我要接受用户输入的建筑物高度的高度，因此我要求用户以h [space] h格式输入值，然后提取数字并将其放入高度列表，但是当我显示其中一个索引我得到上面的错误|| 导入'package：flutter / material.dart'; 导入'package：flutter / cupertino.dart';
class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
int buildings;
List<int> heights = [];
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
body: SingleChildScrollView(
child: Container(
width: MediaQuery.of(context).size.width,
height: 341,
decoration: BoxDecoration(
gradient: LinearGradient(colors: [
Color.fromRGBO(223, 39, 17, 0.98),
Color.fromRGBO(245, 160, 25, 0.98)
], begin: Alignment.topRight, end: Alignment.bottomLeft),
borderRadius: BorderRadius.only(
bottomLeft: Radius.circular(30),
bottomRight: Radius.circular(30)),
boxShadow: [
BoxShadow(
color: Colors.black12,
spreadRadius: 5,
blurRadius: 5,
offset: Offset(1, 2))
]),
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Column(
children: <Widget>[
Row(
children: <Widget>[
SizedBox(
width: 278,
),
CircleAvatar(
radius: 25,
backgroundColor: Colors.transparent,
backgroundImage: AssetImage("assets/icon2.png"))
],
),
Row(
children: <Widget>[
Text(
"How many Buildings?",
style: TextStyle(
fontSize: 24,
color: Colors.white,
fontWeight: FontWeight.bold,
//fontStyle: FontStyle.italic,
fontFamily: 'MuseoModerno',
),
),
],
),
Container(
width: 325,
height: 60,
child: TextFormField(
keyboardType: TextInputType.number,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(15)),
hintText: 'Enter Number of Buildings and press enter',
focusedBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Colors.white),
),
),
onFieldSubmitted: (String n) {
setState(() {
buildings = int.parse(n);
});
},
),
),
Row(
children: <Widget>[
Text(
"Enter the Heights",
style: TextStyle(
fontSize: 22,
color: Colors.white,
fontWeight: FontWeight.bold,
//fontStyle: FontStyle.italic,
fontFamily: 'MuseoModerno',
),
),
],
),
Container(
width: 325,
height: 60,
child: TextFormField(
keyboardType: TextInputType.number,
decoration: InputDecoration(
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(15)),
hintText:
'Enter heights in h[space]h[space]h[space]h... format',
focusedBorder: UnderlineInputBorder(
borderSide: BorderSide(color: Colors.white),
),
),
onFieldSubmitted: (String n) {
setState(() {
for (int i = 0; i <= buildings - 1; i++) {
if (i != buildings - 1) {
if (n.substring(i, i + 1) != " ") {
heights[i] = int.parse(n.substring(i, i + 1));
}
} else {
heights[i]=int.parse(n.substring(i-1,i));
}
}
});
},
),
),
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 1),
child: ButtonTheme(
height: 55,
minWidth: 65,
child: RaisedButton(
elevation: 3,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(30.0),
side: BorderSide(color: Colors.transparent)),
child: new Text(
"Initiate",
style: TextStyle(
color: Colors.white,
fontSize: 25,
fontFamily: "MuseoModerno",
fontWeight: FontWeight.bold),
),
color: Colors.black,
onPressed: () {
print(buildings);
print(heights[0]);
},
),
),
)
],
)
],
),
),
),
));
}
}
答案 0 :(得分：0)
您的身高列表为空，因此您不能使用它来访问元素
heights[i] = int.parse(n.substring(i, i + 1));
代替使用heights.add()将元素添加到列表