ListenerForSignleValueEvent and ValueEventListener never firing in Android

Question

So I've been using ValueEventListeners and ListenerForSignleValueEvent throughout my app to pull data from Firebase. From my understanding the onDataChanged() method is supposed to be called right away in each of these and that's been working on all my other pages. For some reason here it's not entering the onDataChanged after being connected to the DatabaseReference nor when I go into Firebase and mess with the data. I know onStart() is working because the onClick for my button is functioning correctly.

public class DocumentsPageFragment extends Fragment {
final DatabaseReference groupsReference = FirebaseDatabase.getInstance().getReferenceFromUrl("https://database.firebaseio.com/groups");

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
    return inflater.inflate(R.layout.document_page,container,false);
}

@Override
public void onStart(){
    super.onStart();

    groupsReference.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            String[] groupNames;
            ArrayList<Group> groupArrayList = new ArrayList<Group>();

            for (DataSnapshot group:dataSnapshot.getChildren()){
                Group currentGroup = group.getValue(Group.class);
                groupArrayList.add(currentGroup);
            }

            if(groupArrayList!= null && groupArrayList.size()<0){
                groupNames = new String[groupArrayList.size()];

                int i = 0;
                for (Group group:groupArrayList){
                    groupNames[i] = group.getName();
                    i++;
                }
            }
            else{
                groupNames = new String[0];
            }

            final ListView groupsListView = (ListView) getActivity().findViewById(R.id.documents_groups_listview);

            ArrayAdapter<String> groupListArrayAdapter =
                    new ArrayAdapter<String>(getActivity(),android.R.layout.simple_list_item_1,groupNames);
            groupsListView.setAdapter(groupListArrayAdapter);

            AdapterView.OnItemClickListener groupListViewClickListener =
                    new AdapterView.OnItemClickListener() {
                        @Override
                        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                            openSelectedGroupsDocuments(groupsListView.getItemAtPosition(position).toString());
                        }
                    };

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    Button uploadButton = (Button) getActivity().findViewById(R.id.documents_upload_doc_button);

    uploadButton.setOnClickListener(new Button.OnClickListener(){
        public void onClick(View view){
            DocumentUploadFragment fragment = new DocumentUploadFragment();
            FragmentManager fragmentManager = getFragmentManager();
            fragmentManager.beginTransaction().replace(R.id.flContent,fragment).commit();
        }
    });

}

Please add error handling in `onCancelled`. See http://stackoverflow.com/documentation/firebase/5548/how-do-i-listen-for-errors-when-accessing-the-database/22652/detect-errors-when-reading-data-on-android#t=201704302013247215931 — Frank van Puffelen, Apr 30 '17 at 20:13
Thanks for your response. Will that output an error to the android monitor? Sorry, I'm still learning the ropes on this. — T. Mitchell, May 01 '17 at 18:42
After debugging more closely, it's not hitting that either. It runs the first line setting the event handler and then drops down to closing the eventhandler class without ever stepping into it and running either onDataChanged or onCancelled. — T. Mitchell, May 01 '17 at 19:25
Set breakpoints *inside* `onDataChange()` and `onCancelled()`. They run asynchronously, not when you expected. See http://stackoverflow.com/questions/33203379/setting-singleton-property-value-in-firebase-listener — Frank van Puffelen, May 01 '17 at 21:03

ListenerForSignleValueEvent and ValueEventListener never firing in Android

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