Notes

import 'package:flutter/material.dart';

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

class BmiCalculator extends StatefulWidget {
@override
_BmiCalculatorState createState() => _BmiCalculatorState();
}

class _BmiCalculatorState extends State<BmiCalculator> {
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text('Beautiful Places!'),
),
body: Column(
children: <Widget>[
Expanded( //this is the first two row column
child: Row(
children: <Widget>[

Expanded(
child: Container(
margin: EdgeInsets.all(15.0),
decoration: BoxDecoration(
color: Colors.black45,
borderRadius: BorderRadius.circular(10.0),
),
),
),
],
),
),
// now this is next row down to 2 coloumns
Expanded(
child: Row(
children: <Widget>[
Expanded(
child: Container(
margin: EdgeInsets.all(15.0),
decoration: BoxDecoration(
color: Colors.black45,
borderRadius: BorderRadius.circular(10.0),
),
),
),
],
),
),

Expanded( // now these two columns are bottom of the screen
child: Row(
children: <Widget>[
Expanded(
child: Container(
margin: EdgeInsets.all(15.0),
decoration: BoxDecoration(
color: Colors.black45,
borderRadius: BorderRadius.circular(10.0),
),
),
),
Expanded(
child: Container(
margin: EdgeInsets.all(15.0),
decoration: BoxDecoration(
color: Colors.black45,
borderRadius: BorderRadius.circular(10.0),
),
),
),
],
),
),
],
),
),
);
}
}

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

// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.

// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".

final String title;

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

class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;

void _incrementCounter() {
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}

@override
Widget build(BuildContext context) {
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}