英文:
Global variable or passing the value of a variable to another screen
问题
我明白你的问题。你想要将在 "MyHomePage" 类中的 "bal" 变量的值传递到 "PageResult" 类中。以下是两种可能的解决方案：
解决方案1：通过构造函数传递数据
在 "PageResult" 类中创建一个构造函数，用于接收 "bal" 变量的值。然后，在 "MyHomePage" 类中创建 "PageResult" 类的实例时，将 "bal" 的值传递给构造函数。这是一个示例：
在 "PageResult" 类中：
class PageResult extends StatefulWidget {
final int bal; // 在构造函数中接收bal的值
PageResult(this.bal);
@override
MyWidgetState createState() => MyWidgetState();
}
class MyWidgetState extends State<PageResult> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Test Result"),
),
body: Text('bal的值: ${widget.bal}'), // 使用widget.bal来访问bal的值
);
}
}
在 "MyHomePage" 类中：
ElevatedButton(
onPressed: () {
QuestionsList.shared.nextQuestion();
// 其他代码...
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => PageResult(bal), // 通过构造函数传递bal的值
),
);
},
child: Text('NEXT'),
);
解决方案2：使用全局变量
你也可以使用全局变量来存储 "bal" 的值，以便在不同类之间共享。在Dart中，你可以使用全局变量或全局状态管理库来实现这一点，例如Provider、GetX等。这里提供一个全局变量的示例：
在一个单独的Dart文件（例如globals.dart）中创建一个全局变量：
int bal = 0;
然后，在 "MyHomePage" 类和 "PageResult" 类中都导入这个Dart文件，就可以访问和更新全局变量 "bal"。
请注意： 使用全局变量需要小心，因为它们可能会导致代码的维护性和可读性下降。最好的做法是使用状态管理库来处理应用程序的状态，以便更好地组织和维护代码。
英文:
I guess that the question is stupid, but for a day I can not solve this simplest problem.
In the class "MyHomePage" I have a variable "bal" which counts the correct answers.
import 'package:australia/qlist.dart';
import 'package:flutter/material.dart';
class MyHomePage extends StatefulWidget {
const MyHomePage({Key? key}) : super(key: key);
@override
State<MyHomePage> createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 1;
int bal = 0;
int bad = 0;
List<Color> colorsList = [
Colors.white,
Colors.white,
Colors.white,
Colors.white
];
List<String> answers = [];
@override
void initState() {
answers.addAll([
QuestionsList.shared.getCurrentQuestion().correctAnswer,
QuestionsList.shared.getCurrentQuestion().dis1,
QuestionsList.shared.getCurrentQuestion().dis2,
QuestionsList.shared.getCurrentQuestion().dis3,
]);
answers.shuffle();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text ("Exam test"),
),
body: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Column(
children: [
Padding(
padding: const EdgeInsets.all(8.0),
child: Row(
children: [
Text('$_counter'), Text('/20____'), Text('$bal'), Text('____'), Text('$bad'),
],
),
),
Center(
child: Text(QuestionsList.shared.getCurrentQuestion().question)),
],
),
Column(
children: [
Container(
width: double.infinity,
child: Card(
color: colorsList[0],
child: InkWell(
child: Container(
margin: const EdgeInsets.all(5.0),
child: Text(answers[0])),
onTap: () {
if (answers[0] ==
QuestionsList.shared.getCurrentQuestion().correctAnswer) {
colorsList[0] = Colors.green;
setState(() {
if (bad==0) {bal++;}
;
});
} else {
colorsList[0] = Colors.red;
setState(() {bad++;});
}
},
),
),),
Container(
width: double.infinity,
child: Card(
color: colorsList[1],
child: InkWell(
child: Container(
margin: const EdgeInsets.all(5.0),
child: Text(answers[1])),
onTap: () {
if (answers[1] ==
QuestionsList.shared.getCurrentQuestion().correctAnswer) {
colorsList[1] = Colors.green;
setState(() {
if (bad==0) {bal++;};
});
} else {
colorsList[1] = Colors.red;
setState(() {bad++;});
}
},
),
),),
Container(
width: double.infinity,
child: Card(
color: colorsList[2],
child: InkWell(
child: Container(
margin: const EdgeInsets.all(5.0),
child: Text(answers[2])),
onTap: () {
if (answers[2] ==
QuestionsList.shared.getCurrentQuestion().correctAnswer) {
colorsList[2] = Colors.green;
setState(() {
if (bad==0) {bal++;};
});
} else {
colorsList[2] = Colors.red;
setState(() {bad++;});
}
},
),
),),
Container(
width: double.infinity,
child: Card(
color: colorsList[3],
child: InkWell(
child: Container(
margin: const EdgeInsets.all(5.0),
child: Text(answers[3])),
onTap: () {
if (answers[3] ==
QuestionsList.shared.getCurrentQuestion().correctAnswer) {
colorsList[3] = Colors.green;
setState(() {
if (bad==0) {bal++;};
});
} else {
colorsList[3] = Colors.red;
setState(() {bad++;});
}
},
),
),),
ElevatedButton(
onPressed: () {
QuestionsList.shared.nextQuestion();
colorsList[0] = Colors.white;
colorsList[1] = Colors.white;
colorsList[2] = Colors.white;
colorsList[3] = Colors.white;
answers.clear();
answers.addAll([
QuestionsList.shared.getCurrentQuestion().correctAnswer,
QuestionsList.shared.getCurrentQuestion().dis1,
QuestionsList.shared.getCurrentQuestion().dis2,
QuestionsList.shared.getCurrentQuestion().dis3,
]);
answers.shuffle();
setState(() {
_counter++; bad=0;
if (_counter==20) {Navigator.push(
context,
MaterialPageRoute(
builder: (context)
=> PageResult()
),
);}
});
},
child: Text('NEXT')),
ElevatedButton(
onPressed: () {
Navigator.pop(context);
},
child: Text('BACK')),
],
)
]));
}
}
And I need to transfer its value to the "PageResult" class.
class PageResult extends StatefulWidget {
createState() => new MyWidgetState();
}
class MyWidgetState extends State<PageResult> {
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text ("Test Result")
),
// body: Text('$bal'),
);
}
}
I understand that there are 2 solutions.
1. Pass data from class to class
2. Make the "bal" variable global.
But I can't find a solution in the manuals. Help please.
答案1
得分: 1
你可以通过PageResult小部件的参数化构造函数传递变量，并从State中使用引用widget.bal。
class PageResult extends StatefulWidget {
PageResult({required this.bal}) : super();
final int bal;
createState() => new MyWidgetState();
}
class MyWidgetState extends State<PageResult> {
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Test Result")
),
body: Center(
child: Text('${widget.bal}'),
)
);
}
}
在推送路由时使用：
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => PageResult(bal: bal)
)
);
英文:
You can pass the variable with a parameterised constructor of PageResult widget. And use with the reference widget.bal from State
class PageResult extends StatefulWidget {
PageResult({required this.bal}) : super() ;
final int bal;
createState() => new MyWidgetState();
}
class MyWidgetState extends State<PageResult> {
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text ("Test Result")
),
body: Center(
child: Text('${widget.bal}'),
)
);
}
}
And while pushing the route
Navigator.push(
context,
MaterialPageRoute(
builder: (context)
=> PageResult(bal: bal)
),
);
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