dynamic_link_3.dart

class _MyHomeWidgetState extends State<_MyHomeWidget> with WidgetsBindingObserver{
  .
  Timer _timerLink;
  .
  .
  @override
  void initState() {
    super.initState();
     WidgetsBinding.instance.addObserver(this);
  }

    @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
        _timerLink = new Timer(const Duration(milliseconds: 850), () {
        _retrieveDynamicLink();
      });
    }
  }

  Future<void> _retrieveDynamicLink() async {
    final PendingDynamicLinkData data = await FirebaseDynamicLinks.instance.retrieveDynamicLink();
    final Uri deepLink = data?.link;

    if (deepLink != null) {
      Navigator.pushNamed(context, deepLink.path); // '/helloworld'
    }
  }
  .
  .
  .
  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    if (_timerLink != null) {
      _timerLink.cancel();
    }
    super.dispose();
  }
}