Counter

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,
      ),
      debugShowCheckedModeBanner: false,
      home: const Scaffold(
        body: Center(
          child: Counter(),
        ),
      ),
    );
  }
}

class Counter extends StatefulWidget {
  const Counter({Key? key}) : super(key: key);

  @override
  ConuterState createState() => ConuterState();
}

class ConuterState extends State<Counter> {
  int count = 0;

  @override
  Widget build(BuildContext context) {
    return Column(mainAxisSize: MainAxisSize.min, children: [
      Text("$count", style: const TextStyle(fontSize: 30)),
      const SizedBox(height: 40),
      Row(mainAxisAlignment: MainAxisAlignment.center, children: [
        TextButton(child: const Text("increase"), onPressed: increase),
        const SizedBox(width: 40),
        TextButton(child: const Text("decrease"), onPressed: decrease)
      ])
    ]);
  }

  void increase() {
    setState(() {
      count += 1;
    });
  }

  void decrease() {
    setState(() {
      count -= 1;
    });
  }
}