Flutter Material 3 full screen dialog

main.dart

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark()
          .copyWith(scaffoldBackgroundColor: darkBlue, useMaterial3: true),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(
        child: OutlinedButton(
            onPressed: () {
              showDialog(
                  context: context,
                  builder: (context) {
                    return Dialog.fullscreen(
                      backgroundColor: Colors.white,
                      child: Center(
                        child: TextButton(
                            onPressed: () {
                              Navigator.of(context).pop();
                            },
                            child: const Text("Close")),
                      ),
                    );
                  });
            },
            child: const Text("Open fullscreen dialog")));
  }
}