【发布时间】：2021-11-13 01:31:30
【问题描述】：
我想构建一个如下图所示的测验应用程序
但我得到了那个错误，那是因为组值的索引。 我是颤振和编码的新手，所以请帮助我。 我不知道如何解决它。
class _ReadingPage2State extends State<ReadingPage2> {
bool _isloading = false;
List<int> groupValue = [];
List<List<int>> value = [];
int questionId;
Future<Response> loadQuestion() async {
final url = Network().link('/exercise/1/questions');
SharedPreferences localStorage = await SharedPreferences.getInstance();
final token = jsonDecode(localStorage.getString('token'));
http.Response response = await http.get(Uri.parse(url), headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization': 'Bearer $token',
});
if (response.statusCode == 200) {
var jsonResponce = response.body;
Response res = Response.fromJson(json.decode(jsonResponce));
return res;
} else
throw Exception('Failed to load Question');
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
appBar: AppBar(
title: Text("Set 1"),
backgroundColor: Colors.orange,
),
body: SafeArea(
child: Column(
children: [
Expanded(
child: FutureBuilder<Response>(
future: loadQuestion(),
builder: (context, AsyncSnapshot<Response> snapshot) {
if (snapshot.hasData) {
List<Result> list = snapshot.data.result;
return ListView.builder(
itemCount: list.length + 1,
itemBuilder: (context, index) => index < list.length
?
Column(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
mainAxisSize: MainAxisSize.max,
children: [
Container(
child: Column(
children: <Widget>[
Text(
snapshot
.data.result[index].questionText,
textAlign: TextAlign.center,
style: TextStyle(
fontSize: 20.0,
fontWeight: FontWeight.w600),
),
Container(
width: 150,
child: Row(
children: <Widget>[
Radio(
value: snapshot
.data
.result[index]
.options[0]
.id,
groupValue: groupValue[index],
onChanged: (value) {
setState(() {
groupValue[index] = value;
print(groupValue[index]);
});
}),
Text(
snapshot.data.result[index]
.options[0].option,
style: TextStyle(fontSize: 20)),
],
),
),
Container(
width: 150,
child: Row(
children: <Widget>[
Radio(
value: snapshot
.data
.result[index]
.options[1]
.id,
groupValue: groupValue[index],
onChanged: (value) {
setState(() {
groupValue[index] = value;
print(groupValue[index]);
});
}),
Text(
snapshot.data.result[index]
.options[1].option,
style: TextStyle(fontSize: 20)),
],
),
),
SizedBox(height: 25),
],
),
),
],
)
: MaterialButton(
minWidth: double.infinity,
height: 40,
onPressed: () {
saveAnswer(questionId, groupValue[index]);
},
color: Color(0xFFFF9D00),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(50),
),
child: Text('Submit'),
),
);
} else if (snapshot.hasError) {
debugPrint("${snapshot.error}");
return Text("${snapshot.error}",
style: TextStyle(fontSize: 15));
}
return Center(child: CircularProgressIndicator());
},
),
),
],
),
),
);
}
如果我将默认值设置为组值，就可以了，并且可以显示问题。但我不想为其设置默认值。
【问题讨论】：
标签： flutter listview radio-button flutter-futurebuilder