[shared_preferences] Document the need to use reload when using multiple isolates or engines #101691
Description
I am working on this Flutter app and I have implemented Firebase Cloud Messaging. I added the following code to make sure I can use the Shared Preferences package. It seems to work, but the functionality does not work correctly.
if (Platform.isAndroid) SharedPreferencesAndroid.registerWith();
if (Platform.isIOS) SharedPreferencesIOS.registerWith();The backgroundhandler in action:
Future<void> backgroundHandler(RemoteMessage message) async {
await Firebase.initializeApp();
if (Platform.isAndroid) SharedPreferencesAndroid.registerWith();
if (Platform.isIOS) SharedPreferencesIOS.registerWith();
print("App is in background: Message received ");
String productId = message.data['productId'];
SendPort mainToIsolateStream = (await initIsolate()) as SendPort;
final prefs = await SharedPreferences.getInstance();
final listOfTopics = prefs.getStringList('out_of_stock_topics') ?? [];
print('BEFORE unsubscribe, print list of topics: $listOfTopics');
// Returns locale string in 'en_US'
// String defaultLocale = Platform.localeName;
String defaultLocale = prefs.getString('language') ?? "";
String topic = '${productId}_$defaultLocale';
print('The topic: ${topic}');
print("The list of topics: ${listOfTopics}");
// Check if topic already exists
if (listOfTopics.contains(topic)) {
print("Topic deleted");
LocalNotificationService.unsubscribeToTopic(topic);
listOfTopics.remove(topic);
print(listOfTopics.length);
await prefs.setStringList('out_of_stock_topics', listOfTopics);
}
}The code above deletes the topic in the list. Then the list is set with prefs.setStringList. I checked, and the code goes into the if statement. It removes the item from the list. But something goes wrong in prefs.setStringList I suppose.
Because later I use the following code to check the items in the 'out_of_stock_topics' list.
final prefs = await SharedPreferences.getInstance();
final listOfTopics =
prefs.getStringList('out_of_stock_topics') ?? [];
print(listOfTopics);But the topic is not correctly deleted and is still there. I think there is something wrong in the backend of the backgroundhandler. I tested this feature with 2 buttons: "add topic" and "delete topic". And with those separate buttons it does delete the item from the 'out_of_stock_topics' list.
Does anyone know how to fix this problem?
Thanks!