Flutter 运行报错:MediaQuery.of() called with a context that does not contain a MediaQuery

LoginPage()是写好的用户登录界面，但是想让界面跑起来 需要runApp()，需要再写个MyApp()里面使用MaterialApp（）包裹写好的界面

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter_LoginPlugin',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: LoginPage(),
    );
  }

}

class LoginPage  extends StatefulWidget{
  @override
  State createState() {
    return new _MyAppState();
  }

}


class _MyAppState extends State {
   //布局页面
}