在Android中，每个单独的View子类都有一个setVisibility()方法，允许你修改View对象的可见性
有3个设置可见性的选项:
可见:在布局中显示视图 不可见:隐藏视图，但留下一个空白，相当于视图在可见时所占据的空白 消失:隐藏视图，并将其完全从布局中移除。就好像它的高和宽都是0dp
对于Flutter中的小部件，是否有与上述相同的东西?
快速参考: https://developer.android.com/reference/android/view/View.html#attr_android:visibility
当前回答
在flutter 1.5和Dart 2.3中，对于可视性消失，您可以在集合中使用if语句设置可见性，而不必使用容器。
e.g
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text('This is text one'),
if (_isVisible) Text('can be hidden or shown'), // no dummy container/ternary needed
Text('This is another text'),
RaisedButton(child: Text('show/hide'), onPressed: (){
setState(() {
_isVisible = !_isVisible;
});
},)
],
)
其他回答
恕我直言，在Flutter中不需要可见性属性或特殊的小部件，因为如果你不需要显示小部件，就不要将其添加到小部件树中或将其替换为空小部件:
@override
Widget build(BuildContext context) {
return someFlag ? Text('Here I am') : SizedBox();
}
我认为能见度小部件存在的原因是因为很多人问:)人们习惯了由某些属性控制的元素的可见性
更新:因为这个答案是写的，可见性被引入，并提供了这个问题的最佳解决方案。
你可以在不透明度:为0.0的情况下使用不透明度来绘制隐藏的元素，但仍然占用空间。
为了使它不占用空间，将其替换为空Container()。
编辑: 要将它包装在不透明对象中，请执行以下操作:
new Opacity(opacity: 0.0, child: new Padding(
padding: const EdgeInsets.only(
left: 16.0,
),
child: new Icon(pencil, color: CupertinoColors.activeBlue),
))
谷歌开发者不透明度快速教程:https://youtu.be/9hltevOHQBw
也许你可以像这样使用Navigator函数Navigator.of(context).pop();
与问题协作，并展示一个用空Container()替换它的示例。
下面是一个例子:
import "package:flutter/material.dart";
void main() {
runApp(new ControlleApp());
}
class ControlleApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: "My App",
home: new HomePage(),
);
}
}
class HomePage extends StatefulWidget {
@override
HomePageState createState() => new HomePageState();
}
class HomePageState extends State<HomePage> {
bool visibilityTag = false;
bool visibilityObs = false;
void _changed(bool visibility, String field) {
setState(() {
if (field == "tag"){
visibilityTag = visibility;
}
if (field == "obs"){
visibilityObs = visibility;
}
});
}
@override
Widget build(BuildContext context){
return new Scaffold(
appBar: new AppBar(backgroundColor: new Color(0xFF26C6DA)),
body: new ListView(
children: <Widget>[
new Container(
margin: new EdgeInsets.all(20.0),
child: new FlutterLogo(size: 100.0, colors: Colors.blue),
),
new Container(
margin: new EdgeInsets.only(left: 16.0, right: 16.0),
child: new Column(
children: <Widget>[
visibilityObs ? new Row(
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
new Expanded(
flex: 11,
child: new TextField(
maxLines: 1,
style: Theme.of(context).textTheme.title,
decoration: new InputDecoration(
labelText: "Observation",
isDense: true
),
),
),
new Expanded(
flex: 1,
child: new IconButton(
color: Colors.grey[400],
icon: const Icon(Icons.cancel, size: 22.0,),
onPressed: () {
_changed(false, "obs");
},
),
),
],
) : new Container(),
visibilityTag ? new Row(
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
new Expanded(
flex: 11,
child: new TextField(
maxLines: 1,
style: Theme.of(context).textTheme.title,
decoration: new InputDecoration(
labelText: "Tags",
isDense: true
),
),
),
new Expanded(
flex: 1,
child: new IconButton(
color: Colors.grey[400],
icon: const Icon(Icons.cancel, size: 22.0,),
onPressed: () {
_changed(false, "tag");
},
),
),
],
) : new Container(),
],
)
),
new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new InkWell(
onTap: () {
visibilityObs ? null : _changed(true, "obs");
},
child: new Container(
margin: new EdgeInsets.only(top: 16.0),
child: new Column(
children: <Widget>[
new Icon(Icons.comment, color: visibilityObs ? Colors.grey[400] : Colors.grey[600]),
new Container(
margin: const EdgeInsets.only(top: 8.0),
child: new Text(
"Observation",
style: new TextStyle(
fontSize: 12.0,
fontWeight: FontWeight.w400,
color: visibilityObs ? Colors.grey[400] : Colors.grey[600],
),
),
),
],
),
)
),
new SizedBox(width: 24.0),
new InkWell(
onTap: () {
visibilityTag ? null : _changed(true, "tag");
},
child: new Container(
margin: new EdgeInsets.only(top: 16.0),
child: new Column(
children: <Widget>[
new Icon(Icons.local_offer, color: visibilityTag ? Colors.grey[400] : Colors.grey[600]),
new Container(
margin: const EdgeInsets.only(top: 8.0),
child: new Text(
"Tags",
style: new TextStyle(
fontSize: 12.0,
fontWeight: FontWeight.w400,
color: visibilityTag ? Colors.grey[400] : Colors.grey[600],
),
),
),
],
),
)
),
],
)
],
)
);
}
}
初学者也可以试试。
class Visibility extends StatefulWidget {
@override
_VisibilityState createState() => _VisibilityState();
}
class _VisibilityState extends State<Visibility> {
bool a = true;
String mText = "Press to hide";
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: "Visibility",
home: new Scaffold(
body: new Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new RaisedButton(
onPressed: _visibilitymethod, child: new Text(mText),),
a == true ? new Container(
width: 300.0,
height: 300.0,
color: Colors.red,
) : new Container(),
],
)
),
);
}
void _visibilitymethod() {
setState(() {
if (a) {
a = false;
mText = "Press to show";
} else {
a = true;
mText = "Press to hide";
}
});
}
}
