如何在颤振中创建功能按钮?

Question

我是颤振的新手，我正在尝试创建一个功能计算器。我的布局是正确的。但是，由于某种原因，当我单击按钮并要求应用程序执行某些操作时，我无法更改 main.dart 的状态。我为我的按钮创建了一个单独的类，并使用按钮按钮 = 按钮((在 main.dart 中调用它们;

import 'package:flutter/material.dart';
import 'button.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Scaffold(
appBar: AppBar(
title: Center(
child: Text(
'CALCULATOR',
style: TextStyle(fontSize: 25.0),
),
),
),
body: ButtonsBuild(),
),
);
}
}
Button button = Button();
//We have now created a local variable to store the properties of Button into button. So we can now use its properties in main.dart
class ButtonsBuild extends StatefulWidget {
@override
_ButtonsBuildState createState() => _ButtonsBuildState();
}
class _ButtonsBuildState extends State<ButtonsBuild> {
Widget buildButton(String buttonText) {
return Padding(
padding: const EdgeInsets.all(7.4),
child: FlatButton(
onPressed: () {
setState(
() {
return button.buttonPressed(buttonText);
},
);
},
child: Text(
'$buttonText',
style: TextStyle(
fontSize: 30.0,
fontStyle: FontStyle.normal,
color: Colors.grey[900]),
),
),
);
}
@override
Widget build(BuildContext context) {
return Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(15.0),
child: Container(
child: Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Text(button.outPut
,
style: TextStyle(fontSize: 45.0),
)
],
),
),
),
Divider(
height: 15.0,
),
Column(
children: <Widget>[
Row(
children: <Widget>[
Container(
child: Column(
children: <Widget>[
Row(
//button.buildButton is created coz build button is a property of a separate class that belongs to Button
children: <Widget>[
buildButton('.'),
buildButton('/'),
buildButton('*'),
],
),
Row(
children: <Widget>[
buildButton('7'),
buildButton('8'),
buildButton('9'),
],
),
Row(
children: <Widget>[
buildButton('4'),
buildButton('5'),
buildButton('6'),
],
),
Row(
children: <Widget>[
buildButton('1'),
buildButton('2'),
buildButton('3'),
],
),
Container(
width: 300,
child: Row(
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
Expanded(flex:2,
child: buildButton('0'),
),
Expanded(child: buildButton('=')),
],
),
)
],
),
),
Container(
height: 320,
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
buildButton('-'),
Expanded(flex: 2,
child: buildButton('+'),
),
Expanded(
child: buildButton('C'),
),
],
),
)
],
)
],
)
],
);
}
}

现在下面的代码是我为我的按钮创建一个单独的类的地方 导入"包装：颤振/材料.dart";

class Button {
String buttonText;
String outPut = '0';
double num1 = 0.0;
double num2 = 0.0;
String operand = '';
String outPutText = '0';
Button({
String buttonText,
String outPut = '0',
double num1 = 0.0,
double num2 = 0.0,
String operand = '',
String outPutText = '0',
}) {
this.buttonText = buttonText;
this.outPut = outPut;
this.num1 = num1;
this.num2 = num2;
this.operand = operand;
this.outPut = outPutText;
}
buttonPressed(String buttonText) {
if (buttonText == 'C') {
num1 = 0.0;
num2 = 0.0;
operand = '';
outPutText = '0';
} else if (buttonText == '+' ||
buttonText == '-' ||
buttonText == '/' ||
buttonText == '*') {
num1 = double.parse(outPut);
operand = buttonText;
outPutText = '0';
} else if (buttonText == '.') {
if (outPutText.contains('.')) {
print('Already contains Decimal');
return;
} else {
outPutText = outPutText + buttonText;
}
} else if (buttonText == '=') {
num2 = double.parse(outPut);
if (operand == '+') {
outPutText = (num1 + num2).toString();
}
if (operand == '-') {
outPutText = (num1 - num2).toString();
}
if (operand == '/') {
outPutText = (num1 / num2).toString();
}
if (operand == '*') {
outPutText = (num1 * num2).toString();
}
num1 = 00;
num2 = 00;
operand = '';
} else {
outPutText = outPutText = buttonText;
}
print(outPutText);
// setState(() {
//       outPut = double.parse(outPutText).toStringAsFixed(2);});
}

}

Answer 1

你的代码不接受 setState((({}(; 因为现在，它是一个无状态的小部件。将其更改为有状态小部件可能会解决问题。