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
正如@CopsOnRoad已经强调的那样， 您可以使用Visibility小部件。但是，如果你想保持它的状态，例如，如果你想建立一个viewpager，让一个按钮根据页面出现和消失，你可以这样做
void checkVisibilityButton() {
setState(() {
isVisibileNextBtn = indexPage + 1 < pages.length;
});
}
Stack(children: <Widget>[
PageView.builder(
itemCount: pages.length,
onPageChanged: (index) {
indexPage = index;
checkVisibilityButton();
},
itemBuilder: (context, index) {
return pages[index];
},
controller: controller,
),
Container(
alignment: Alignment.bottomCenter,
child: Row(
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget>[
Visibility(
visible: isVisibileNextBtn,
child: "your widget"
)
],
),
)
]))
其他回答
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],
),
),
),
],
),
)
),
],
)
],
)
);
}
}
也许你可以像这样使用Navigator函数Navigator.of(context).pop();
Flutter现在包含一个可见性小部件，您可以使用它来显示/隐藏小部件。小部件还可以通过更改替换来在两个小部件之间切换。
这个小部件可以实现任何可见、不可见、消失等状态。
Visibility(
visible: true //Default is true,
child: Text('Ndini uya uya'),
//maintainSize: bool. When true this is equivalent to invisible;
//replacement: Widget. Defaults to Sizedbox.shrink, 0x0
),
你可以在你的代码中用一个叫做(Visibility)的新小部件封装任何小部件，这是你想让它不可见的小部件最左边的黄色灯
例如:假设你想让一行不可见:
Click in the lamp and choose (Wrap with widget) Rename the widget to Visibility Add the visible property and set it to false The Child of the newly created widget (Visibility Widget) is the Widget that you want it to be invisible Visibility( visible: false, child: Row( crossAxisAlignment: CrossAxisAlignment.start, children: <Widget>[ SizedBox( width: 10, ), Text("Search", style: TextStyle(fontSize: 20 ),), ], ), ),
我希望它能在将来帮助到别人
bool _visible = false;
void _toggle() {
setState(() {
_visible = !_visible;
});
}
onPressed: _toggle,
Visibility(
visible:_visible,
child: new Container(
child: new Container(
padding: EdgeInsets.fromLTRB(15.0, 0.0, 15.0, 10.0),
child: new Material(
elevation: 10.0,
borderRadius: BorderRadius.circular(25.0),
child: new ListTile(
leading: new Icon(Icons.search),
title: new TextField(
controller: controller,
decoration: new InputDecoration(
hintText: 'Search for brands and products', border: InputBorder.none,),
onChanged: onSearchTextChanged,
),
trailing: new IconButton(icon: new Icon(Icons.cancel), onPressed: () {
controller.clear();
onSearchTextChanged('');
},),
),
),
),
),
),
