Flutter 如何启用按钮
在我的一个颤振应用程序页面中,我想首先禁用Flutter 如何启用按钮,flutter,button,disable,Flutter,Button,Disable,在我的一个颤振应用程序页面中,我想首先禁用next按钮。如果用户在文本字段中输入任何新值,我想启用next按钮。这是我的代码,但无论发生什么情况,next按钮都将保持禁用状态。当用户输入值时,如何启用next按钮 @覆盖 小部件构建(构建上下文){ bool btnenabled=错误; 返回脚手架( appBar:appBar( 背景颜色:Colors.red, 标题:文本(“地址”), ), 正文:专栏( 儿童:[ ..... TextFormField( 一旦更改:(newValue){
next
按钮。如果用户在文本字段中输入任何新值,我想启用next
按钮。这是我的代码,但无论发生什么情况,next
按钮都将保持禁用状态。当用户输入值时,如何启用next
按钮
@覆盖
小部件构建(构建上下文){
bool btnenabled=错误;
返回脚手架(
appBar:appBar(
背景颜色:Colors.red,
标题:文本(“地址”),
),
正文:专栏(
儿童:[
.....
TextFormField(
一旦更改:(newValue){
_currentaddress='$addressJSON'+newValue;
如果(newValue.length>0){
设置状态(){
btnenabled=真;
});
}
}),
文本按钮(
样式:TextButton.styleFrom(
背景色:颜色。蓝色[700],原色:颜色。白色),
子项:文本('next',
),
onPressed:btnenabled==true
?()=>Navigator.push(上下文,
MaterialPage路由(生成器:(上下文)=>Summary())
:null)
],
),
);
}
}
您可以复制粘贴运行下面的完整代码您可以移动
boolbtnenabled=false代码>超出小部件构建
从
Widget build(BuildContext context) {
bool btnenabled = false;
到
工作演示
完整代码
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
bool btnenabled = false;
String _currentaddress = "";
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.red,
title: Text('Address'),
),
body: Column(
children: <Widget>[
TextFormField(onChanged: (newValue) {
_currentaddress = 'addressJSON' + newValue;
if (newValue.length > 0) {
setState(() {
btnenabled = true;
});
}
}),
TextButton(
style: TextButton.styleFrom(
backgroundColor: Colors.blue[700], primary: Colors.white),
child: Text(
'next',
),
onPressed: btnenabled == true
? () => Navigator.push(context,
MaterialPageRoute(builder: (context) => Summary()))
: null)
],
),
);
}
}
class Summary extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Text("Summary");
}
}
导入“包装:颤振/材料.省道”;
void main(){
runApp(MyApp());
}
类MyApp扩展了无状态小部件{
@凌驾
小部件构建(构建上下文){
返回材料PP(
标题:“颤振演示”,
主题:主题数据(
主样本:颜色。蓝色,
),
主页:MyHomePage(标题:“颤振演示主页”),
);
}
}
类MyHomePage扩展StatefulWidget{
MyHomePage({Key,this.title}):超级(Key:Key);
最后的字符串标题;
@凌驾
_MyHomePageState createState()=>\u MyHomePageState();
}
类_MyHomePageState扩展状态{
bool btnenabled=错误;
字符串_currentaddress=“”;
@凌驾
小部件构建(构建上下文){
返回脚手架(
appBar:appBar(
背景颜色:Colors.red,
标题:文本(“地址”),
),
正文:专栏(
儿童:[
TextFormField(onChanged:(newValue){
_currentaddress='addressJSON'+newValue;
如果(newValue.length>0){
设置状态(){
btnenabled=真;
});
}
}),
文本按钮(
样式:TextButton.styleFrom(
背景色:颜色。蓝色[700],原色:颜色。白色),
子:文本(
“下一个”,
),
onPressed:btnenabled==true
?()=>Navigator.push(上下文,
MaterialPage路由(生成器:(上下文)=>Summary())
:null)
],
),
);
}
}
类摘要扩展了无状态小部件{
@凌驾
小部件构建(构建上下文){
返回文本(“摘要”);
}
}
bool btnenabled = false;
...
Widget build(BuildContext context) {
import 'package:flutter/material.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
bool btnenabled = false;
String _currentaddress = "";
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.red,
title: Text('Address'),
),
body: Column(
children: <Widget>[
TextFormField(onChanged: (newValue) {
_currentaddress = 'addressJSON' + newValue;
if (newValue.length > 0) {
setState(() {
btnenabled = true;
});
}
}),
TextButton(
style: TextButton.styleFrom(
backgroundColor: Colors.blue[700], primary: Colors.white),
child: Text(
'next',
),
onPressed: btnenabled == true
? () => Navigator.push(context,
MaterialPageRoute(builder: (context) => Summary()))
: null)
],
),
);
}
}
class Summary extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Text("Summary");
}
}