如何在Flutter中以程序方式显示/隐藏Nav Drawer中的菜单项以及启用/禁用应用程序栏中的溢出菜单项

Question

我一直在努力按照标题所说的去做，但在网上根本找不到任何信息。在常规的Android代码中，这很简单，只需找到抽屉/工具栏的ViewID，获取菜单项，然后在菜单项上调用.setEnabled((或.setVisible((。我如何在Flutter中做到这一点？基本上，当某个url加载到webView中时，我想通过程序启用/禁用或显示/隐藏(在webView_flutter的onLoadStart和onLoadFinished方法中(。作为参考，我的脚手架：

return new Scaffold(
appBar: new AppBar(
title: new Text(appBarTitle),
actions: <Widget>[
IconButton(
icon: Icon(
Icons.refresh,
color: Colors.white,
),
onPressed: () {
webView.reload();
},
),
PopupMenuButton<Choice>  ( //showchoice??
onSelected: _select,
itemBuilder: (BuildContext context) {
return choices.map((Choice choice) {
return PopupMenuItem<Choice>(
value: choice,
child: Text(choice.title),
);
}).toList();
},
),
],
),
drawer: Drawer(
child: ListView(
children: <Widget>[
new DrawerHeader(
child: Column (
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.end,
children: <Widget> [
Text(
'HLS Grades',
textAlign: TextAlign.left,
style: TextStyle(
color: Colors.white,
fontSize: 20,
),
),
Text(
'Canvas Online Grading System',
style: TextStyle(
color: Colors.white,
fontSize: 12,
),
),
]),
decoration: BoxDecoration(
color: Colors.blue,
),
),
Divider(),
Text(
'Course Actions',
style: TextStyle(
color: Colors.black,
fontSize: 12,
),
),
ListTile(
leading: Icon(MyFlutterApp.assignment),
title: Text('Assignments'),
onTap: () {
setState(() => _selectedDrawerIndex = 0);
_onSelectNavItem(0);
},
),
ListTile(
leading: Icon(MyFlutterApp.grades),
title: Text('Grades'),
onTap: () {
setState(() => _selectedDrawerIndex = 1);
_onSelectNavItem(1);
},
),
ListTile(
leading: Icon(MyFlutterApp.people),
title: Text('Users'),
onTap: () {
setState(() => _selectedDrawerIndex = 2);
_onSelectNavItem(2);
},
),
ListTile(
leading: Icon(MyFlutterApp.syllabus),
title: Text('Syllabus'),
onTap: () {
setState(() => _selectedDrawerIndex = 3);
_onSelectNavItem(3);
},
),
ListTile(
leading: Icon(MyFlutterApp.discussions),
title: Text('Discussions'),
onTap: () {
setState(() => _selectedDrawerIndex = 4);
_onSelectNavItem(4);
},
),
Divider(),
Text(
'App Actions',
style: TextStyle(
color: Colors.black,
fontSize: 12,
),
),
ListTile(
leading: Icon(MyFlutterApp.logout),
title: Text('Logout'),
onTap: () {
_onSelectNavItem(5);
},
),
ListTile(
leading: Icon(MyFlutterApp.settings),
title: Text('Settings'),
onTap: () {
_onSelectNavItem(6);
},
),
],
),
),

我选择的课程代码：

class Choice {
const Choice({this.title, this.icon});
final String title;
final IconData icon;
}
const List<Choice> choices = const <Choice>[
const Choice(title: 'All Grading Periods'),
const Choice(title: 'Trimester 1'),
const Choice(title: 'Trimester 2'),
const Choice(title: 'Trimester 3'),
];
class ChoiceCard extends StatelessWidget {
const ChoiceCard({Key key, this.choice}) : super(key: key);
final Choice choice;
@override
Widget build(BuildContext context) {
final TextStyle textStyle = Theme.of(context).textTheme.headline4;
return Card(
color: Colors.white,
child: Center(
child: Column(
mainAxisSize: MainAxisSize.min,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Icon(choice.icon, size: 128.0, color: textStyle.color),
Text(choice.title, style: textStyle),
],
),
),
);
}
}

任何帮助都将不胜感激！

Answer 1

对于任何对此感到困惑并正在寻找答案的人，只需将ListTile包装在中即可

Visibility (
visible: _visible
child: ListTile(...)
);

只要你想删除，只需

setState(() {
_visible = false;
});

或者每当你想显示

setState(() {
_visible = true;
});