Register for notifications (FCM) outside AppDelegate - ios

Question

I want to ask the user to allow notifications only when we prompt the "AskNotification" view and when he click on "Yes".
In order to do that, I did the following :
public static AppDelegate Self { get; private set; }
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
HtmlLabelRenderer.Initialize();
global::Xamarin.Forms.Forms.Init();
// Notifications
Firebase.Core.App.Configure();
//AllowNotifications();
...
LoadApplication(new App());
AppDelegate.Self = this;
return base.FinishedLaunching(app, options);
}
public void AllowNotifications()
{
//In iOS you must request permission to show local / remote notifications first since it is a user interrupting action.
if (UIDevice.CurrentDevice.CheckSystemVersion(10, 0))
{
// Request Permissions
UNUserNotificationCenter.Current.RequestAuthorization(
UNAuthorizationOptions.Alert | UNAuthorizationOptions.Badge | UNAuthorizationOptions.Sound,
(granted, error) =>
{
// Do something if needed
});
// For iOS 10 display notification (sent via APNS)
UNUserNotificationCenter.Current.Delegate = this;
// For iOS 10 data message (sent via FCM)
Messaging.SharedInstance.Delegate = this;
}
else
{
// iOS 9 or before
var allNotificationTypes = UIUserNotificationType.Alert
| UIUserNotificationType.Badge
| UIUserNotificationType.Sound;
var settings = UIUserNotificationSettings
.GetSettingsForTypes(allNotificationTypes, null);
UIApplication.SharedApplication.RegisterUserNotificationSettings(settings);
}
Messaging.SharedInstance.ShouldEstablishDirectChannel = true;
Console.WriteLine("-------- RegisterForRemoteNotifications");
UIApplication.SharedApplication.RegisterForRemoteNotifications();
}
And then on my Code Behind when the user click on the "Allow" button (from my view) I do the following :
AppDelegate appDelegate = AppDelegate.Self;
appDelegate.AllowNotifications();
As you can see, I'm using the Singleton pattern to have an access to the AppDelegate. My problem is when the "AllowNotifications" is called inside the AppDelegate (it's commented on the code above), the system prompt ask for the user and notifications are received.
But when I call the AllowNotification method from another page with the Singleton pattern. The system popup is showing, we the user click "Yes" it allow notification on iOS parameters. But I never get into my "DidReceiveMessage" method.
Thanks for your help

Answer 1

This issue has nothing to do with your code.It is an expected behavior.Because you used firebase (Xamarin.Firebase.iOS.CloudMessaging from NuGet).
For devices running iOS 10 and above, you must assign your delegate object to the UNUserNotificationCenter object to receive display notifications, and the FIRMessaging object to receive data messages, before your app finishes launching. For example, in an iOS app, you must assign it in the method FinishedLaunching.
That is to say,when you register for notifications out the method FinishedLaunching,even if system popup showed,the register will still not working.
For more detail you can refer here.