如何在计算器应用程序颤振中添加功能

您在 calculatorButton 中的代码被反转：

          setState(() {
            output += numberText;
          });

通过这种方式，您将把 numberText 连接到 output。

很简单。试试这个代码。

import 'package:flutter/material.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(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then,without quitTing the app,try
        // changing the priMarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",// or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset BACk to zero; the application
        // is not restarted.
        priMarySwatch: Colors.blue,),home: MyHomePage(),debugShowcheckedModeBAnner: false,);
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String output = '0';

  /* String _privateOutput = "0"; */
  /* double num1 = 0.0;
  double num2 = 0.0;
  String task = ""; */

  Widget calculatorButton(String numberText) {
    return Expanded(
      child: MaterialButton(
        onPressed: () {
          setState(() {
            output= numberText;
          });
        },padding: EdgeInsets.all(24),child: Text(
          numberText,);
  }

  Widget calculatorButtonSymbols(String text) {
    return Expanded(
      child: MaterialButton(
        onPressed: () {},child: Text(
          text,);
  }

  Widget calculatorButtonTopSymbols(String text) {
    return Expanded(
      child: MaterialButton(
        onPressed: () {},);
  }

  Widget calculatorResetButton() {
    return Expanded(
      child: MaterialButton(
        onPressed: () {},child: Icon(
          Icons.refresh,size: 30,);
  }

  @override
  Widget build(BuildContext context) {
    
    return Scaffold(
      BACkgroundColor: Colors.white,body: Container(
        child: column(
          children: [
            SafeArea(
              child: Text(
                output,Expanded(child: Divider()),column(
              children: [
                Row(
                  children: [
                    calculatorButtonTopSymbols('AC'),calculatorButtonTopSymbols('+/-'),calculatorButtonTopSymbols('%'),calculatorButtonSymbols('/'),],Row(
                  children: [
                    calculatorButton('7'),calculatorButton('8'),calculatorButton('9'),calculatorButtonSymbols('x'),Row(
                  children: [
                    calculatorButton('4'),calculatorButton('5'),calculatorButton('6'),calculatorButtonSymbols('-'),Row(
                  children: [
                    calculatorButton('1'),calculatorButton('2'),calculatorButton('3'),calculatorButtonSymbols('+'),Row(
                  children: [
                    calculatorResetButton(),calculatorButton('0'),calculatorButton('.'),calculatorButtonSymbols('='),);
  }
}

你在setState()中错了应该是这样的，output是我们更新的状态numberText是一个参数

onPressed: () {
  setState(() {
     output= numberText;
  });
},

正如其他人回答的那样，您的作业是错误的，这是正确的版本：

onPressed: () {
  setState(() {
     output= numberText;
  });
},

但是，您需要考虑如何最好地处理不同按钮文本的不同逻辑。这是向每个按钮传递回调函数的方法的开始：

  void digitPressed(String digit) {
    String newOutput;
    if (digit != '.') {
      if (output == '0') {
        newOutput = digit;
      } else {
        newOutput = output + digit;
      }
    } else if (!output.contains('.')) {
      newOutput = output + digit;
    }

    setState(() {
      output = newOutput;
    });
  }

然后所有的数字按钮都调用这个回调：

  Widget calculatorButton(String numberText,Function digitPressed) {
    return Expanded(
      child: MaterialButton(
        onPressed: () {
          digitPressed(numberText);
        },

它们是通过回调创建的：

            Row(
              children: [
                calculatorButton('7',digitPressed),calculatorButton('8',calculatorButton('9',

到目前为止，我们对每个按钮都有相同的通用回调。当然，其他按钮需要不同的回调函数。

为了实现运算符，您需要记住运算符之前的先前输出。如果要实现运算符优先级，则需要一堆值。我相信你可以谷歌搜索计算器算法，祝你好运！