Flutter -构建过程中调用的setState()
Flutter -构建过程中调用的setState()
提问于 2019-02-14 05:24:18
我对Flutter真的很陌生，所以我不知道发生了什么。我试着做一个简单的视图，选择一张卡，按下一个按钮，然后移动到一个新的屏幕。因此，每当我选择一张卡时，我都需要更新类变量以反映这种变化，但是仿真器屏幕给出了一个错误，提示我在构建期间调用了setState()。其他类似的帖子没有给我一个适用于这种情况的解决方案。
import 'package:flutter/material.dart';
import 'package:fluttertest/pick_one_image.dart';
import 'package:fluttertest/pick_two_images.dart';
class AlgorithmSelect extends StatefulWidget {
@override
State createState() => new AlgorithmSelectState();
}
class AlgorithmSelectState extends State<AlgorithmSelect> {
bool isDefault = false;
bool isRubik = false;
bool isMeaningful = false;
int numImages = 0;
bool showProgressCircle = false;
defaultSelected() {
setState(() {
isDefault = !isDefault;
isRubik = false;
isMeaningful = false;
});
}
rubikSelected() {
setState(() {
isDefault = false;
isRubik = !isRubik;
isMeaningful = false;
});
}
meaningfulSelected() {
setState(() {
isDefault = false;
isRubik = false;
isMeaningful = !isMeaningful;
});
}
@override
Widget build(BuildContext context) {
var titleBorder = new BorderDirectional(top: new BorderSide(color: Colors.blue, width: 3.0), start: new BorderSide(color: Colors.blue, width: 3.0), end: new BorderSide(color: Colors.blue, width: 3.0));
var detailBorder = new BorderDirectional(bottom: new BorderSide(color: Colors.blue, width: 3.0), start: new BorderSide(color: Colors.blue, width: 3.0), end: new BorderSide(color: Colors.blue, width: 3.0));
var title = new Container(
padding: EdgeInsets.all(20.0),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Text("Select an encryption algorithm:", textScaleFactor: 1.7,)
],
),
);
var defaultTitle = new Card(
shape: isDefault ? titleBorder : null,
margin: EdgeInsets.fromLTRB(20.0, 20.0, 20.0, 0.0),
child: new Container(
decoration: new BoxDecoration(color: Colors.lightBlueAccent),
child: new Column(
children: <Widget>[
new Padding(padding: EdgeInsets.fromLTRB(2.5, 0.5, 2.5, 2.5),),
new Text("Default", textScaleFactor: 1.5, style: new TextStyle(color: Colors.white,)),
],
),
),
);
var defaultDetails = new Card(
shape: isDefault ? detailBorder : null,
margin: EdgeInsets.fromLTRB(20.0, 0.0, 20.0, 20.0),
child: new Container(
decoration: new BoxDecoration(color: Colors.white),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Padding(padding: EdgeInsets.all(10.0),),
new Text(" • Randomized internals", textScaleFactor: 1.0, style: new TextStyle(color: Colors.black),),
new Padding(padding: EdgeInsets.all(10.0),)
],
),
),
);
var rubikTitle = new Card(
shape: isRubik ? titleBorder : null,
margin: EdgeInsets.fromLTRB(20.0, 0.0, 20.0, 0.0),
child: new Container(
decoration: new BoxDecoration(color: Colors.teal),
child: new Column(
children: <Widget>[
new Padding(padding: EdgeInsets.fromLTRB(2.5, 0.5, 2.5, 2.5),),
new Text("Rubik", textScaleFactor: 1.5, style: new TextStyle(color: Colors.white,)),
],
),
),
);
var rubikDetails = new Card(
shape: isRubik ? detailBorder : null,
margin: EdgeInsets.fromLTRB(20.0, 0.0, 20.0, 0.0),
child: new Container(
decoration: new BoxDecoration(color: Colors.white),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Padding(padding: EdgeInsets.all(10.0),),
new Text(" • Uses the Rubik's cube principle of circular shifts", textScaleFactor: 1.0, style: new TextStyle(color: Colors.black),),
],
),
),
);
var meaningfulTitle = new Card(
shape: isMeaningful ? titleBorder : null,
margin: EdgeInsets.fromLTRB(20.0, 20.0, 20.0, 0.0),
child: new Container(
decoration: new BoxDecoration(color: Colors.indigo),
child: new Column(
children: <Widget>[
new Padding(padding: EdgeInsets.fromLTRB(2.5, 0.5, 2.5, 2.5),),
new Text("Arnold Transformation", textScaleFactor: 1.5, style: new TextStyle(color: Colors.white,)),
],
),
),
);
var meaningfulDetails = new Card(
shape: isMeaningful ? detailBorder : null,
margin: EdgeInsets.fromLTRB(20.0, 0.0, 20.0, 20.0),
child: new Container(
decoration: new BoxDecoration(color: Colors.white),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Padding(padding: EdgeInsets.all(10.0),),
new Text(" • Uses Arnold Transformation", textScaleFactor: 1.0, style: new TextStyle(color: Colors.black),),
],
),
),
);
return new Scaffold(
appBar: new AppBar(
// title: 'Select an algorithm',
// centerTitle: true,
backgroundColor: Colors.blue,
),
body:
showProgressCircle ?
new Center(
child: new Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
CircularProgressIndicator()
])
)
:
new ListView(
children: [
title,
new GestureDetector(
child: defaultTitle,
onTap: this.defaultSelected,
),
new GestureDetector(
child: defaultDetails,
onTap: this.defaultSelected,
),
new GestureDetector(
child: rubikTitle,
onTap: this.rubikSelected,
),
new GestureDetector(
child: rubikDetails,
onTap: this.rubikSelected,
),
new GestureDetector(
child: meaningfulTitle,
onTap: this.meaningfulSelected,
),
new GestureDetector(
child: meaningfulDetails,
onTap: this.meaningfulSelected,
),
new Container (
margin: EdgeInsets.fromLTRB(120, 20, 120, 20),
child: new RaisedButton(
child: new Text("Encrypt!", textScaleFactor: 1.5),
padding: EdgeInsets.fromLTRB(20, 15, 20, 15),
color: Colors.blue,
onPressed: (isDefault || isRubik || isMeaningful) ? navigate() : null,
)
)
]
),
);
}
}回答 2
Stack Overflow用户
回答已采纳
发布于 2019-02-14 06:31:44
更改此行：
onPressed: (isDefault || isRubik || isMeaningful) ? navigate() : null,要这样做：
onPressed: (isDefault || isRubik || isMeaningful) ? navigate : null,Stack Overflow用户
发布于 2019-02-14 13:18:30
我认为它更有意义，如果你稍微扩展一下，它会读得更好。
从这个开始：
onPressed: (isDefault || isRubik || isMeaningful) ? navigate() : null,要这样做：
onPressed: () {
if (isDefault || isRubik || isMeaningful) navigate();
},
enabled: (isDefault || isRubik || isMeaningful),通过onPressed回调传递空值会导致按钮被标记为禁用。这样，它仍将使用相同的逻辑被禁用。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/54679658
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