1-) FLUTTER - platform web ise veya mobil ise How can I detect if my Flutter app is running in the web

import 'package:flutter/foundation.dart' show kIsWeb;

if (kIsWeb) {
// running on the web!
} else {
// NOT running on the web! You can check for additional platforms here.
}

kaynak : https://stackoverflow.com/questions/57937280/how-can-i-detect-if-my-flutter-app-is-running-in-the-web

AYRICA WEBDE ÇİRKİN DURMAMASI İÇİN KAYNAK :

https://www.kindacode.com/article/using-navigationrail-and-bottomnavigationbar-in-flutter/

diğer kaynak :

 https://stackoverflow.com/questions/67564434/flutter-web-create-ui-with-mobile-app-size

Center(

  child: Container(

    width: kIsWeb ? 400.0 : double.infinity,

    child: ListView.builder(...)

  ),

);