How to add basic functionalities in calculator app? like addition, subtraction - flutter

Question

Can someone please help me with adding functionalities to my calculator app? Well, I have done everything in it the only thing remaining is to add calculations operation. I am a bit confused about how to make calculations operation work when the user inputs something please help me out! This is going to be my first app... code is given below
import 'package:calculator/constants/constants.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.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: 'Calculator',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
debugShowCheckedModeBanner: false,
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var question = "0";
var answer1 = "0";
var result = "";
/* String _privateOutput = "0"; */
/* double num1 = 0.0;
double num2 = 0.0;
String task = ""; */
Widget calculatorButton(String numberText) {
return Expanded(
child: MaterialButton(
onPressed: () {
setState(() {
if (question == "0") {
question = numberText;
} else {
question += numberText;
}
});
},
padding: EdgeInsets.all(24),
child: Text(
numberText,
style: kCalculatorStyle,
),
),
);
}
Widget calculatorButtonSymbols(String text) {
return Expanded(
child: MaterialButton(
onPressed: () {
setState(() {
if (text == "÷" || text == "×" || text == "+" || text == "-") {
} else if (text == "=") {}
});
},
padding: EdgeInsets.all(24),
child: Text(
text,
style: kCalculatorStyleSymbols,
),
),
);
}
Widget calculatorButtonTopSymbols(String text) {
return Expanded(
child: MaterialButton(
onPressed: () {
setState(() {
if (text == "AC") {
question = "0";
} else if (text == "±" || text == "%") {
question += text;
}
});
},
padding: EdgeInsets.all(24),
child: Text(
text,
style: kCalculatorStyleSymbols1,
),
),
);
}
Widget calculatorResetButton(IconData icon) {
return Expanded(
child: MaterialButton(
onPressed: () {
setState(() {
if (icon == Icons.arrow_back) {
question = question.substring(0, question.length - 1);
}
if (question == "") {
question = "0";
}
});
},
padding: EdgeInsets.all(24),
child: Icon(
icon,
size: 30,
),
),
);
}
#override
Widget build(BuildContext context) {
SystemChrome.setSystemUIOverlayStyle(
SystemUiOverlayStyle(
statusBarColor: Colors.transparent,
systemNavigationBarColor: Colors.transparent,
statusBarIconBrightness: Brightness.dark,
systemNavigationBarIconBrightness: Brightness.dark,
),
);
return Scaffold(
backgroundColor: Colors.white,
body: Container(
child: Column(
children: [
SafeArea(
child: Container(
alignment: Alignment.centerRight,
padding: EdgeInsets.all(20),
child: Text(
question,
style: kCalculatorStyle,
),
),
),
Expanded(child: Divider()),
Column(
children: [
Row(
children: [
calculatorButtonTopSymbols('AC'),
calculatorButtonTopSymbols('±'),
calculatorButtonTopSymbols('%'),
calculatorButtonSymbols('÷'),
],
),
Row(
children: [
calculatorButton('7'),
calculatorButton('8'),
calculatorButton('9'),
calculatorButtonSymbols('×'),
],
),
Row(
children: [
calculatorButton('4'),
calculatorButton('5'),
calculatorButton('6'),
calculatorButtonSymbols('-'),
],
),
Row(
children: [
calculatorButton('1'),
calculatorButton('2'),
calculatorButton('3'),
calculatorButtonSymbols('+'),
],
),
Row(
children: [
calculatorResetButton(Icons.arrow_back),
calculatorButton('0'),
calculatorButton('.'),
calculatorButtonSymbols('='),
],
),
],
),
],
),
),
);
}
}

Answer 1

Check Out this Link . You can get Idea From Here .