在浮动操作按钮上的onPressed回调中显示支架中的小吃店
问题内容：
我正在尝试打电话
Scaffold.of(context).showSnackBar(SnackBar(
content: Text("Snack text"),
));
里面onPressed的floatingActionButton支架。
我得到这个错误
I/flutter (18613): Scaffold.of() called with a context that does not contain a Scaffold.
I/flutter (18613): No Scaffold ancestor could be found starting from the context that was passed to
....
当您Scaffold.of(context)在体内调用时，它指向一种解决方案。
https://docs.flutter.io/flutter/material/Scaffold/of.html
但是，如果您在onPressed of中调用它，则相同的解决方案将不起作用 FloatingActionButton
问题答案：
更新：第二个解决方案比此解决方案更好。
您应该将floatingActionButton小部件放在构建器小部件中。下面的代码应该工作：
@override
Widget build(BuildContext context) {
return new Scaffold(
floatingActionButton: new Builder(builder: (BuildContext context) {
return new FloatingActionButton(onPressed: () {
Scaffold
.of(context)
.showSnackBar(new SnackBar(content: new Text('Hello!')));
});
}),
body: new Container(
padding: new EdgeInsets.all(32.0),
child: new Column(
children: <Widget>[
new MySwitch(
value: _switchValue,
onChanged: (bool value) {
if (value != _switchValue) {
setState(() {
_switchValue = value;
});
}
},
)
],
),
),
);
