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| import 'package:flutter/material.dart';
import 'package:math_expressions/math_expressions.dart';
void main() {
runApp(const MainApp());
}
class MainApp extends StatelessWidget {
const MainApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(
colorSchemeSeed: Color(0xffaaaa22),
useMaterial3: true,
),
home: Scaffold(
body: Homepage(),
),);}
}
class Homepage extends StatefulWidget {
const Homepage({super.key});
@override
State<Homepage> createState() => _HomepageState();
}
class _HomepageState extends State<Homepage> {
String _userInput = "";
String _answer = "";
final List<String> buttons = [
'C', '±', '%', 'DEL',
'7', '8', '9', '/',
'4', '5', '6', '*',
'1', '2', '3', '-',
'0', '.', '=', '+',
];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Simple Calculator'),
backgroundColor: Theme.of(context).colorScheme.primary,
foregroundColor: Theme.of(context).colorScheme.onPrimary,
),
body: Column(
children: [
Expanded(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
Container(
// Answer
padding: EdgeInsets.all(10),
alignment: Alignment.centerRight,
child: SelectableText(
_answer,
style: Theme.of(context).textTheme.headlineLarge,
),
),
Container(
// User Input
padding: EdgeInsets.all(10),
alignment: Alignment.centerRight,
child: SelectableText(
_userInput,
style: Theme.of(context).textTheme.bodyLarge,
),),
],),
),
Expanded(
flex: 3,
child: GridView.builder(
itemCount: buttons.length,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 4,
mainAxisSpacing: 8.0,
crossAxisSpacing: 8.0,
childAspectRatio: 1.2,
),
itemBuilder: (BuildContext context, int index) {
switch (index) {
case 0:
// "C" button
return Buttons(
buttonStyle: ElevatedButton.styleFrom(
backgroundColor: Colors.red,
foregroundColor: Colors.white,
),
buttonString: buttons[index],
onTap: () {
setState(() {
_userInput = "";
});
},
);
case 1:
// "±" button
return Buttons(
buttonStyle: ElevatedButton.styleFrom(
backgroundColor: Colors.orange,
foregroundColor: Colors.white,
),
buttonString: buttons[index],
onTap: () {
setState(() {
if (_userInput == "" || _userInput[0] != "-") {
_userInput = "-$_userInput";
} else {
_userInput = _userInput.substring(1);
}
});
},
);
case var x when [2, 7, 11, 15, 19].contains(x):
// Operator buttons
return Buttons(
buttonStyle: ElevatedButton.styleFrom(
backgroundColor: Colors.orange,
foregroundColor: Colors.white,
),
buttonString: buttons[index],
onTap: () {
setState(() {
_userInput += buttons[index];
});
},
);
case 3:
// "DEL" button
return Buttons(
buttonStyle: ElevatedButton.styleFrom(
backgroundColor: Colors.red,
foregroundColor: Colors.white,
),
buttonString: buttons[index],
onTap: () {
setState(() {
_userInput =
_userInput.substring(0, _userInput.length - 1);
});
},
);
case 18:
// "=" button
return Buttons(
buttonStyle: ElevatedButton.styleFrom(
backgroundColor:
Theme.of(context).colorScheme.primary,
foregroundColor:
Theme.of(context).colorScheme.onPrimary,
),
buttonString: buttons[index],
onTap: () {
setState(() {
_equalPressed();
});
});
default:
// Number buttons
return Buttons(
buttonString: buttons[index],
onTap: () {
setState(() {
_userInput += buttons[index];
});
},);}},
),),],
),);}
// Calculate expression
void _equalPressed() {
try {
_answer = Parser()
.parse(_userInput)
.evaluate(EvaluationType.REAL, ContextModel())
.toString();
} catch (e) {
_answer = "Error";
}
}
}
class Buttons extends StatelessWidget {
final ButtonStyle? buttonStyle;
final String buttonString;
final void Function() onTap;
const Buttons({
super.key,
this.buttonStyle,
required this.buttonString,
required this.onTap,
});
@override
Widget build(BuildContext context) {
return ElevatedButton(
onPressed: onTap,
style: buttonStyle,
child: Text(
buttonString,
style: TextStyle(fontSize: 20),
),);
}
}
|
