How to save users score in firebase and retrieve it in real-time in Android studio

Question

I am creating an app in which points increases on button click and those points should be saved to firebase. I managed to save those data to firebase. But when I destroy my

Answer 1

Edit: 29th, June 2020

Now it's also possible to solve this problem without the use of a transaction. We can simply increment a value using:

rootRef.child("score").setValue(ServerValue.increment(1));

And for decremenet, the following line of code is required:

rootRef.child("score").setValue(ServerValue.increment(-1));

---

This is how you set a value in your Firebase database:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
rootRef.child("score").setValue(1);

Assuming that the your score field is of type Integer, to solve this, please use the following method:

public static void setScore(String operation) {
    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    DatabaseReference scoreRef = rootRef.child("score");
    scoreRef.runTransaction(new Transaction.Handler() {
        @Override
        public Transaction.Result doTransaction(MutableData mutableData) {
            Integer score = mutableData.getValue(Integer.class);
            if (score == null) {
                return Transaction.success(mutableData);
            }

            if (operation.equals("increaseScore")) {
                mutableData.setValue(score + 1);
            } else if (operation.equals("decreaseScore")){
                mutableData.setValue(score - 1);
            }

            return Transaction.success(mutableData);
        }

        @Override
        public void onComplete(DatabaseError databaseError, boolean b, DataSnapshot dataSnapshot) {}
    });
}

For this, I recommend you definitely use transactions. You will avoid wrong results if users are trying to increase/decrease the score in the same time. So as a conclusion, call this method accordingly to your increase/decrease operation.

This is how you can read it:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference scoreRef = rootRef.child("score");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Integer score = ds.getValue(Integer.class);
        Log.d("TAG", score + "");
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
scoreRef.addListenerForSingleValueEvent(eventListener);

Answer 2

You need to first get the value of previous score and then add it with the current score and then update the final value in the firebase database.

question_score.child("score").addValueEventListener(new ValueEventListener() {
                        @Override
                        public void onDataChange(DataSnapshot dataSnapshot) {
                            String previousScore = dataSnapshot.getValue(String.class);
                            if (previousScore!=null){
                                int finalScore = Integer.parseInt(previousScore) + current_score;
                                question_score.child("score").setValue(String.valueOf(finalScore));
                            }
                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError) {

                        }
                    });

Answer 3

I think that previous score is a string in you code @DHANANJAY KUMAR and Strings cannot be added and also what is the meaning of String.class. I think It can be made

int previousScore = dataSnapshot.getValue(Integer.class);

if we can edit

String.class

to

Integer.class

or

int.class

Please Clarify