Passed SessionConfig as Dependency Injection and added timer for app losing focus

session_timeout_manager.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'session_config.dart';

class SessionTimeoutManager extends StatefulWidget {
  final SessionConfig _sessionConfig;
  final Widget child;


  const SessionTimeoutManager(
      {Key? key,
      required sessionConfig,
      required this.child,
      })
      : _sessionConfig = sessionConfig,
        super(key: key);

  @override
  _SessionTimeoutManagerState createState() => _SessionTimeoutManagerState();
}

class _SessionTimeoutManagerState extends State<SessionTimeoutManager>
    with WidgetsBindingObserver {
  Timer? _appLostFocusTimer;
  Timer? _userInactivityTimer;

  bool _userTapActivityRecordEnabled = true;

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

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    super.didChangeAppLifecycleState(state);

    if (state == AppLifecycleState.inactive ||
        state == AppLifecycleState.paused) {
      if (widget._sessionConfig.invalidateSessionForAppLostFocus != null) {
        _appLostFocusTimer ??= _setTimeout(
          () => widget._sessionConfig.pushAppFocusTimeout(),
          duration: widget._sessionConfig.invalidateSessionForAppLostFocus!,
        );
      }
    } else if (state == AppLifecycleState.resumed) {
      if (_appLostFocusTimer != null) {
        _clearTimeout(_appLostFocusTimer!);
        _appLostFocusTimer = null;
      }
    }
  }

  @override
  Widget build(BuildContext context) {

    return widget.child;
  }

  Timer _setTimeout(callback, {required Duration duration}) {
    return Timer(duration, callback);
  }

  void _clearTimeout(Timer t) {
    t.cancel();
  }
}