【Flutter/Dard】BMI計算アプリを作る

import 'package:flutter/material.dart';

void main() {
  runApp(BMICalculatorApp());
}

class BMICalculatorApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: BMICalculatorScreen(),
    );
  }
}

class BMICalculatorScreen extends StatefulWidget {
  @override
  _BMICalculatorScreenState createState() => _BMICalculatorScreenState();
}

class _BMICalculatorScreenState extends State<BMICalculatorScreen> {
  TextEditingController heightController = TextEditingController();
  TextEditingController weightController = TextEditingController();
  String bmiResult = "";
  String bmiCategory = "";

  void calculateBMI() {
    double height = double.tryParse(heightController.text) ?? 0.0;
    double weight = double.tryParse(weightController.text) ?? 0.0;

    if (height > 0 && weight > 0) {
      double bmi = weight / ((height / 100) * (height / 100));
      setState(() {
        bmiResult = bmi.toStringAsFixed(2);
        bmiCategory = getBMICategory(bmi);
      });
    } else {
      setState(() {
        bmiResult = "";
        bmiCategory = "";
      });
    }
  }

  String getBMICategory(double bmi) {
    if (bmi < 18.5) {
      return "Underweight";
    } else if (bmi >= 18.5 && bmi < 24.9) {
      return "Normal";
    } else if (bmi >= 25 && bmi < 29.9) {
      return "Overweight";
    } else {
      return "Obese";
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('BMI Calculator'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            TextField(
              controller: heightController,
              keyboardType: TextInputType.number,
              decoration: InputDecoration(
                labelText: 'Height (cm)',
              ),
            ),
            SizedBox(height: 16.0),
            TextField(
              controller: weightController,
              keyboardType: TextInputType.number,
              decoration: InputDecoration(
                labelText: 'Weight (kg)',
              ),
            ),
            SizedBox(height: 16.0),
            ElevatedButton(
              onPressed: calculateBMI,
              child: Text('Calculate BMI'),
            ),
            SizedBox(height: 16.0),
            Text(
              'BMI: $bmiResult',
              style: TextStyle(fontSize: 24.0),
            ),
            Text(
              'Category: $bmiCategory',
              style: TextStyle(fontSize: 18.0),
            ),
          ],
        ),
      ),
    );
  }
}