code

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: BMICalculator(),
    );
  }
}

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

  @override
  State<BMICalculator> createState() => _BMICalculatorState();
}

class _BMICalculatorState extends State<BMICalculator> {
  TextEditingController heightController = TextEditingController();
  TextEditingController weightController = TextEditingController();

  double bmi = 0.0;

  bool showBmi = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('BMI Calculator'),
      ),
      body: Container(
        padding: EdgeInsets.all(20),
        child: Column(
          children: [
            TextField(
              decoration: const InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Enter Height in cm',
              ),
              controller: heightController,
            ),
            const SizedBox(
              height: 20,
            ),
            TextField(
              decoration: const InputDecoration(
                border: OutlineInputBorder(),
                labelText: 'Enter Weight in KG',
              ),
              controller: weightController,
            ),
            const SizedBox(
              height: 20,
            ),
            ElevatedButton(
              onPressed: () {
                setState(() {
                  double height = double.parse(heightController.text);
                  double weight = double.parse(weightController.text);
                  bmi = (weight / (height * height)) * 10000;
                  showBmi = true;
                });
              },
              child: Text(
                'Calculate',
                style: const TextStyle(
                  fontSize: 30,
                ),
              ),
            ),
            const SizedBox(
              height: 20,
            ),
            showBmi
                ? Text(
                    "bmi: " + bmi.toStringAsFixed(2),
                    style: TextStyle(
                      fontSize: 30,
                    ),
                  )
                : const SizedBox(),
          ],
        ),
      ),
    );
  }
}