Firestore Query not retrieving all items into firestore RecyclerView

Question

Currently i am only retrieving max size of items -1 from the Cloud Firestore meaning if there's 3 items it will only retrieve 2. May i know what i am doing wrong for retrieving the items from collection().document().collection()?

This is my Chapter Fragment which holds the RecyclerView in xml

public class ChapterFragment extends Fragment {
    FirebaseFirestore db;
    private RecyclerView recyclerView;
    private View view;
    private Query mQuery;
    private FirestoreRecyclerAdapter adapter;
    private String documentId;

    public ChapterFragment() {

    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        db = FirebaseFirestore.getInstance();
        view = inflater.inflate(R.layout.fragment_chapter, container, false);
        recyclerView = view.findViewById(R.id.chapter);
        //Query
            mQuery = db.collection("Book").document("1").collection("1").orderBy("Volume", Query.Direction.DESCENDING);
        //Options
            FirestoreRecyclerOptions<ChapterDetails> options = new FirestoreRecyclerOptions.Builder<ChapterDetails>()
                    .setQuery(mQuery,ChapterDetails.class)
                    .setLifecycleOwner(this)
                    .build();

        //ViewHolder
        adapter = new FirestoreRecyclerAdapter<ChapterDetails, ChapterDetailsViewHolder>(options) {
            @NonNull
            @Override
            public ChapterDetailsViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view2 = LayoutInflater.from(parent.getContext()).inflate(R.layout.chapter_list, parent , false);
                return new ChapterDetailsViewHolder(view2);
            }

            @Override
            protected void onBindViewHolder(@NonNull ChapterDetailsViewHolder holder, int position, @NonNull ChapterDetails model) {
                holder.volume.setText("volume " + model.getVolume());
                holder.PDF.setText(model.getPDF());
            }
        };

        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
        recyclerView.setAdapter(adapter);
        return view;
    }

    private class ChapterDetailsViewHolder extends RecyclerView.ViewHolder{

        private TextView volume;
        private TextView PDF;

        public ChapterDetailsViewHolder(@NonNull View itemView) {
            super(itemView);

            volume = itemView.findViewById(R.id.volume_number);
            PDF = itemView.findViewById(R.id.pdf_text);
        }
    }
}

This is the picture of my firestore:

This is my ChapterDetails

public class ChapterDetails {
    private String Volume,PDF;
    public ChapterDetails(){
        //empty
    }
    public ChapterDetails(String volume, String pdf) {
        Volume = volume;
        PDF = pdf;
    }

    public String getVolume() {
        return Volume;
    }

    public void setVolume(String volume) {
        Volume = volume;
    }

    public String getPDF() {
        return PDF;
    }

    public void setPDF(String PDF) {
        this.PDF = PDF;
    }


}

This is how it looks in the android emulator

EDIT 28/5/2020:

D/error: get failed with 
    com.google.firebase.firestore.FirebaseFirestoreException: Failed to get document from cache. (However, this document may exist on the server. Run again without setting source to CACHE to attempt to retrieve the document from the server.)
        at com.google.firebase.firestore.core.FirestoreClient.lambda$getDocumentFromLocalCache$9(com.google.firebase:firebase-firestore@@21.4.3:197)
        at com.google.firebase.firestore.core.FirestoreClient$$Lambda$9.then(Unknown Source:0)
        at com.google.android.gms.tasks.zzd.run(Unknown Source:5)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
I/TAG: Current value of i = 1
I/TAG: Current value of i = 2
I/TAG: Current value of i = 3
I/TAG: Current value of i = 4
I/TAG: Current value of i = 5
I/TAG: Current value of i = 6

apparently firestore is saying i created source CACHE? which i didn't

Answer 1

Firebase uses Java Bean style naming conventions when mapping the properties from your Java class to the fields in the Firestore database.

In this convention, your getVolume and setVolume methods map to a property/field called volume and getPDF and setPDF map to a property called pDF. You'll note that both names start with a lowercase letter, while in your document they start with an uppercase letter. And since those are different names, your class will never be able to read from this document.

You can control the mapping of properties to fields by using a `` annotation on the getters and setters. Something like this:

public class ChapterDetails {
    private String Volume,PDF;
    public ChapterDetails(){
        //empty
    }
    public ChapterDetails(String volume, String pdf) {
        Volume = volume;
        PDF = pdf;
    }

    @PropertyName("Volume")
    public String getVolume() {
        return Volume;
    }

    @PropertyName("Volume")
    public void setVolume(String volume) {
        Volume = volume;
    }

    @PropertyName("PDF")
    public String getPDF() {
        return PDF;
    }

    @PropertyName("PDF")
    public void setPDF(String PDF) {
        this.PDF = PDF;
    }
}

Also see:

• How to get User data Via User Model from firebase?
• The annotations in the Firestore documentation.
• A solution for the issue cased by naming the fields upper case in both database and model class.