Flutter 无效值：有效值范围为空：0
我是颤振初学者，我创建了一个颤振应用程序来显示一些来自互联网的数据，我有一个错误，上面写着Flutter 无效值：有效值范围为空：0,flutter,dart,Flutter,Dart,我是颤振初学者，我创建了一个颤振应用程序来显示一些来自互联网的数据，我有一个错误，上面写着RangeError（index）：无效值：有效值范围为空：0 持续几秒钟，然后出现此错误 以下是我尝试过的： import 'package:flutter/material.dart'; import 'package:footyappp/Key/Key.dart'; import 'package:footyappp/stats/player_goals.dart'; imp
RangeError（index）：无效值：有效值范围为空：0 import 'package:flutter/material.dart';
import 'package:footyappp/Key/Key.dart';
import 'package:footyappp/stats/player_goals.dart';
import 'package:footyappp/stats/teams_json.dart';
import 'package:footyappp/tables%20copy/league_board.dart';
import 'package:footyappp/stats/player_assists.dart';
import 'package:footyappp/stats/player_red_cards.dart';
import 'package:footyappp/stats/player_yellow_cards.dart';
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'assist_json.dart';
import 'goals_json.dart';
class Statss extends StatefulWidget {
@override
_StatssState createState() => _StatssState();
}
class _StatssState extends State<Statss> {
List<AssistsJson> topassists = [];
List<GoalsJson> topgoals = [];
List<TeamsJson> teams = [];
List<String> data = [];
List<Choices> menu = [];
String assister;
String assisterphoto;
String scorerphoto;
String assists;
String goals;
String scorer;
String teamgoals;
String teamname;
String teamphoto;
String teampoints;
Future<void> getScorers() async {
http.Response response = await http.get(
'https://v3.football.api-sports.io/players/topscorers?league=39&season=2020',
headers: {'x-rapidapi-key': ApiKey.key,
'x-rapidapi-host':'v3.football.api-sports.io'});
String body = response.body;
var data = jsonDecode(body);
List<dynamic> clubList = data['response'];
setState(() {
topgoals = clubList
.map((dynamic item) => GoalsJson.fromJson(item))
.toList();
goals = topgoals[0].statistics[0].goals.total.toString();
scorer = topgoals[0].player.name+" "+topgoals[0].player.firstname;
scorerphoto = topgoals[0].player.photo;
});
}
Future<void> getStandings() async {
http.Response response = await http.get(
'https://v3.football.api-sports.io/standings?league=39&season=2020',
headers: {'x-rapidapi-key': ApiKey.key,
'x-rapidapi-host':'v3.football.api-sports.io'});
String body = response.body;
var data = jsonDecode(body);
List<dynamic> clubList = data['response'];
setState(() {
teams = clubList
.map((dynamic item) => TeamsJson.fromJson(item))
.toList();
teamgoals = teams[0].league.standings[0][0].all.goals.goalsFor.toString()+" "+"Goals";
teamname = teams[0].league.standings[0][0].team.name.toString();
teamphoto = teams[0].league.standings[0][0].team.logo.toString();
teampoints = teams[0].league.standings[0][0].points.toString()+" "+"Pts";
});
}
Future<void> getAssisters() async {
http.Response response = await http.get(
'https://v3.football.api-sports.io/players/topassists?league=39&season=2020',
headers: {'x-rapidapi-key': ApiKey.key,
'x-rapidapi-host':'v3.football.api-sports.io'});
String body = response.body;
var data = jsonDecode(body);
List<dynamic> clubList = data['response'];
setState(() {
topassists = clubList
.map((dynamic item) => AssistsJson.fromJson(item))
.toList();
assists = topassists[0].statistics[0].goals.assists.toString();
assister = topassists[0].player.name+" "+topassists[0].player.firstname;
assisterphoto = topassists[0].player.photo;
});
}
@override
void initState() {
super.initState();
getScorers();
getAssisters();
getStandings();
}
List<String> images = [
"Assets/tt.jpg",
"Assets/qatarairways.jpg",
"Assets/LOGO_Danao.jpg",
"Assets/delice.jpg"
];
@override
Widget build(BuildContext context) {
if(topgoals.isNotEmpty && topassists.isNotEmpty){ this.menu = [
Choices("Top Scorer: ", goals.toString(), topgoals[0].player.name,topgoals[0].player.photo.toString()),
Choices("Top Assister: ", assists.toString(), topassists[0].player.name,topassists[0].player.photo.toString()),
Choices("Top Team Goals ", teamgoals.toString(), "",teamphoto.toString()),
Choices("1 st Team ", teampoints.toString(), "",teamphoto.toString()),
];}
return teams.isEmpty || topassists.isEmpty || topgoals.isEmpty
? Container(
color: Colors.white,
child: Center(
child: CircularProgressIndicator(
valueColor: AlwaysStoppedAnimation<Color>(
Color(0xFFe70066),
),
),
),
)
: Scaffold(
appBar: AppBar(
title: Text("Stats"),
backgroundColor: Colors.blue[300],
elevation: 0.0,
),
body: Container(
decoration: BoxDecoration(
gradient: LinearGradient(
begin: Alignment.centerLeft,
end: Alignment.centerRight,
colors: [Colors.purple, Colors.blue])),
child: ListView(
children: [
SizedBox(
height: 20,
),
Container(
margin: EdgeInsets.fromLTRB(10, 0, 0, 0),
child: Text(
"Statistiques",
style: TextStyle(
fontSize: 25,
fontWeight: FontWeight.w900,
color: Colors.white),
),
),
SizedBox(
height: 30,
),
Container(
padding: EdgeInsets.all(12.0),
child: GridView.builder(
shrinkWrap: true,
itemCount: menu.length,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 2,
crossAxisSpacing: 1.0,
mainAxisSpacing: 1.0),
itemBuilder: (BuildContext context, int index) {
return Card(
color: Colors.black,
elevation: 4.0,
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(10.0),
),
child: Container(
//padding: EdgeInsets.all(16.0),
child:
Column(
children: <Widget>[
Container(
padding: EdgeInsets.fromLTRB(30, 10, 30, 10),
height: 100,
width: 100,
decoration: BoxDecoration(
shape: BoxShape.circle,
image: DecorationImage(
image: NetworkImage(menu[index].image),
fit: BoxFit.fill
),
),
),
Container(
padding: EdgeInsets.all(7.0),
width: double.infinity,
child:
Center(
child: Text(menu[index].title+" "+menu[index].name,style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.w900,
color: Colors.white),),
)
),
Container(
padding: EdgeInsets.all(7.0),
width: double.infinity,
child: Center(
child: Text(menu[index].record, style: TextStyle(
fontSize: 25,
fontWeight: FontWeight.w900,
color: Colors.white),),
),
),
],
),
),
);
},
),
),
Container(
margin: EdgeInsets.fromLTRB(15, 30, 15, 0),
child: Column(
children: [
SizedBox(
height: 1,
),
ButtonTheme(
minWidth: double.infinity,
height: 40,
child: RaisedButton(
child: Align(
child: Text(
"Top Scorers",
style: TextStyle(fontSize: 17),
textAlign: TextAlign.right,
),
alignment: Alignment.centerLeft,
),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Scorers()),
);
},
color: Colors.grey.shade300,
textColor: Colors.black,
padding: EdgeInsets.fromLTRB(15, 8, 8, 8),
splashColor: Colors.green,
shape: RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0))),
),
SizedBox(
height: 1,
),
ButtonTheme(
minWidth: double.infinity,
height: 40,
child: RaisedButton(
child: Align(
child: Text(
"Top Assists",
style: TextStyle(fontSize: 17),
textAlign: TextAlign.right,
),
alignment: Alignment.centerLeft,
),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Assists()),
);
},
color: Colors.grey.shade300,
textColor: Colors.black,
padding: EdgeInsets.fromLTRB(15, 8, 8, 8),
splashColor: Colors.green,
shape: RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0))),
),
SizedBox(
height: 1,
),
ButtonTheme(
minWidth: double.infinity,
height: 40,
child: RaisedButton(
child: Align(
child: Text(
"Yellow Cards",
style: TextStyle(fontSize: 17),
textAlign: TextAlign.right,
),
alignment: Alignment.centerLeft,
),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => YellowCards()),
);
},
color: Colors.grey.shade300,
textColor: Colors.black,
padding: EdgeInsets.fromLTRB(15, 8, 8, 8),
splashColor: Colors.green,
shape: RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0))),
),
SizedBox(
height: 1,
),
ButtonTheme(
minWidth: double.infinity,
height: 40,
child: RaisedButton(
child: Align(
child: Text(
"Red Cards",
style: TextStyle(fontSize: 17),
textAlign: TextAlign.right,
),
alignment: Alignment.centerLeft,
),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => RedCards()),
);
},
color: Colors.grey.shade300,
textColor: Colors.black,
padding: EdgeInsets.fromLTRB(15, 8, 8, 8),
splashColor: Colors.green,
shape: RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0))),
),
SizedBox(
height: 1,
),
ButtonTheme(
minWidth: double.infinity,
height: 40,
child: RaisedButton(
child: Align(
child: Text(
"Team Stats",
style: TextStyle(fontSize: 17),
textAlign: TextAlign.right,
),
alignment: Alignment.centerLeft,
),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => LeagueBoard()),
);
},
color: Colors.grey.shade300,
textColor: Colors.black,
padding: EdgeInsets.fromLTRB(15, 8, 8, 8),
splashColor: Colors.green,
shape: RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0))),
),
SizedBox(
height: 30,
)
],
),
),
Container(
padding: EdgeInsets.all(12.0),
child: GridView.builder(
shrinkWrap: true,
itemCount: images.length,
gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
crossAxisCount: 2,
crossAxisSpacing: 4.0,
mainAxisSpacing: 4.0),
itemBuilder: (BuildContext context, int index) {
return Image.asset(images[index]);
},
),
),
SizedBox(
height: 30,
)
],
),
));
}
}
class Choices {
String title;
String record;
String name;
String image;
Choices(this.title,this.record,this.name,this.image);
}
导入“包装：颤振/材料.省道”；
导入“包：footyappp/Key/Key.dart”；
导入“包：footyappp/stats/player_goals.dart”；
导入“package:footyappp/stats/teams_json.dart”；
导入“包装：footyappp/表格%20份/联盟板.dart”；
导入“套装：footyappp/stats/player_assesss.dart”；
导入“套装：footyappp/stats/player_red_cards.dart”；
导入“套装：footyappp/stats/player_yellow_cards.dart”；
导入“dart:convert”；
将“package:http/http.dart”导入为http；
导入“assist_json.dart”；
导入“goals_json.dart”；
类Statss扩展StatefulWidget{
@凌驾
_StatssState createState（）=>\u StatssState（）；
}
类_StatssState扩展状态{
名单
我正试图找出这个错误背后的原因并加以纠正。
为什么这个错误会出现几秒钟然后消失？
任何帮助都将不胜感激。这是暂时的，因为在给定的时刻，在构建方法中，您要求它查看索引[0]，这意味着您正在告诉Flatter此列表中至少有一个项目。它返回一个错误，表示没有此类有效索引，并显示红色屏幕，直到您的未来函数完成运行，并调用setState
，现在该索引中实际有项目，并且它不是空列表
要解决此问题，您可以在构建依赖于列表的小部件之前检查列表是否为空，如下所示：
myList.isEmpty ? CircularProgressIndicator() : WidgetThatDependsOnTheListNotBeingEMpty()
这也给您带来了一个问题：
List<Choices> menu = [
Choices("Top Scorer: ", goals.toString(), topgoals[0].player.name,topgoals[0].player.photo.toString()),
Choices("Top Assister: ", assists.toString(), topassists[0].player.name,topassists[0].player.photo.toString()),
Choices("Top Team Goals ", teamgoals.toString(), "",teamphoto.toString()),
Choices("1 st Team ", teampoints.toString(), "",teamphoto.toString()),
];
列表菜单=[
选项（“顶级得分手：”，goals.toString（），topgoals[0]。player.name，topgoals[0]。player.photo.toString（）），
选项（“Top Assister:”，assists.toString（），topassists[0]。player.name，topassists[0]。player.photo.toString（）），
选项（“顶级团队目标”、teamgoals.toString（）、“”、teamphoto.toString（）），
选项（“第一团队”，teampoints.toString（），”，teamphoto.toString（）），
];
出于上述相同原因，您可以将其更改为：
if(topgoals.isNotEmpty && topassists.isNotEmpty) List<Choices> menu = [
Choices("Top Scorer: ", goals.toString(), topgoals[0].player.name,topgoals[0].player.photo.toString()),
Choices("Top Assister: ", assists.toString(), topassists[0].player.name,topassists[0].player.photo.toString()),
Choices("Top Team Goals ", teamgoals.toString(), "",teamphoto.toString()),
Choices("1 st Team ", teampoints.toString(), "",teamphoto.toString()),
];
if（topgoals.isNotEmpty&&topassists.isNotEmpty）列表菜单=[
选项（“顶级得分手：”，goals.toString（），topgoals[0]。player.name，topgoals[0]。player.photo.toString（）），
选项（“Top Assister:”，assists.toString（），topassists[0]。player.name，topassists[0]。player.photo.toString（）），
选项（“顶级团队目标”、teamgoals.toString（）、“”、teamphoto.toString（）），
选项（“第一团队”，teampoints.toString（），”，teamphoto.toString（）），
];
这是暂时发生的，因为在给定的时刻，在构建方法中，您要求它查看索引[0]，这意味着您正在告诉Flatter此列表中至少有一个项目。它返回一个错误，表示没有此类有效索引，并显示红色屏幕，直到您的未来函数完成运行，并调用setState
，现在该索引中实际有项目，并且它不是空列表
要解决此问题，您可以在构建依赖于列表的小部件之前检查列表是否为空，如下所示：
myList.isEmpty ? CircularProgressIndicator() : WidgetThatDependsOnTheListNotBeingEMpty()
这也给您带来了一个问题：
List<Choices> menu = [
Choices("Top Scorer: ", goals.toString(), topgoals[0].player.name,topgoals[0].player.photo.toString()),
Choices("Top Assister: ", assists.toString(), topassists[0].player.name,topassists[0].player.photo.toString()),
Choices("Top Team Goals ", teamgoals.toString(), "",teamphoto.toString()),
Choices("1 st Team ", teampoints.toString(), "",teamphoto.toString()),
];
列表菜单=[
选项（“顶级得分手：”，goals.toString（），topgoals[0]。player.name，topgoals[0]。player.photo.toString（）），
选项（“Top Assister:”，assists.toString（），topassists[0]。player.name，topassists[0]。player.photo.toString（）），
选项（“顶级团队目标”、teamgoals.toString（）、“”、teamphoto.toString（）），
选项（“第一团队”，teampoints.toString（），”，teamphoto.toString（）），
];
出于上述相同原因，您可以将其更改为：
if(topgoals.isNotEmpty && topassists.isNotEmpty) List<Choices> menu = [
Choices("Top Scorer: ", goals.toString(), topgoals[0].player.name,topgoals[0].player.photo.toString()),
Choices("Top Assister: ", assists.toString(), topassists[0].player.name,topassists[0].player.photo.toString()),
Choices("Top Team Goals ", teamgoals.toString(), "",teamphoto.toString()),
Choices("1 st Team ", teampoints.toString(), "",teamphoto.toString()),
];
if（topgoals.isNotEmpty&&topassists.isNotEmpty）列表菜单=[
选项（“顶级得分手：”，goals.toString（），topgoals[0]。player.name，topgoals[0]。player.photo.toString（）），
选项（“Top Assister:”，assists.toString（），topassists[0]。player.name，topassists[0]。player.photo.toString（）），
选项（“顶级团队目标”、teamgoals.toString（）、“”、teamphoto.toString（）），
选项（“第一团队”，teampoints.toString（），”，teamphoto.toString（）），
];
您要构建小部件的任何位置，该位置取决于列表是否为空。这将防止错误屏幕或您的应用程序引发错误。因为如果此列表为空，它将构建加载微调器，而不是依赖于列表的小部件。您可以在任何位置使用此微调器，而不仅仅是在此代码中。并且myList
下面是一个示例n example name.Bro，你是认真的吗？这也是一个假的\example name，你用造成问题的实际小部件替换它！我在更新后编辑了你的帖子，现在检查。现在尝试代码，看看错误是否仍然发生。我也为你修复了它，现在检查。Youc ant useStatss（）
像这样。调试它。stackoverflow不是这样工作的。试着找出错误是什么，你最终会找到它。此外，每篇文章都应该包含一个问题，到目前为止，我们已经有三个问题了。任何你想构建小部件的地方，这取决于列表是否为空。这将防止错误屏幕或你的应用程序抛出错误。Bec因为如果这个列表是空的，它将构建一个加载微调器，而不是依赖于列表的小部件。你可以在任何地方使用它，而不仅仅是在这个代码中。还有myList
这里是一个示例名称。兄弟，你是认真的吗？这也是一个假的\示例名称，你用你的实际小部件替换它，这是造成问题的原因！我编辑了你的帖子更新后，现在检查。现在尝试代码，看看错误是否仍然发生