Firebase - Count online users

Question

I tried playing about with presence to make it display the total connected users in an element. I couldn't really figure out where to look. I did something similar to this:

var dataUlist = new Firebase('https://<url>.firebaseio.com/.info/connected');
dataUlist.on('value', function(snap) {
    console.log(snap);
});

To try and see if I could find anything useful in there, but (I kinda expected it) I couldn't make any sense of the data.

Is there any way to accomplice what I am after? Fetch the total number of connected users and eg. echo it out in the console or to an element? Or maybe how to fetch a list of authorised users and non-authorised?

EDIT: I would like to keep my spelling in English, I am not American. Thank you.

Answer 1

.info/connected will only return information about whether the current client is connected or not. In order to maintain a presence count, you'll need to create a counter by storing presence information for each user and utilizing setOnDisconnect(). For example:

var listRef = new Firebase("https://<url>.firebaseio.com/presence/");
var userRef = listRef.push();

// Add ourselves to presence list when online.
var presenceRef = new Firebase("https://<url>.firebaseio.com/.info/connected");
presenceRef.on("value", function(snap) {
  if (snap.val()) {
    // Remove ourselves when we disconnect.
    userRef.onDisconnect().remove();

    userRef.set(true);
  }
});

// Number of online users is the number of objects in the presence list.
listRef.on("value", function(snap) {
  console.log("# of online users = " + snap.numChildren());
});    

Answer 2

Here is the the code from Anant formatted for Android

public void getDbCount() {

    Firebase listRef = new Firebase("https://<your-firebase-database>.firebaseio.com/presence/");
    final Firebase userRef = listRef.push();

    // Add ourselves to presence list when online.
    Firebase presenceRef = new Firebase("https://<your-firebase-database>.firebaseio.com/.info/connected");

    ValueEventListener myPresence = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            // Remove ourselves when we disconnect.
            userRef.onDisconnect().removeValue();
            userRef.setValue(true);
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {
            Log.e("DBCount", "The read failed: " + firebaseError.getMessage());
        }
    };

    presenceRef.addValueEventListener(myPresence);

    // Number of online users is the number of objects in the presence list.
    ValueEventListener myList = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            // Remove ourselves when we disconnect.
            Log.i("DBCount", "# of online users = " + String.valueOf(snapshot.getChildrenCount()));
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {
            Log.e("DBCount", "The read failed: " + firebaseError.getMessage());
        }
    };

    listRef.addValueEventListener(myList);
}