如何在计算器应用程序中添加基本功能？比如加法减法

Question

有人可以帮我向我的计算器应用程序添加功能吗？好吧，我已经完成了其中的所有事情，唯一剩下的就是添加计算操作。当用户输入某些内容时，我对如何使计算操作工作感到有些困惑，请帮助我！这将是我的第一个应用程序...代码如下

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

看看这个Convert several YAML files to CSV。你可以从这里得到想法。