Check if a key already exist in firebase

Question

I have some problems related to my database, and the docs seems a lot of confusing i can't figure out how to solve that, basicly i have my user data in the firebase, and i want to see if in my user with some id i already have the key username if yes i want to update with some data of my form, if no i want to add a value based on my form, but when i want to know how to check if the id already exist, i did this:

  auth = FirebaseAuth.getInstance();
        database = FirebaseDatabase.getInstance();
        myRef = database.getReference();
        userId = auth.getCurrentUser().getUid();
        user =  myRef.child("Users").child(userId);
        Log.d("test1",String.valueOf(user.child("age").getKey()));
        if(user.child("username").co){
            usernameTxt.setText(user.child("username").toString());
        }
        if(user.child("age") != -1){
            usernameTxt.setText(user.child("age").toString());
        }

http://stackoverflow.com/questions/38948905/how-can-i-check-if-a-value-exists-already-in-a-firebase-data-class-anroid http://stackoverflow.com/questions/24824732/test-if-a-data-exist-in-firebase Check these — Mukeshkumar S, Apr 12 '17 at 13:56
what is that datasnapshot, i don't understand very well the docs — , Apr 12 '17 at 13:58
i don't understand very well what i need to do basicly i want to insert the username if it not exist and update if it exist — , Apr 12 '17 at 14:09
no atm im simple using normal login and created a new child where i register a user — , Apr 12 '17 at 14:32

score 2 · Accepted Answer · answered Apr 12 '17 at 14:33

2

Try this

final FirebaseAuth auth = FirebaseAuth.getInstance();
    DatabaseReference mDatabase=FirebaseDatabase.getInstance().getReference().child("Users").child(auth.getCurrentUser().getUid());
    mdatabase.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            if(dataSnapshot.hasChild("username")){
                //IT EXISTS
            }
            else{
                //IT DOESNT EXISTS
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

answered Apr 12 '17 at 14:33

Martin De Simone

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i feel i almost did it, but how can i retrive a single value of snapshot? i did this: dataSnapshot.child("username").getValue(), inspected that with logcat and it gives me this: https://friendlymanager-3b7a2.firebaseio.com/Users/g7LWSXBP2WYwBbDqPS82oEpILA22/username :S – Apr 12 '17 at 15:08
You have to cast it use getValue(String.class); – Martin De Simone Apr 12 '17 at 16:01
Have you tested my answer? – Martin De Simone Apr 12 '17 at 16:03
yeah i did it, i will accept the answer, a last question, i have a User model in a separate file and i save the data using it, i saw some examples where they use the dataSnapshot with the model, in this case can i do it to do a better approach?´ – Apr 12 '17 at 16:15
Do you want to get the data or write it? – Martin De Simone Apr 12 '17 at 17:19
i want to get it to display on my activity, and then when i press update data, add or update the data on firebase, but in this example i just want to get – Apr 12 '17 at 17:24
Use getValue (Yourmodel.class) in the dataSnaphot – Martin De Simone Apr 12 '17 at 17:39
can i add you to chat ? – Apr 12 '17 at 17:45
Yes, i dont have any problem – Martin De Simone Apr 12 '17 at 18:49
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/141583/discussion-between-filipe-costa-and-martin-de-simone). – Apr 12 '17 at 19:20

Check if a key already exist in firebase

1 Answers1