Implement realtime online/offline status with flutter and firebase

Question

Hy, what is the best way to show in an app if the user is online or offline?

Frontend -> Flutter

Backend -> Firestore Cloud and Firebase Auth.

I have a collection of users in firestore that contains documents. Each document is a user and contain "status" field. In flutter i can update this field every time that user sign in or log out but if you close the app it is not updated.

Answer 1

You can extend your statefulWidget State class with WidgetsBindingObserver like

class _HomePageState extends State<HomePage>
    with WidgetsBindingObserver

and initState method add WidgetsBinding.instance.addObserver(this);.

@override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

Later overide didChangeAppLifecycleState method

@override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed)
      //TODO: set status to online here in firestore
    else
      //TODO: set status to offline here in firestore
  }