHolder holder, int position) {
Crime crime = crimeList.get(position);
holder.bind(crime);
}
#Override
public int getItemCount() {
return crimeList.size();
}
public void setCrimesList(List<Crime> crimes) {
crimeList = crimes;
}
public class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
private Crime crime;
private TextView crimeTitleTextView;
private TextView crimeDateTextView;
public CrimeHolder(#NonNull View itemView) {
super(itemView);
crimeTitleTextView = itemView.findViewById(R.id.crime_title);
crimeDateTextView = itemView.findViewById(R.id.crime_date);
itemView.setOnClickListener(this);
}
public void bind(Crime crime) {
this.crime = crime;
crimeTitleTextView.setText(crime.getTitle());
crimeDateTextView.setText(crime.getDate().toString());
}
#Override
public void onClick(View v) {
callbacks.onItemSelected(crime.getId());
/*Intent intent = CrimeActivity.createIntent(getActivity(), crime.getId());
startActivity(intent);*/
}
}
}
}
MasterActivity
public class MasterActivity extends AppCompatActivity implements CrimeListFragment.Callbacks {
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fragment);
FragmentManager fm = getSupportFragmentManager();
Fragment fragment = fm.findFragmentById(R.id.fragment_container);
if (fragment == null) {
fragment = new CrimeListFragment();
fm.beginTransaction()
.add(R.id.fragment_container, fragment)
.commit();
}
}
#Override
public void onItemSelected(UUID id) {
Fragment fragment = CrimeFragment.newInstance(id);
FragmentManager fm = getSupportFragmentManager();
fm.beginTransaction()
.replace(R.id.fragment_container, fragment)
.addToBackStack(null)
.commit();
}
}

Answer 1

Please share your code. Something to check when you replace/add your fragment on top of recyclerview fragment.