Trigger an action by observing user interaction, in our case we want to auto log a user out if he stops interacting with the app within a duration using listener.

time_based_logout.dart

/// Define top level functions at any suitable location "I did in a separate dart file"

Timer sessionTimer;

/// intialize a timer to trigger a function after a period of inactiveness
void initializeTimer() {
  sessionTimer =
      Timer.periodic(const Duration(minutes: 5), (_) => UserUtil.logOut());
}

/// Will be called to reset the timer when some pointer events are emitted.
void handleUserInteraction([_]) {
  // Check if the user is logged in and session timer is not null
  if (CustomerState.sessionDetails.isLoggedIn && sessionTimer != null) {
    if (!sessionTimer.isActive) {
      return;
    }

    /// if timer is active cancel the previous timer
    /// then initiale a new one
    sessionTimer.cancel();
    initializeTimer();
  }
}

/*
* --- NOTE ---
* The session timer needs to be activated
* For my use case i activated it by invoking "initializeTimer()"
* When a user login in successfully.
*/

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
  /// Wrap the material app with a listener and trigger function(s) on listener's pointer events
    return Listener(
        /// Check the properties on the listner official documentation
        /// to understands the pointers handled
        /// the most imporant to me are Down & Move
        onPointerDown: handleUserInteraction,
        onPointerUp: handleUserInteraction,
        onPointerMove: handleUserInteraction,
      child: MaterialApp(...),
    );
  }
}
/*
*--- Resources ---
* https://flutter.dev/docs/development/ui/advanced/gestures#adding-gesture-detection-to-widgets
* https://api.flutter.dev/flutter/widgets/Listener-class.html
*/

Oh.
I initialize the sessionTime out when a user logs in successfully.

I will add a comment.