CODEWITHSUNDEEP
androidfirebasefirebase-realtime-database
Ankush Kapoor
Ankush Kapoor

Reputation: 543

How to Add numbers directly on Firebase database in Android

On Firebase database I have a key - "Coins" and its value - "20". Now I want to add 5 to the value (ie coins) directly on the server.

So every time the user clicks the button the value of Coins should increment by 5 directly on the server. Is there any way to do so?

Upvotes: 0

Views: 1746

Answers (1)

Frank van Puffelen
Frank van Puffelen

Reputation: 599571

As Fattie commented, you'd use Firebase Database transactions for this. With a transaction, you get the client's best guess for the current value and return the new value based on that. So in your case:

coinsRef.runTransaction(new Transaction.Handler() {
    @Override
    public Transaction.Result doTransaction(MutableData mutableData) {
        long value = 0;
        if (mutableData.exists()) {
            value = mutableData.getValue(Long.class);
        }
        value = value + 5;
        mutableData.setValue(value);
        return Transaction.success(mutableData);
    }

    @Override
    public void onComplete(DatabaseError databaseError, boolean b,
                           DataSnapshot dataSnapshot) {
        Log.d(TAG, "runTransaction:onComplete:" + databaseError);
    }
});

Upvotes: 1

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