集合引用无效。 集合引用必须有奇数个段

Question

I want to get all documents from a sub-collection.

Here's the path:

Collection(Shops)-Doc(shop)-Collection(year)-Doc(month)-Col(day)-Doc(Current)-Col(initial stocks).

This is how it looks like in firestore:

Numbers - Dhool - 2021 - 10(month) - 06(day) - Begining - initial stock

But I'm getting the following error:

I know there are other questions like that but they are not solving my problems.

Here is the code of the fragment where the query is:

public class DebutFragment extends Fragment {

Calendar calendar;
DatePickerDialog.OnDateSetListener date;
TextView dateView;

String day="", month="", year="";

public DebutFragment() {}

public static DebutFragment newInstance() {
    return new DebutFragment();
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_actuel, container, false);
    dateView = view.findViewById(R.id.date);

    this.configureDate();
    day = getDay(choosenDate);
    month = getMonth(choosenDate);
    year = getYear(choosenDate);

    this.configureRecyclerView(view);

    return view;
}

/////////////
//////////
private void configureDate() {
    calendar = Calendar.getInstance();
    date = (view, year, month, dayOfMonth) -> {
        calendar.set(Calendar.YEAR, year);
        calendar.set(Calendar.MONTH, month);
        calendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);

        updateLabel();
    };

    updateLabel();

    dateView.setOnClickListener(v -> new DatePickerDialog(getContext(), date,
            calendar.get(Calendar.YEAR), calendar.get(Calendar.MONTH), calendar.get(Calendar.DAY_OF_MONTH)).show());
}

private void updateLabel() {
    SimpleDateFormat dateFormatAbreger = new SimpleDateFormat("E dd MMM yy", Locale.FRANCE);
    SimpleDateFormat simpleDateFormat = new SimpleDateFormat(BIRTHDAY_FORMAT, Locale.FRANCE);
    dateView.setText(dateFormatAbreger.format(calendar.getTime()));
    choosenDate = simpleDateFormat.format(calendar.getTime());
}

//////////////////
private void configureRecyclerView(View view) {
    RecyclerView recyclerView = view.findViewById(R.id.khat_debut_recyclerview);
    KhatDebutAdapter adapter = new KhatDebutAdapter(options);
    recyclerView.setAdapter(adapter);
    recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

    adapter.notifyDataSetChanged();
}

Query query = getKhatInitialeCollectionReference(day, month, year).orderBy("typ", Query.Direction.ASCENDING);
FirestoreRecyclerOptions<Khat> options = new FirestoreRecyclerOptions.Builder<Khat>()
        .setQuery(query, Khat.class).setLifecycleOwner(this).build();
  }

Here is the code of all my Firebase methods:

public class FirebaseCalls {

//BOSSES
public static CollectionReference getBossesCollectionReference() {
    return FirebaseFirestore.getInstance().collection(PATRONS);
}

public static DocumentReference getBossDocumentReference(String emailBoss) {
    return getBossesCollectionReference().document(emailBoss);
}

//NUMBERS
public static CollectionReference getNumbersBigCollectionReference() {
    return FirebaseFirestore.getInstance().collection(NUMBERS);
}

public static CollectionReference getNumbersCollectionReference() {
    return getBossDocumentReference(currentBoss.getEmail()).collection(NUMBERS);
}

public static DocumentReference getNumberDocumentReference(String name) {
    return getNumbersCollectionReference().document(name);
}

public static DocumentReference getNumberBigDocumentReference() {
    return getNumbersBigCollectionReference().document(currentNumber.getName());
}

///YEAR
public static CollectionReference getYearCollectionReference(String year) {
    return getNumberBigDocumentReference().collection(year);
}

///MONTH
public static DocumentReference getMonthDocumentReference(String month, String year) {
    return getYearCollectionReference(year).document(month);
}

public static CollectionReference getDayCollectionReference(String day, String month, String year) {
    return getMonthDocumentReference(month, year).collection(day);
}

///COMMENCEMENT
public static DocumentReference getCommencementDocumentReference(String day, String month, String year) {
    return getDayCollectionReference(day, month, year).document(COMMENCEMENT);
}

///RESTANT
public static DocumentReference getRestantDocumentReference(String day, String month, String year) {
    return getDayCollectionReference(day, month, year).document(RESTANT);
}

Can somebody help me, please?

Answer 1

This issue, as you mentioned, is already pointed out in different questions, and it's related to the Firestore data model. Here you can find detailed information about how this data model is structured. Basically, the error says you can't have an odd number of segments to refer to a collection; this is because collections are always going to be in an odd position due to how hierarchy structures are designed. The documentation says:

Notice the alternating pattern of collections and documents. Your collections and documents must always follow this pattern. You cannot reference a collection in a collection or a document in a document.

You can see the pattern here:

And here is an example used in the documentation implemented in a Chat Application to explain Hierarchy structure:

To understand how hierarchical data structures work in Cloud Firestore, consider an example chat app with messages and chat rooms. You can create a collection called “rooms” to store different chat rooms:

And this is how it's referenced:

 DocumentReference messageRef = db.collection("rooms").document("roomA").collection("messages").document("message1");

This, compared to your application, will be:

Numbers - Dhool - 2021(year) - 10(month) - 06(day) - Beginning - initial stock

• Collection: Numbers
• Document: Dhool
• Subcollection: 2021(year)
• Document: 10(month)
• Subcollection: 06(day)
• Document: Beginning
• Subcollection: Initial Stock

And should be referenced in this way:

CollectionReference NumbersColRef = db.Collection(“Numbers”);
DocumentReference DhoolDocRef = NumbersColRef().Document(“Dhool”);
CollectionReference YearColRef = DhoolDocRef().Collection(“Year”);
DocumentReference MonthDocRef = YearColRef().Document(“Month”);
CollectionReference DayColRef = MonthDocRef().Collection(“Day”);
DocumentReference BeginningDocRef = DayColRef().Document(“Beginning”);
CollectionReference IStockColRef = BeginningDocRef().Collection(“IStock”);

If your structure is already like this, which I can see it is, the error may also occur when the references are not properly called or if one of them is empty or returning an empty or incorrect format value, which might be the case. You can troubleshoot your parameters and see if they are correctly called and also check the entity IDs if they return a type of value format that might cause a problem. The dates may contain a “/” or another symbol that could cause the program to crash, so be sure to parse it to Strings or Integers, or that the values are not being received in a format that could cause this issue. This was found in another forum with the same error, but the cause was a little different from what the error says. Please take in consideration this is not from the official documentation.