Contador en Flutter con setState: ejercicio resuelto paso a paso

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import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(home: CounterPage());
  }
}

class CounterPage extends StatefulWidget {
  const CounterPage({super.key});

  @override
  State<CounterPage> createState() => _CounterPageState();
}

class _CounterPageState extends State<CounterPage> {
  int counter = 0;

  void increment() => setState(() => counter += 1);
  void decrement() => setState(() => counter -= 1);
  void reset() => setState(() => counter = 0);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Contador con setState')),
      body: Center(
        child: Text('$counter', style: const TextStyle(fontSize: 48)),
      ),
      floatingActionButton: Column(
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          FloatingActionButton(onPressed: increment, child: const Icon(Icons.add)),
          const SizedBox(height: 8),
          FloatingActionButton(onPressed: decrement, child: const Icon(Icons.remove)),
          const SizedBox(height: 8),
          FloatingActionButton(onPressed: reset, child: const Icon(Icons.refresh)),
        ],
      ),
    );
  }
}