1-) FLUTTER - genişlik olarak web sitesinde android gibi gözüksün

kaynak : https://docs.flutter.dev/get-started/codelab-web

açıklama : ortalar ve genişliğini küçültür.. kIsWeb demek web ise demek

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

child: Container(
  width: kIsWeb ? 600.0 : double.infinity,
  child: MaterialApp(
    theme: ThemeProvider.themeOf(themeContext).data,
      title: 'ROKET HİZMET',
      home: LoginPage(),
      debugShowCheckedModeBanner: false,
      onGenerateRoute: RouteGenerator.routeGenerator,
      builder: EasyLoading.init(),
  ),
),