react native with firestore get count online users - firebase

Question

I build app in react native with firebase/firestore.
I'm looking a way to check the count of users online in app, so I found a way to do with this tutorial
var userRef = new Firebase('https://<demo>.firebaseio.com/presence/' + userid);
userRef.on('value', function(snapshot) {
if (snapshot.val() === true) {
// User is online, update UI.
} else {
// User logged off at snapshot.val() - seconds since epoch.
}
});
I'm looking a way to do with firestore and react native. is there any implementation i can see how do that?
I found this way to do with firestore
import { Platform } from 'react-native';
import firebase from 'react-native-firebase';
function rtdb_and_local_fs_presence() {
// [START rtdb_and_local_fs_presence]
// [START_EXCLUDE]
var uid = firebase.auth().currentUser.uid;
console.log('uid',uid)
var userStatusDatabaseRef = firebase.database().ref('status/' + uid);
var isOfflineForDatabase = {
state: 'offline',
last_changed: firebase.database.ServerValue.TIMESTAMP,
};
var isOnlineForDatabase = {
state: 'online',
last_changed: firebase.database.ServerValue.TIMESTAMP,
};
// [END_EXCLUDE]
var userStatusFirestoreRef = firebase.firestore().doc('status/' + uid);
// Firestore uses a different server timestamp value, so we'll
// create two more constants for Firestore state.
var isOfflineForFirestore = {
state: 'offline',
last_changed: firebase.firestore.FieldValue.serverTimestamp(),
};
var isOnlineForFirestore = {
state: 'online',
last_changed: firebase.firestore.FieldValue.serverTimestamp(),
};
firebase.database().ref('.info/connected').on('value', function(snapshot) {
if (snapshot.val() == false) {
// Instead of simply returning, we'll also set Firestore's state
// to 'offline'. This ensures that our Firestore cache is aware
// of the switch to 'offline.'
userStatusFirestoreRef.set(isOfflineForFirestore);
return;
};
userStatusDatabaseRef.onDisconnect().set(isOfflineForDatabase).then(function() {
userStatusDatabaseRef.set(isOnlineForDatabase);
// We'll also add Firestore set here for when we come online.
userStatusFirestoreRef.set(isOnlineForFirestore);
});
});
// [END rtdb_and_local_fs_presence]
}
function fs_listen() {
var uid = firebase.auth().currentUser.uid;
var userStatusFirestoreRef = firebase.firestore().doc('status/' + uid);
// [START fs_onsnapshot]
userStatusFirestoreRef.onSnapshot(function(doc) {
var isOnline = doc.data().state == 'online';
// ... use isOnline
});
}
firebase.auth().signInAnonymouslyAndRetrieveData().then((user) => {
rtdb_and_local_fs_presence();
fs_listen();
});
it really update the status collection with the right uid when I'm online, but when I disconnect from app, it not update to offline. how can I do that?

Answer 1

It will be working when user closes the app completly.
onStatusOffline(user){
firebase.database().ref(`users/${user.uid}`)
.onDisconnect()
.update({
online: false,
});
}