Counter example

readme.md

Counter example

Created with <3 with dartpad.dev.

main.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({
    Key? key,
    required this.title,
  }) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  // Using 'int' to represent whole numbers (e.g., count of items)
  int itemCount = 0;

  // Using 'double' for precise calculations (e.g., item price)
  double itemPrice = 5.99;

  // Using 'num' for flexibility (e.g., total cost may include whole and fractional parts)
  num totalCost = 0;

  void _incrementCounter() {
    // Increment the item count when the button is pressed
    setState(() {
      itemCount++;
      // Calculate the total cost using 'num'
      totalCost = itemCount * itemPrice;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Counter App'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              'Item Count: $itemCount',
              style: TextStyle(fontSize: 20),
            ),
            SizedBox(height: 20),
            Text(
              'Total Cost: \$${totalCost.toStringAsFixed(2)}',
              style: TextStyle(fontSize: 20),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: () {
                _incrementCounter();
              },
              child: Text('Add Item'),
            ),
          ],
        ),
      ),
    );
  }
}