main.dart

import 'package:flutter/material.dart';

final 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),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: Builder(
            builder: (context) {
              return GestureDetector(
                onLongPress: () {
                  Scaffold.of(context).showSnackBar(SnackBar(content: Text('primary')));
                },
                onSecondaryLongPress: () {
                  Scaffold.of(context).showSnackBar(SnackBar(content: Text('secondary')));
                },
                child: MyWidget(),
              );
            },
          ),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('Hello, World!', style: Theme.of(context).textTheme.headline4);
  }
}