Spacer as Named Constant

main.dart

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

// Declares the SizedBox as a named constant
const SizedBox mySpacer = SizedBox(height: 20);

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) => const MaterialApp(
        debugShowCheckedModeBanner: false,
        home: Scaffold(
          body: Center(
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text('Item 1'),
                mySpacer, // Using the spacer
                Text('Item 2'),
                mySpacer, // Using the spacer again
                Text('Item 3'),
              ],
            ),
          ),
        ),
      );
}