Auto-increment a value in Firebase

Question

How do I auto increment a value stored in Firebase from an Android client?

Currently: I declare int id = 1. When I increment, I see the values 2, 3 etc.

Answer 1

Here's an example method that increments a single counter. The key idea is that you are either creating the entry (setting it equal to 1) or mutating the existing entry. Using a transaction here ensures that if multiple clients attempt to increment the counter at the same time, all requests will eventually succeed. From the Firebase documentation (emphasis mine):

Use our transactions feature when working with complex data that could be corrupted by concurrent updates

public void incrementCounter() {
    firebase.runTransaction(new Transaction.Handler() {
        @Override
        public Transaction.Result doTransaction(final MutableData currentData) {
            if (currentData.getValue() == null) {
                currentData.setValue(1);
            } else {
                currentData.setValue((Long) currentData.getValue() + 1);
            }

            return Transaction.success(currentData);
        }

        @Override
        public void onComplete(FirebaseError firebaseError, boolean committed, DataSnapshot currentData) {
            if (firebaseError != null) {
                Log.d("Firebase counter increment failed.");
            } else {
                Log.d("Firebase counter increment succeeded.");
            }
        }
    });
}

Answer 2

A new feature is added to firestore to autoincrement values. As simple as

document("fitness_teams/Team_1").
  updateData(["step_counter" : FieldValue.increment(500)])

refer link: https://firebase.googleblog.com/2019/03/increment-server-side-cloud-firestore.html

Used below code in my project.

var firestore = Firestore.instance;
firestore.collection('student').document('attendance').updateData({'total_attendace': FieldValue.increment(1)});