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
class VisibilityExample extends StatefulWidget {
const VisibilityExample({Key? key}) : super(key: key);
@override
_VisibilityExampleState createState() => _VisibilityExampleState();
}
class _VisibilityExampleState extends State<VisibilityExample> {
bool visible = false;
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Lines'),
),
body: Container(
color: Colors.black87,
child: Stack(alignment: Alignment.bottomCenter, children: [
ListView(
shrinkWrap: true,
children: [
Container(
height: 200,
),
InkWell(
onTap: () {},
onHover: (value) {
print(value);
setState(() {
visible = !visible;
});
},
child: Visibility(
maintainSize: true,
maintainAnimation: true,
maintainState: true,
visible: visible,
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
IconButton(
color: Colors.white54,
icon: const Icon(
Icons.arrow_left_outlined,
),
onPressed: () {},
),
const SizedBox(
width: 5,
),
IconButton(
color: Colors.white54,
icon: const Icon(
Icons.add_circle_outlined,
),
onPressed: () {},
),
const SizedBox(
width: 5,
),
IconButton(
color: Colors.white54,
icon: const Icon(
Icons.remove_circle,
),
onPressed: () {},
),
const SizedBox(
width: 5,
),
IconButton(
color: Colors.white54,
icon: const Icon(
Icons.arrow_right_outlined,
),
onPressed: () {},
),
const SizedBox(
width: 5,
),
IconButton(
color: Colors.white54,
icon: const Icon(Icons.replay_circle_filled_outlined),
onPressed: () {},
),
],
),
),
),
],
),
]),
),
);
}
}
更新
Flutter现在有一个可见性小部件。要实现您自己的解决方案，请从下面的代码开始。
自己做一个小部件。
显示/隐藏
class ShowWhen extends StatelessWidget {
final Widget child;
final bool condition;
ShowWhen({this.child, this.condition});
@override
Widget build(BuildContext context) {
return Opacity(opacity: this.condition ? 1.0 : 0.0, child: this.child);
}
}
显示/删除
class RenderWhen extends StatelessWidget {
final Widget child;
final bool condition;
RenderWhen({this.child, this.show});
@override
Widget build(BuildContext context) {
return this.condition ? this.child : Container();
}
}
顺便问一下，有没有人对上面的小部件有更好的名字?
更多的阅读
关于如何制作可见性小部件的文章。
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('');
},),
),
),
),
),
),
也许你可以像这样使用Navigator函数Navigator.of(context).pop();
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
