Flutter Calculator Homework

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  int firstNumber;
  int secondNumber;
  var result;

  TextEditingController firstTextEditingController;
  TextEditingController secondTextEditingController;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    firstTextEditingController = TextEditingController();
    secondTextEditingController = TextEditingController();
  }

  void changeFirstNumber(String str) {
    print(str);
    firstTextEditingController.text = str;
  }

  void changeSecondNumber(String str) {
    print(str);
    secondTextEditingController.text = str;
  }

  void plusClicked() {
    result = int.parse(firstTextEditingController.text) +
        int.parse(secondTextEditingController.text);
    setState(() {});
  }

  void subtractClicked() {
    result = int.parse(firstTextEditingController.text) -
        int.parse(secondTextEditingController.text);
    setState(() {});
  }

  void multiplyClicked() {
    result = int.parse(firstTextEditingController.text) *
        int.parse(secondTextEditingController.text);
    setState(() {});
  }

  void dividedClicked() {
    result = int.parse(firstTextEditingController.text) /
        int.parse(secondTextEditingController.text);
    setState(() {});
  }

  void percentClicked() {
    result = int.parse(firstTextEditingController.text) %
        int.parse(secondTextEditingController.text);
    setState(() {});
  }

  void clearText() {
    firstTextEditingController.text = '';
    secondTextEditingController.text = '';
    result = '';
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Calculator Homework',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Calculator Homework'),
        ),
        body: Center(
          child: Container(
            padding: EdgeInsets.all(30),
            child: Column(
              children: [
                // first input box
                TextField(
                  controller: firstTextEditingController,
                  keyboardType: TextInputType.number,
                  onSubmitted: changeFirstNumber,
                ),
                SizedBox(
                  height: 20,
                ),
                // second input box
                TextField(
                  controller: secondTextEditingController,
                  keyboardType: TextInputType.number,
                  onSubmitted: changeSecondNumber,
                ),
                SizedBox(
                  height: 20,
                ),
                //Result Text
                Text('Result : $result'),
                SizedBox(
                  height: 20,
                ),
                Row(
                  children: [
                    Expanded(
                      child: RaisedButton(
                        color: Colors.blue,
                        onPressed: plusClicked,
                        child: Text(
                          '+',
                          style: TextStyle(color: Colors.white, fontSize: 20),
                        ),
                      ),
                    ),
                    SizedBox(
                      width: 20,
                    ),
                    Expanded(
                      child: RaisedButton(
                        color: Colors.blue,
                        onPressed: subtractClicked,
                        child: Text(
                          '-',
                          style: TextStyle(color: Colors.white, fontSize: 20),
                        ),
                      ),
                    ),
                    SizedBox(
                      width: 20,
                    ),
                    Expanded(
                      child: RaisedButton(
                        color: Colors.blue,
                        onPressed: multiplyClicked,
                        child: Text(
                          '*',
                          style: TextStyle(color: Colors.white, fontSize: 20),
                        ),
                      ),
                    )
                  ],
                ),
                SizedBox(
                  height: 20,
                ),
                Row(
                  children: [
                    Expanded(
                      child: RaisedButton(
                        color: Colors.blue,
                        onPressed: dividedClicked,
                        child: Text(
                          '/',
                          style: TextStyle(color: Colors.white, fontSize: 20),
                        ),
                      ),
                    ),
                    SizedBox(
                      width: 20,
                    ),
                    Expanded(
                      child: RaisedButton(
                        color: Colors.blue,
                        onPressed: percentClicked,
                        child: Text(
                          '%',
                          style: TextStyle(color: Colors.white, fontSize: 20),
                        ),
                      ),
                    ),
                    SizedBox(
                      width: 20,
                    ),
                    Expanded(
                      child: RaisedButton(
                        color: Colors.green,
                        onPressed: clearText,
                        child: Text(
                          'Clear',
                          style: TextStyle(color: Colors.white, fontSize: 20),
                        ),
                      ),
                    )
                  ],
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}