Responsive Widgets Prefix allows you to add the Responsive prefix to any widget that needs scaling or font size increases

          ...
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],

          ...
          children: <Widget>[
            ResponsiveText(
              'You have pushed the button this many times:',
            ),
            ResponsiveText(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],

          ...
          children: <Widget>[
            ResponsiveText(
              'You have pushed the button this many times:',
            ),
            ResponsiveText(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
              scaleMediumTablet: 4,
            ),
          ],

  flutter pub get responsive_widgets_prefix

    ...
    
dependencies:
  flutter:
    sdk: flutter

    ...

  responsive_widgets_prefix: <latest_version>

import 'package:responsive_widgets_prefix/responsive_widgets_prefix.dart';

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return ResponsiveMaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return ResponsiveCupertinoApp(
      title: 'Flutter Demo',
      theme: CupertinoThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primaryColor below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primaryColor: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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

class PlatformApp extends PlatformWidget {

  PlatformApp({
    Key? key,
    required MaterialApp androidApp,
    required CupertinoApp iosApp,
    required TargetPlatform defaultPlatform,
  }) : super(key: key,
      androidBuilder: (BuildContext context) => androidApp,
      iosBuilder:  (BuildContext context) => iosApp
    ) {
      PlatformWidget.setPlatform(defaultPlatform);
  }

}

class PlatformWidget extends StatefulWidget {
  
  static TargetPlatform? _defaultPlatform;

  static get platform {
      if(_defaultPlatform == null) {
        return TargetPlatform.android;
      }
      return _defaultPlatform;
  }

  static get isAndroid {
      return _defaultPlatform == TargetPlatform.android;
  }

  static get isIOS {
      return _defaultPlatform == TargetPlatform.iOS;
  }

  static void setPlatform(TargetPlatform platform) {
      _defaultPlatform = platform;
  }

  static void reassembleApplication() {
      WidgetsBinding.instance!.reassembleApplication();
  }

  const PlatformWidget({
    Key? key,
    required this.androidBuilder,
    required this.iosBuilder,
  }) : super(key: key);

  final WidgetBuilder androidBuilder;
  final WidgetBuilder iosBuilder;

  @override
  State<PlatformWidget> createState() => _PlatformWidgetState();
}

class _PlatformWidgetState extends State<PlatformWidget> {
  @override
  Widget build(context) {
    switch (PlatformWidget._defaultPlatform) {
      case TargetPlatform.android:
        return widget.androidBuilder(context);
      case TargetPlatform.iOS:      
        return widget.iosBuilder(context);        
      default:
        assert(false, 'Unexpected platform ${PlatformWidget._defaultPlatform}');
        return Container();
    }
  }
}

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:responsive_widgets_prefix/responsive_widgets_prefix.dart';

import 'platforms.dart';

void main() => runApp(setupMainWidget());

Widget setupMainWidget() {
  WidgetsFlutterBinding.ensureInitialized();
  return const MyApp();
}
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override Widget build(BuildContext context) {
    return PlatformApp(
        defaultPlatform: PlatformWidget.platform,
        androidApp: ResponsiveMaterialApp(
          theme: ThemeData(primarySwatch: Colors.blue),
          home: const MyHomePage(title: 'Counter Sample')
        ),
        iosApp: ResponsiveCupertinoApp(
            theme: const CupertinoThemeData(primaryColor: Colors.blue),
            home: const MyHomePage(title: 'Counter Sample'),
        )
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;
  const MyHomePage({Key? key, required this.title}) : super(key: key);
  @override State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }
  @override Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.title)),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            ResponsiveText('You have pushed the button this many times:'),
            ResponsiveText('$_counter', style: Theme.of(context).textTheme.headline4, scaleMediumTablet: 4),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter, tooltip: 'Increment', child: const Icon(Icons.add),
      ),
    );
  }
}