我正在使用flutter_bloc。
我的代码是这样的:
class Settings extends StatelessWidget {
final _formKey = GlobalKey<FormState>();
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text("SomeApp",style: TextStyle(color: Colors.white)),
automaticallyImplyLeading: false,
backgroundColor: myBlue.shade50,
actions: <Widget>[
IconButton(
icon: new Icon(FontAwesomeIcons.download,color: Colors.white),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => DownloadView()),
);
},
),
IconButton(
icon: new Icon(FontAwesomeIcons.chevronCircleLeft,color: Colors.white),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => MainWindow()),
);
},
),]
),
body: Container(
padding: EdgeInsets.symmetric(vertical: 16),
alignment: Alignment.center,
child: new BlocBuilder<SettingsBloc, SettingsState>(
builder: (context, state) {
if (state is SettingsNotLoaded) {
return new Center(
child: Text(
'count1',
style: TextStyle(fontSize: 24.0,color: Colors.black),
)
);
} else if (state is SettingsLoaded) {
return new Center(
child: Text(
'count2',
style: TextStyle(fontSize: 24.0,color: Colors.black),
)
);
}
else
{
return new Center(
child: Text(
'count3',
style: TextStyle(fontSize: 24.0,color: Colors.black),
)
);
}
},
),
),
);
}
当我启动应用程序时,我看到的应用栏与我想要的一样,但是我在正文中没有看到任何文本(我应该看到count1、count2或count3中的任何一个),而是出现了错误:“Each child must be laid out exactly once." 错误指向第5行 - return new Scaffold(
。当然,我在flutter_bloc页面、https://flutter.dev/docs/development/ui/layout/tutorial、这里以及谷歌上寻找相关信息。
BlocBuilder
会发生什么? - John Joe