在初始化共享偏好变量时，我在颤振中出现错误

Question

下面是我的代码，现在工作很好，我已经初始化了共享偏好变量，并用它来检查它是否为空，如果不是空，它将导航到主页，如果为空，那么它将留在登录页面。我已经在Material App中初始化了共享偏好，但现在的问题是，我想使用有状态的My App类在我的应用中使用One Signal实现推送通知。我在这里附加了一个信号代码，我想在我的应用程序中实现，但因为我已经在runapp中使用了材料应用程序，我面临着问题。请给我一个解决办法。

当前主要。使用共享首选项正常工作的Dart文件:

Future main() async {
WidgetsFlutterBinding.ensureInitialized();
SharedPreferences prefs = await SharedPreferences.getInstance();
var usrEmail = prefs.getString('email');
//print(email);
// await SystemChrome.setPreferredOrientations([
//   DeviceOrientation.portraitUp,
//   DeviceOrientation.portraitDown,
// ]);
runApp(
//MultiProvider(
//  providers: [ChangeNotifierProvider(create: (_) => ChangeStatus())],
MaterialApp(
debugShowCheckedModeBanner: false,
title: "ATDOCHUB Dev",
// theme: ThemeData(
//   colorScheme: ColorScheme.fromSwatch(primarySwatch: Colors.blue)
//       .copyWith(secondary: Colors.white70),
// ),
home: usrEmail == null ? LoginPage() : homePageAdmin(),
));
}

主要。我想为推送通知实现的dart文件:

import 'package:flutter/material.dart';
import 'package:newsapp/screens/home_screen.dart';
import 'package:newsapp/screens/notification.dart';
import 'package:onesignal_flutter/onesignal_flutter.dart';
import './utilities/globals.dart' as globals;
void main() {
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({Key? key}) : super(key: key);
@override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
// This widget is the root of your application.
@override
void initState() {
// TODO: implement initState
super.initState();
initPlatformState();
}
Future<void> initPlatformState() async {
OneSignal.shared.setLogLevel(OSLogLevel.verbose, OSLogLevel.none);
OneSignal.shared
.setNotificationOpenedHandler((OSNotificationOpenedResult result) {
debugPrint('NOTIFICATION OPENED HANDLER CALLED WITH: $result');
setState(() {});
globals.appnavigator.currentState
?.push(MaterialPageRoute(builder: (context) => const NotificationHome()));
});
OneSignal.shared.setNotificationWillShowInForegroundHandler(
(OSNotificationReceivedEvent event) {

setState(() {});
});
await OneSignal.shared.setAppId("d27b4c45-540c-41fb-b0c2-0f92cd13a664");
}
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.indigo,
),
home: const HomeScreen(),
);
}
}

Answer 1

首先为共享首选项创建一个单独的服务。

class SharedPrefService {
static late SharedPreferences pref;
static Future<void> init() async {
pref = await SharedPreferences.getInstance();
}
}

现在在main函数中调用这个init方法，如下所示。

main() async {
WidgetsFlutterBinding.ensureInitialized();
await SharedPrefService.init();
}

现在你可以在整个应用程序中使用这个实例，只要调用

SharedPrefService.pref.///

不需要在任何地方初始化共享首选项，只需使用单个实例。如果你想在隔离或后台服务中使用sharedpreferences，那么你将需要再次初始化共享首选项，因为不同的线程。