当我运行范围错误索引时，我得到了一个错误:不包括范围0.34

Question

下面是我的主要部分：

import 'package:flutter/material.dart';
import './questions.dart';
import './answers.dart';
/*void main(){   runApp(MyApp()); }*/
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return MyAppState();
}
}
class MyAppState extends State<MyApp> {
var questionIndex = 0;
void ansQuestion() {
setState(() {
questionIndex = questionIndex + 1;
});
print(questionIndex);
}
@override
Widget build(BuildContext context) {
var questions = [
{
'question': 'whats youre favourite color',
'answers': ['red', 'blue', 'green', 'orange']
},
{
'question': 'how did you sleep',
'answers': ['well', 'good', 'badly', 'very badly']
},
{
'question': 'how high can you jump',
'answers': ['high', 'low', 'very high', 'so low']
},
{
'question': 'are you silly',
'answers': ['kinda', 'no', 'yes', 'i dont know']
},
];
return MaterialApp(
home: Scaffold(
appBar: AppBar(title: const Text('Simple Quiz App')),
body: Column(
children: [
Question(
questions[questionIndex]['question'] as String,
),
...(questions[questionIndex]['answers'] as List<String>)
.map((answer) {
return Answers(ansQuestion, answer);
}).toList()
],
),
),
);
}
}

问题。dart:

import 'package:flutter/material.dart';
class Question extends StatelessWidget {
@override
final String myQuestions;
Question(this.myQuestions);
Widget build(BuildContext context) {
return Container(
width: double.infinity,
margin: EdgeInsets.all(10),
child: Text(myQuestions,
style: TextStyle(fontSize: 20), textAlign: TextAlign.center),
);
}
}

和答案。dart:

import 'package:flutter/material.dart';
class Answers extends StatelessWidget {
final Function selectHandler;
final String answerText;
Answers(this.selectHandler, this.answerText);
@override
Widget build(BuildContext context) {
return Container(
width: double.infinity,
child: ElevatedButton(
child: Text(answerText),
onPressed: selectHandler(),
),
);
}
}

Answer 1

U需要控制您可以使用的最大索引。

像这样：

final int maxIdx = questions.length - 1;
questionIndex++;
If (questionIndex < maxIdx){
//Do something
} else {
// Do something
}