[英]Adding elements to the List inside setState() method, not saving element Flutter
[英]Setstate is not working inside list of widgets flutter
我的問題是我的列表中的 Raisedbutton 沒有改變 position ontap 而留在小部件列表中請幫助我並告訴我該代碼有什么問題
class Sticker extends
StatefulWidget {
Sticker({Key key}) :
super(key: key);
@override
_StickerState
createState() => _
StickerState();
}
class _StickerState extends
State<Sticker> {
Offset position =
Offset(50, 100);
List<Widget> list = [];
@override
Widget build(BuildContext
context) {
return Container(
child: Stack(
children: [
Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
),
Positioned(
left: 50,
top: 50,
child:
RaisedButton(
onPressed: () {
setState(
() {
list.add(
Positioned(
left: position.dx,
top: position.dy,
child: RaisedButton(
onPressed: () {
setState(() => position = Offset(50, 150));
},
),
),
);
},
);
},
),
),
...list
],
),
);
}
}
我希望在留在列表中時點擊它后我提出的更改 position 請幫我解決這個問題 控制台沒有給出錯誤
您可以在下面復制粘貼運行完整代碼
您可以使用StatefulBuilder
list.add(StatefulBuilder(
builder: (BuildContext context, StateSetter setState) {
return Positioned(
工作演示
完整代碼
import 'package:flutter/material.dart';
class Sticker extends StatefulWidget {
Sticker({Key key}) : super(key: key);
@override
_StickerState createState() => _StickerState();
}
class _StickerState extends State<Sticker> {
Offset position = Offset(50, 100);
List<Widget> list = [];
@override
Widget build(BuildContext context) {
print("build list.length ${list.length}");
return Container(
child: Stack(
children: [
Container(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
),
Positioned(
left: 50,
top: 50,
child: RaisedButton(
onPressed: () {
setState(
() {
list.add(StatefulBuilder(
builder: (BuildContext context, StateSetter setState) {
return Positioned(
left: position.dx,
top: position.dy,
child: RaisedButton(
onPressed: () {
setState(() {
position = Offset(50, 150);
});
},
),
);
}));
},
);
},
),
),
...list
],
),
);
}
}
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
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> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Sticker(),
);
}
}
我認為您必須為列表中的每個按鈕創建一個 position 元素
List<Offset> position = Offset();
setState(() => position.add(Offset(50,150)));
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