How to check when my widget screen comes to visibility in flutter like onResume in Android

All of the problems are solved.

Put an observer on the navigator from the root of the widget tree (materialappwidget).

If you need more explanation please follow this link:
https://api.flutter.dev/flutter/widgets/RouteObserver-class.html

I have implemented in my project and its working great @Sp4Rx

// Register the RouteObserver as a navigation observer.
final RouteObserver<PageRoute> routeObserver = RouteObserver<PageRoute>();

void main() {
  runApp(MaterialApp(
    home: Container(),
    navigatorObservers: [routeObserver],
  ));
}

class RouteAwareWidget extends StatefulWidget {
  State<RouteAwareWidget> createState() => RouteAwareWidgetState();
}

// Implement RouteAware in a widget's state and subscribe it to
// the
// RouteObserver.
class RouteAwareWidgetState extends State<RouteAwareWidget> with RouteAware {
  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    routeObserver.subscribe(this, ModalRoute.of(context));
  }

  @override
  void dispose() {
    routeObserver.unsubscribe(this);
    super.dispose();
  }

  @override
  void didPush() {
    // Route was pushed onto navigator and is now topmost route.
  }

  @override
  void didPopNext() {
    // Covering route was popped off the navigator.
  }

  @override
  Widget build(BuildContext context) => Container();
}