Flutter StatefulWidget中的setState()工作不正常
我想做的是,在单击按钮时更改Flutter StatefulWidget中的setState()工作不正常,flutter,dart,statefulwidget,Flutter,Dart,Statefulwidget,我想做的是,在单击按钮时更改RawMaterialButton的颜色。阅读有关StatefulWidget的文章,它看起来应该可以工作,但由于某些原因它不能工作 flatter:引发了另一个异常:在构造函数:ButtonTest#1a93b中调用了setState()(生命周期状态:已创建,无小部件,未装入) 按钮测试等级: class ButtonState extends StatefulWidget { @override State createState() => But
RawMaterialButton
的颜色。阅读有关StatefulWidget的文章,它看起来应该可以工作,但由于某些原因它不能工作
flatter:引发了另一个异常:在构造函数:ButtonTest#1a93b中调用了setState()(生命周期状态:已创建,无小部件,未装入)
按钮测试等级:
class ButtonState extends StatefulWidget {
@override
State createState() => ButtonTest();
}
class ButtonTest extends State<ButtonState> implements Cipher {
@override
String icon = '';
@override
String title = '';
bool enabled = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(this.title),
),
body: RawMaterialButton(
shape: CircleBorder(side: BorderSide(color: Colors.black)),
fillColor: enabled ? Colors.blue : Colors.red,
onPressed: () {
setState(() {
this.enabled = true;
});
},
padding: EdgeInsets.all(0)),
);
}
}
getCiphers()
getCiphers(){
最终列表密码=新列表();
add(ButtonTest());
返回密码;
}
主要类别:
void main() => runApp(CipherTools());
class CipherTools extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'CipherTools',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: CipherScreen(
ciphers: getCiphers(),
),
);
}
}
class CipherScreen extends StatelessWidget {
final List<Cipher> ciphers;
CipherScreen({Key key, @required this.ciphers}) : super(key: key);
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Ciphers'),
),
body: ListView.builder(
itemCount: ciphers.length,
itemBuilder: (context, index) {
return ListTile(
title: Text(ciphers[index].title),
// When a user taps on the ListTile, navigate to the DetailScreen.
// Notice that we're not only creating a DetailScreen, we're
// also passing the current todo through to it!
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => DetailScreen(cipher: ciphers[index]),
),
);
},
);
},
),
);
}
}
class DetailScreen extends StatelessWidget {
// Declare a field that holds the Todo
final Cipher cipher;
// In the constructor, require a Todo
DetailScreen({Key key, @required this.cipher}) : super(key: key);
@override
Widget build(BuildContext context) {
return cipher.build(context);
}
}
void main()=>runApp(CipherTools());
类CipherTools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:“密码工具”,
主题:主题数据(
主样本:颜色。蓝色,
),
主页:密码屏幕(
密码:getCiphers(),
),
);
}
}
类CipherScreen扩展了无状态小部件{
最终列表密码;
密码屏幕({Key Key,@required this.ciphers}):超级(Key:Key);
@凌驾
小部件构建(构建上下文){
返回脚手架(
appBar:appBar(
标题:文本(“密码”),
),
正文:ListView.builder(
itemCount:ciphers.length,
itemBuilder:(上下文,索引){
返回列表块(
标题:文本(密码[索引]),
//当用户点击ListTile时,导航到Detail屏幕。
//请注意,我们不仅创建了DetailScreen,而且
//也将当前的todo传递给它!
onTap:(){
导航器。推(
上下文
材料路线(
生成器:(上下文)=>DetailScreen(密码:密码[索引]),
),
);
},
);
},
),
);
}
}
类DetailScreen扩展了无状态小部件{
//声明保存Todo的字段
最终密码;
//在构造函数中,需要Todo
DetailScreen({Key Key,@required this.cipher}):super(Key:Key);
@凌驾
小部件构建(构建上下文){
返回cipher.build(上下文);
}
}
我做错了什么?有几件事:
应称为ButtonState
,因为这是ButtonTest
StatefulWidget
应称为ButtonTest
,因为这是ButtonTestState
状态
DetailScreen
中的build()
方法中,可以返回StatefulWidget
(ButtonTest
),如下所示:
@override
Widget build(BuildContext context) {
return ButtonTest();
}
像这样包装setState()
if(this.mounted) {
setState(() {
this.enabled = true;
});
}
请点击链接->
@override
Widget build(BuildContext context) {
return ButtonTest();
}
if(this.mounted) {
setState(() {
this.enabled = true;
});
}