Firebase getting value returns NULL value

Question

So I have a database in this format:

I need to be able to get the name, price and quantity after I search the database for the barcode.

I tried something like this:

    mFirebaseInstance = FirebaseDatabase.getInstance();
    mFirebaseDatabase = mFirebaseInstance.getReference("ProductData");
    UserId = mFirebaseDatabase.push().getKey();

public void searchProduct(String barcode){
    mFirebaseDatabase.child("Products").child("barcode").equalTo(barcode).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            Log.d("DBVAL", String.valueOf(dataSnapshot.getValue()));
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    });

Here is the output:

D/DBVAL: null

user_5246885 · Answer

You are getting that result because you aren't using the correct query. Besides that, there is no node in your database named DataUsers. To get all children that contains a particular barcode, please use the following query:

Query barcodeQuery = mFirebaseDatabase.child("ProductData").child("Products")
        .orderByChild("barcode").equalTo(barcode);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String name = ds.child("name").getValue(String.class);
            int price = ds.child("price").getValue(Integer.class);
            int quantity = ds.child("quantity").getValue(Integer.class);
            Log.d("TAG", name + "/" + price + "/" + quantity);
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d("TAG", databaseError.getMessage()); //Don't ignore errors!
    }
};
barcodeQuery.addValueEventListener(valueEventListener);

See, I have added in this query both nodes ProductData and Products, and then I order all children by barcode property and used .equalTo(barcode).

Firebase getting value returns NULL value

1 Answers