颤振，从函数读取多个值 [英] Flutter, reading multiple values from function
本文介绍了颤振，从函数读取多个值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
这是几天前我遇到的一个有关我的第一个Flutter应用程序的问题的跟进. 遵循PRO的建议，我更改了代码，以实现所需的功能. 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. 我只能显示我想要bij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
This is a followup of a question I had a couple off days ago about my first flutter app. Following advice from PRO I changed my code so that it did what I wanted. The only problem is that from the function I get only 1 value. Pro advised to make a list, which worked in the function like it should. Only how to get these values in a textfield is not clear to me. I can only show what I want bij sending the full code. Later I want to build on the same principal with more outcome values. I use value.toString() as well as value[1].toString(). The first gives me the first value, the second only a caracter. I hope someone can help
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 " '$spo');
List<double> valueList = List<double>();
valueList.add(spev);
valueList.add(spo);
print(valueList);
return valueList;
}
推荐答案
@Pim，您的代码中几乎没有错误，
@Pim, there are few errors in your code,
- 您正在显式调用小部件构建中的列表项，此处您还没有该值
- 您正在使用
value = getValue(kapController.text, buizenController.text, diamController.text).toString();将列表转换为字符串，不确定为什么要这样做，但这不正确.
- you are explicitly calling list item on widget build, here you don't have the value yet
- you are converting list into string with
value = getValue(kapController.text, buizenController.text, diamController.text).toString();, not sure why you're doing this but this in not correct.
尝试在小部件构建中为textFields分配空值，然后在按下按钮时分配实际值，最后像这样刷新状态，
Try assigning empty value to your textFields on widget build and then assign actual value on button press and finally refresh the state like so,
class Buis extends StatefulWidget {
@override
BuisState createState() => BuisState();
}
class BuisState extends State<Buis> {
var kap2 = '';
var buizen2 = '';
var diam2 = '';
var spev = '';
var spo = '';
var value;
var firstValue = '';
var secondValue = '';
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
TextEditingController kapController = TextEditingController();
TextEditingController buizenController = TextEditingController();
TextEditingController diamController = TextEditingController();
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Center(
child: Text("Specifiek buis vermogen"),
),
),
body: Center(
child: Container(
child: SingleChildScrollView(
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
SizedBox(height: 20),
// Input kap breedte
Container(
width: 170,
height: 30,
child: TextFormField(
controller: kapController,
keyboardType: TextInputType.number,
style: TextStyle(fontWeight: FontWeight.bold),
decoration: InputDecoration(
contentPadding:
EdgeInsets.symmetric(vertical: 5, horizontal: 8),
labelText: "Kap breedte (mtr)",
hintText: "$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;
}
这篇关于颤振，从函数读取多个值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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