How to update data in firebase

Question

I have made a query to retrieve specific data from my firebase. In this case its users score. How can I update the same value I have just retrieved?

Thanks for any help

//check the leaders and their scores, get the score of the current user
    DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders");
    Query query = leadersRef.orderByChild("uID").equalTo(mCurrentUser.getUid());
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {

            if(snapshot.exists()){
                    for (DataSnapshot child: snapshot.getChildren()) {
                        currentScore = child.child("Score").getValue(Integer.class);
                        Toast.makeText(RunningChallengeActivity.this,"Your current score: " + currentScore,Toast.LENGTH_LONG).show();
                    }
                }
                else {

                //if user has no points create new leader child and set score to 0
                final DatabaseReference newResult = leaderBoard.push();
                String username = mCurrentUser.getEmail();

                //trim email leaving just username
                int index = username.indexOf('@');
                username = username.substring(0,index);

                newResult.child("UserName").setValue(username);
                newResult.child("uID").setValue(mAuth.getCurrentUser().getUid());
                newResult.child("Score").setValue(0);

                }
            }

        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });

MariusBrave · Accepted Answer · 2017-04-08 14:40:11Z

//check the leaders and their scores, get the score of the current user
    final DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders");
    final Query query = leadersRef.orderByChild("uID").equalTo(mCurrentUser.getUid());
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {

            if(snapshot.exists()){
                for (DataSnapshot child: snapshot.getChildren()) {

                    //get the key of the child node that has to be updated
                    String postkey = child.getRef().getKey();

                    //update score
                    int new_score = currentScore + score;
                    leadersRef.child(postkey).child("Score").setValue(new_score);
                    Toast.makeText(RunningChallengeActivity.this,"Your current score: " + new_score +"",Toast.LENGTH_LONG).show();

                }
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });

Frank van Puffelen · Accepted Answer · 2017-04-08 14:03:34Z

1

Something like this:

DatabaseReference leadersRef = FirebaseDatabase.getInstance().getReference("Leaders");
Query query = leadersRef.orderByChild("uID").equalTo(mCurrentUser.getUid());
query.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot snapshot) {
        for (DataSnapshot child: snapshot.getChildren()) {
            currentScore = child.child("Score").getValue(Integer.class);
            child.getRef().child("Score").setValue(42);
        }
    }

If you want to set the new value of the score based on its current value, you'll want to use a database transaction instead.

answered Apr 8, 2017 at 14:03

Frank van Puffelen

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