RecyclerView with FirebaseRecyclerAdapter remains empty

Question

I'm currently trying to build an app using Firebase Realtime Database, I already have some data there, which are structured like this (excerpt of the exported JSON)

{
"userdata" : {
    "593QfAvxxxxxxxxxxxHqCMA3" : {
      "calcentries" : {
        "-LJy_hvvm3ySUqM6sQcf" : {
          "candyCount" : 0,
          "evolutionLine" : {
            "candyNeeded" : 25,
            "evolvedSpecies" : 2,
            "precondition" : {
              "buddyKm" : 0,
              "preconditionType" : "NONE"
            }
          },
          "evolvedSpeciesTransferCount" : 0,
          "newPokedexEntry" : false,
          "pokemonCount" : 0,
          "possibleEvoCountWithPreconditionsMet" : 0,
          "possibleEvolutionCount" : 0,
          "preconditionsMet" : false,
          "sourceSpecies" : 1,
          "sourceSpeciesCountAfterEvolutions" : 0,
          "sourceSpeciesTransferCount" : 0
        },
        "-LJy_hwMVTM20f0c5JOJ" : { ...

}

I try to display them in a RecyclerView by using a FirebaseRecyclerAdapter (Firebase UI 4.1.0). This is how I initialize the RecyclerView and the adapter in the onCreate of my activity

mRecyclerView = findViewById(R.id.rv_calculation_input);

RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this,1, LinearLayoutManager.VERTICAL,false);

mRecyclerView.setLayoutManager(layoutManager);
mRecyclerView.setHasFixedSize(true);

FirebaseRecyclerOptions<CalculationInputEntry> opt
     = new FirebaseRecyclerOptions.Builder<CalculationInputEntry>()
         .setLifecycleOwner(this)
         .setQuery(AppUtil.getCurrentUserRef().child("calcentries"), CalculationInputEntry.class)
         .build();

mAdapter = new FirebaseRecyclerAdapter<CalculationInputEntry, CalculationInputEntryViewHolder>(opt) {        
     @NonNull
     @Override
     public CalculationInputEntryViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
          View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_main, parent, false);
          return new CalculationInputEntryViewHolder(v);
     }

     @Override
     protected void onBindViewHolder(@NonNull CalculationInputEntryViewHolder holder, int position, @NonNull CalculationInputEntry model) {
           holder.bindEntry(model);
     }
 };

mRecyclerView.setAdapter(mAdapter);

The view remains empty... By setting the lifecycle owner, manually calling startListening and stopListening on the adapter should not be necessary, right?

I set the Firebase log level to debug and found quite some entries that "CHILD_ADDED" events are raised, even showing the expected data...

D/EventRaiser: Raising /userdata/593QxxxxxxxxxCMA3/calcentries: CHILD_ADDED: { -LJy_tNakAl19tH5H_tb: {preconditionsMet=false, sourceSpeciesCountAfterEvolutions=0, newPokedexEntry=false, possibleEvoCountWithPreconditionsMet=0, possibleEvolutionCount=0, candyCount=0, sourceSpeciesTransferCount=0, evolutionLine={candyNeeded=25, precondition={buddyKm=0, preconditionType=NONE}, evolvedSpecies=375}, pokemonCount=0, sourceSpecies=374, evolvedSpeciesTransferCount=0} }

but they seem to never get through to the UI.

Here are the involved model classes, I'm using Lombok to generate getters, setters and the needed constructors (at least I hope I included everything needed). I already changed some fields from Enums to Strings, just in case this could be a problem... Caution: lots of code ahead...

CalculationInputEntry

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class CalculationInputEntry implements Comparable, Parcelable {

    //Pokédex number for less data redundancy when serializing
    private int sourceSpecies;
    private SpeciesEvolution evolutionLine;

    //input variables
    private int candyCount;
    private int pokemonCount;
    private boolean newPokedexEntry;
    private boolean preconditionsMet;

    //calculation and result variables
    private int possibleEvolutionCount; // 0 when preconditionsMet false
    private int sourceSpeciesTransferCount;
    private int evolvedSpeciesTransferCount;
    private int sourceSpeciesCountAfterEvolutions;
    private int possibleEvoCountWithPreconditionsMet;

    public CalculationInputEntry(int species, SpeciesEvolution evolution, int candyCount, int pokemonCount) {
        this.sourceSpecies = species;
        this.evolutionLine = evolution;
        this.candyCount = candyCount;
        this.pokemonCount = pokemonCount;
        this.preconditionsMet = false;
        this.newPokedexEntry = false;
    }

   //some other methods, including compareTo and the Parcelable stuff
}

SpeciesEvolution

@AllArgsConstructor
@NoArgsConstructor
@Getter
@Setter
public class SpeciesEvolution implements Parcelable {
    private int candyNeeded;
    private EvolutionPrecondition precondition;
    private int evolvedSpecies;

    //Parcelable stuff here
}

EvolutionPrecondition

@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
public class EvolutionPrecondition implements Parcelable {

    private String preconditionType;
    private int buddyKm;
    private String evoItem;

   //Parcelable stuff
}

Is there anything wrong with my models or am I just too blind to see the real problem? Any hint would be highly appreciated...

Answer 1

I solved it. Neither the start/stopListening is needed, nor are my getters/setters or the DatabaseReference wrong...

It's this line

mRecyclerView.setHasFixedSize(true);

after I had removed it, I could revert everything to the state shown in the question. I got the idea from this GitHub issue https://github.com/firebase/FirebaseUI-Android/issues/204 Thanks to Alex Mamo anyways :)