我想在Flutter的有狀態小部件中顯示簡單SnackBar。我的應用程序使用名爲MyHomePage的有狀態小部件創建MaterialApp的新實例。在Flutter中顯示SnackBar
我嘗試在showSnackBar()方法中顯示SnackBar。但它失敗,'方法'showSnackBar'被調用爲空'。
這段代碼有什麼問題?
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key}) : super(key: key);
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();
@override
void initState() {
super.initState();
showInSnackBar("Some text");
}
@override
Widget build(BuildContext context) {
return new Padding(
key: _scaffoldKey,
padding: const EdgeInsets.all(16.0),
child: new Text("Simple Text")
);
}
void showInSnackBar(String value) {
_scaffoldKey.currentState.showSnackBar(new SnackBar(
content: new Text(value)
));
}
}
SOLUTION:
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new Scaffold(body: new MyHomePage()),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key}) : super(key: key);
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
void initState() {
super.initState();
}
@override
Widget build(BuildContext context) {
showInSnackBar("Some text");
return new Padding(
padding: const EdgeInsets.all(16.0),
child: new Scaffold(
body: new Text("Simple Text")
)
);
}
void showInSnackBar(String value) {
Scaffold.of(context).showSnackBar(new SnackBar(
content: new Text(value)
));
}
}
用新的'Scaffold'封裝我的StatefulWidget並使用'Scaffold.of(context)'代替'_scaffoldKey'引用幫助。謝謝! –