Calculator project by flutter

 Calculator project by flutter

Project's video clip

Free source code here

main.dart

import 'package:flutter/material.dart';

import 'home_page.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: HomePage(),
    );
  }
}

home_page.dart

import 'package:flutter/material.dart';
import 'package:math_expressions/math_expressions.dart';

import 'buttons.dart';

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  var userQuestion = '';
  var userAnswer = '';

  isOperator(String x) {
    if (x == '%' || x == '/' || x == 'X' || x == '-' || x == '+' || x == '=') {
      return true;
    }
    return false;
  }

  void calculation() {
    String finalQuestion = userQuestion.replaceAll('X', '*');

    Parser p = Parser();
    Expression exp = p.parse(finalQuestion);
    ContextModel cm = ContextModel();
    double eval = exp.evaluate(EvaluationType.REAL, cm);

    userAnswer = eval.toInt().toString();
  }

  final List<String> buttons = [
    'C',
    'DEL',
    '%',
    '/',
    '9',
    '8',
    '7',
    'X',
    '6',
    '5',
    '4',
    '-',
    '3',
    '2',
    '1',
    '+',
    '0',
    '.',
    'ANS',
    '=',
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.deepPurple[100],
      body: Column(
        children: [
          Expanded(
              child: Column(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: [
              Container(
                padding: const EdgeInsets.only(top: 50.0, left: 20),
                alignment: Alignment.centerLeft,
                child: Text(
                  userQuestion,
                  style: const TextStyle(fontSize: 24),
                ),
              ),
              Container(
                  padding: const EdgeInsets.only(top: 60.0, right: 20),
                  alignment: Alignment.centerRight,
                  child: Text(
                    userAnswer,
                    style: const TextStyle(fontSize: 24),
                  )),
            ],
          )),
          Expanded(
              flex: 3,
              child: GridView.builder(
                physics: const NeverScrollableScrollPhysics(),
                gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                    crossAxisCount: 4),
                itemCount: buttons.length,
                itemBuilder: (BuildContext context, int index) {
                  // Clear button
                  if (index == 0) {
                    return MyButton(
                      buttonTap: () {
                        setState(() {
                          if (userQuestion.isNotEmpty ||
                              userAnswer.isNotEmpty) {
                            userQuestion = '';
                            userAnswer = '';
                          }
                        });
                      },
                      buttonColor: Colors.green,
                      textColor: Colors.white,
                      buttonText: buttons[index],
                    );
                  }
                  // del button
                  else if (index == 1) {
                    return MyButton(
                      buttonTap: () {
                        setState(() {
                          if (userQuestion.isNotEmpty) {
                            userQuestion = userQuestion.substring(
                                0, userQuestion.length - 1);
                          }
                        });
                      },
                      buttonColor: Colors.red,
                      textColor: Colors.white,
                      buttonText: buttons[index],
                    );
                  }
                  // Equal button
                  else if (index == buttons.length - 1) {
                    return MyButton(
                      buttonTap: () {
                        setState(() {
                          calculation();
                        });
                      },
                      buttonColor: Colors.deepPurple,
                      textColor: Colors.white,
                      buttonText: buttons[index],
                    );
                  }
                  // Others button
                  else {
                    return MyButton(
                      buttonTap: () {
                        setState(() {
                          userQuestion += buttons[index];
                        });
                      },
                      buttonColor: isOperator(buttons[index])
                          ? Colors.deepPurple
                          : Colors.deepPurple[50],
                      textColor: isOperator(buttons[index])
                          ? Colors.white
                          : Colors.deepPurple,
                      buttonText: buttons[index],
                    );
                  }
                },
              )),
        ],
      ),
    );
  }
}

buttons.dart

import 'package:flutter/material.dart';

class MyButton extends StatelessWidget {
  final buttonColor;
  final textColor;
  final String buttonText;
  final buttonTap;

  const MyButton(
      {Key? key,
      this.buttonColor,
      this.textColor,
      required this.buttonText,
      this.buttonTap})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: buttonTap,
      child: Padding(
        padding: const EdgeInsets.all(4.0),
        child: ClipRRect(
          borderRadius: BorderRadius.circular(30),
          child: Container(
            color: buttonColor,
            child: Center(
              child: Text(
                buttonText,
                style: TextStyle(color: textColor, fontSize: 24),
              ),
            ),
          ),
        ),
      ),
    );
  }
}