Xamarin.Forms -未调用iOS RegisteredForRemoteNotifications

public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
    // 其他初始化代码...

    // 注册远程通知服务
    if (UIDevice.CurrentDevice.CheckSystemVersion(10, 0))
    {
        UNUserNotificationCenter.Current.RequestAuthorization(UNAuthorizationOptions.Alert | UNAuthorizationOptions.Sound | UNAuthorizationOptions.Badge, (granted, error) =>
        {
            if (granted)
            {
                InvokeOnMainThread(UIApplication.SharedApplication.RegisterForRemoteNotifications);
            }
        });
    }
    else if (UIDevice.CurrentDevice.CheckSystemVersion(8, 0))
    {
        var settings = UIUserNotificationSettings.GetSettingsForTypes(UIUserNotificationType.Alert | UIUserNotificationType.Sound | UIUserNotificationType.Badge, null);
        UIApplication.SharedApplication.RegisterUserNotificationSettings(settings);
        UIApplication.SharedApplication.RegisterForRemoteNotifications();
    }
    else
    {
        var types = UIRemoteNotificationType.Alert | UIRemoteNotificationType.Sound | UIRemoteNotificationType.Badge;
        UIApplication.SharedApplication.RegisterForRemoteNotificationTypes(types);
    }

    return base.FinishedLaunching(app, options);
}