颤振，从函数读取多个值
这是几天前我对第一个Flutter应用提出的一个问题的跟进。 遵循PRO的建议，我更改了代码，以实现我想要的功能。 唯一的问题是，从函数中我只能得到1个值。 Pro建议您列出一个清单，该清单可以在应有的功能下工作。 我不清楚如何在文本字段中获取这些值。 我只能显示想要发送完整代码的内容。 稍后，我想基于具有更多结果值的同一主体。 我使用value.toString（）以及value [1] .toString（）。 第一个给我第一个值，第二个给我一个角色。 希望有人能帮忙
import 'package:flutter/material.dart';
void main() {
runApp(Buis());
}
class Buis extends StatefulWidget {
@override
BuisState createState() => BuisState();
}
class BuisState extends State<Buis> {
var kap2 = '';
var buizen2 = '';
var diam2 = '';
var spev = '';
var spo = '';
var value;
@override
Widget build(BuildContext context) {
TextEditingController kapController = TextEditingController(text: '9.60');
TextEditingController buizenController = TextEditingController(text: '12');
TextEditingController diamController = TextEditingController(text: '51');
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Center(
child: Text("Specifiek buis vermogen"),
),
),
body: Center(
child: Container(
child: SingleChildScrollView(
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
SizedBox(height: 20),
// Input kap breedte
Container(
width: 170,
height: 30,
child: TextFormField(
controller: kapController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Kap breedte (mtr)",
hintText: "$kap2",
fillColor: Colors.cyan[200],
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(40.0),
borderSide: BorderSide(),
),
),
),
),
SizedBox(height: 10),
// Input aantal buizen
Container(
width: 170,
height: 30,
child: TextFormField(
controller: buizenController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Aantal buizen",
hintText: "$buizen2",
fillColor: Colors.cyan[200],
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(40.0),
borderSide: BorderSide(),
),
),
),
),
SizedBox(height: 10),
// Input buis diameter
Container(
width: 170,
height: 30,
child: TextFormField(
controller: diamController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Buis diameter (mm)",
hintText: '$diam2',
fillColor: Colors.cyan[200],
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(40.0),
borderSide: BorderSide(),
),
),
),
),
SizedBox(height: 10),
// Uitkomsten
Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
SizedBox(height: 20),
// Berekenen knop
Center(
child: RaisedButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
side: BorderSide(color: Colors.red)),
onPressed: () {
value = getValue(kapController.text, buizenController.text, diamController.text).toString();
setState(() {});
},
color: Colors.blue,
textColor: Colors.white,
child: Text("Berekenen".toUpperCase(),
style: TextStyle(fontSize: 14)),
),
),
SizedBox(height: 20),
Text(
'Specifiek vermogen ',
style: TextStyle(
backgroundColor: Colors.white,
fontWeight: FontWeight.bold),
),
// Specifiek vermogen
Container(
alignment: Alignment(0, 0),
width: 80,
height: 30,
margin: const EdgeInsets.only(right: 5.0),
padding: const EdgeInsets.all(3.0),
decoration: BoxDecoration(
color: Colors.red[200],
borderRadius: BorderRadius.horizontal(
left: Radius.circular(40),
right: Radius.circular(40),
),
border: Border.all(width: 1.0),
),
child:Text(
value[2].toString(), //here I read the first outcome
style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.bold,
),
),
),
SizedBox(height: 10),
Text(
'Specifiek oppervlak ',
style: TextStyle(
backgroundColor: Colors.white,
fontWeight: FontWeight.bold),
),
// Specifiek oppervlak
Container(
alignment: Alignment(0, 0),
width: 80,
height: 30,
margin: const EdgeInsets.only(right: 5.0),
padding: const EdgeInsets.all(3.0),
decoration: BoxDecoration(
color: Colors.red[200],
borderRadius: BorderRadius.horizontal(
left: Radius.circular(40),
right: Radius.circular(40),
),
border: Border.all(width: 1.0),
),
child: Text(
value[3].toString(), // and here the second
style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.bold,
),
),
),
SizedBox(height: 20),
SizedBox(height: 60),
],
),
],
),
),
),
),
),
);
}
}
getValue(kap, buizen, diam) {
var kap1 = double.parse(kap);
var buizen1 = double.parse(buizen);
var diam1 = double.parse(diam);
var spev = 1.7 * (diam1 / 51) * (buizen1 / kap1);
spev = num.parse(spev.toStringAsFixed(2));
var spo = (buizen1 * diam1 * 0.1) / kap1;
spo = num.parse(spo.toStringAsFixed(2));
print("Spev is " '$spev');
print("Spo is " '$spo');
List<double> valueList = List<double>();
valueList.add(spev);
valueList.add(spo);
print(valueList);
return valueList;
}
2 个答案:
答案 0 :(得分：1)
@Pim，您的代码中几乎没有错误
- 您正在显式调用小部件构建中的列表项，此处您还没有值
- 您正在使用
value = getValue(kapController.text, buizenController.text, diamController.text).toString();将列表转换为字符串，不确定为什么要这样做，但这不正确。
尝试在小部件构建中为textFields分配空值，然后在按下按钮时分配实际值，最后像这样刷新状态，
class Buis extends StatefulWidget {
@override
BuisState createState() => BuisState();
}
class BuisState extends State<Buis> {
var kap2 = '';
var buizen2 = '';
var diam2 = '';
var spev = '';
var spo = '';
var value;
var firstValue = '';
var secondValue = '';
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
TextEditingController kapController = TextEditingController();
TextEditingController buizenController = TextEditingController();
TextEditingController diamController = TextEditingController();
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Center(
child: Text("Specifiek buis vermogen"),
),
),
body: Center(
child: Container(
child: SingleChildScrollView(
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
SizedBox(height: 20),
// Input kap breedte
Container(
width: 170,
height: 30,
child: TextFormField(
controller: kapController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Kap breedte (mtr)",
hintText: "$kap2",
fillColor: Colors.cyan[200],
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(40.0),
borderSide: BorderSide(),
),
),
),
),
SizedBox(height: 10),
// Input aantal buizen
Container(
width: 170,
height: 30,
child: TextFormField(
controller: buizenController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Aantal buizen",
hintText: "$buizen2",
fillColor: Colors.cyan[200],
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(40.0),
borderSide: BorderSide(),
),
),
),
),
SizedBox(height: 10),
// Input buis diameter
Container(
width: 170,
height: 30,
child: TextFormField(
controller: diamController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Buis diameter (mm)",
hintText: '$diam2',
fillColor: Colors.cyan[200],
filled: true,
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(40.0),
borderSide: BorderSide(),
),
),
),
),
SizedBox(height: 10),
// Uitkomsten
Column(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
SizedBox(height: 20),
// Berekenen knop
Center(
child: RaisedButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(18.0),
side: BorderSide(color: Colors.red)),
onPressed: () {
value = getValue(kapController.text, buizenController.text, diamController.text);
//Depending on how many value you will have;
firstValue = value[0].toString();
secondValue = value[1].toString();
setState(() {});
},
color: Colors.blue,
textColor: Colors.white,
child: Text("Berekenen".toUpperCase(),
style: TextStyle(fontSize: 14)),
),
),
SizedBox(height: 20),
Text(
'Specifiek vermogen ',
style: TextStyle(
backgroundColor: Colors.white,
fontWeight: FontWeight.bold),
),
// Specifiek vermogen
Container(
alignment: Alignment(0, 0),
width: 80,
height: 30,
margin: const EdgeInsets.only(right: 5.0),
padding: const EdgeInsets.all(3.0),
decoration: BoxDecoration(
color: Colors.red[200],
borderRadius: BorderRadius.horizontal(
left: Radius.circular(40),
right: Radius.circular(40),
),
border: Border.all(width: 1.0),
),
child:Text(
firstValue.toString(), //here I read the first outcome
style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.bold,
),
),
),
SizedBox(height: 10),
Text(
'Specifiek oppervlak ',
style: TextStyle(
backgroundColor: Colors.white,
fontWeight: FontWeight.bold),
),
// Specifiek oppervlak
Container(
alignment: Alignment(0, 0),
width: 80,
height: 30,
margin: const EdgeInsets.only(right: 5.0),
padding: const EdgeInsets.all(3.0),
decoration: BoxDecoration(
color: Colors.red[200],
borderRadius: BorderRadius.horizontal(
left: Radius.circular(40),
right: Radius.circular(40),
),
border: Border.all(width: 1.0),
),
child: Text(
secondValue.toString(), // and here the second
style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.bold,
),
),
),
SizedBox(height: 20),
SizedBox(height: 60),
],
),
],
),
),
),
),
),
);
}
}
getValue(kap, buizen, diam) {
var kap1 = double.parse(kap);
var buizen1 = double.parse(buizen);
var diam1 = double.parse(diam);
var spev = 1.7 * (diam1 / 51) * (buizen1 / kap1);
spev = num.parse(spev.toStringAsFixed(2));
var spo = (buizen1 * diam1 * 0.1) / kap1;
spo = num.parse(spo.toStringAsFixed(2));
print("Spev is " '$spev');
print("Spo is " '$spo');
List<double> valueList = List<double>();
valueList.add(spev);
valueList.add(spo);
print(valueList);
return valueList;
}
答案 1 :(得分：0)
当您将字符串称为string[1]时，是在要求字符串中的第二个字符。
设置value时，会将其设置为字符串。尝试从.toString()的末尾删除value = getValue(kapController.text, buizenController.text, diamController.text).toString();，这样value将成为一个列表，您可以获得该列表的第n个元素。
我还建议您在首次声明value时设置其类型。代替var value;使用List<double> value;
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