android firebase query sub-object across multiple objects

Question

I am trying to find a session with a specific id (not key) without knowing the user id.

Database Structure

I had an initial attempt by looping through all the children of users and creating a new reference every time but it is not working and I can't figure out why nor I know if it should work in the first place.

 database.child("users").addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for(DataSnapshot snap : dataSnapshot.getChildren()){
                        database.child("users").child(snap.getKey()).child("sessions")
                                .orderByChild("id").equalTo(id)
                                .limitToFirst(1)
                                .addListenerForSingleValueEvent(new ValueEventListener() {
                                    @Override
                                    public void onDataChange(DataSnapshot data) {
                                        if (data.exists()) {
                                            Session session = data.getValue(Session.class);
                                        }
                                    }

                                    @Override
                                    public void onCancelled(DatabaseError databaseError) {

                                    }
                        });
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

You may use log to be more specific where your issue is

user6490462
– user6490462

2017-05-10 22:36:32 +00:00
Commented May 10, 2017 at 22:36 — user6490462
– user6490462, Commented May 10, 2017 at 22:36

Alex Mamo · Accepted Answer · 2017-05-11 10:55:05Z

1

The whole idea of what you are trying to do is correct but you have a single mistake. Your last reference is wrong. When you are trying to iterate the second time you are missing a child. You need to add .child(sessionId). To solve this, please use this code:

database.child("users").child(snap.getKey()).child("sessions").child(sessionId)
                            .orderByChild("id").equalTo(id)
                            .limitToFirst(1)

In which sessionId is the second unique id generated by the push() method.

Hope it helps.

answered May 11, 2017 at 10:55

Alex Mamo

139k18 gold badges171 silver badges202 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Cosmin Argatu Over a year ago

Thanks for the help. The whole point of what I was trying to do is that I don't have the sessionId. I only have the more user friendly id, which is not the same thing, and I'm trying to find sessionId (well actually get the whole session).

Alex Mamo Over a year ago

You have the sessionId, as i see it in your database. Is the unique key under the sessions node. To get it, use the getKey() on your reference in the exact moment when you are using the second push() method. Having that sessionId, you'll be able to use it in your DatabaseReference.

Cosmin Argatu · Accepted Answer · 2017-05-11 08:25:19Z

0

Issue caused by permission denied from Firebase.

answered May 11, 2017 at 8:25

Cosmin Argatu

282 bronze badges

Collectives™ on Stack Overflow

android firebase query sub-object across multiple objects

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related