protected override void OnStart()
{
   // This should come before AppCenter.Start() is called
   // Avoid duplicate event registration:
   if (!AppCenter.Configured)
   {
       Push.PushNotificationReceived += (sender, e) =>
       {
           var title = e.Title;
           var message = e.Message;

           // If app is in background title and message are null
           // App in foreground
           if (!string.IsNullOrEmpty(title))
           {
               foreach (string key in e.CustomData.Keys)
               {
                   if (e.CustomData[key] == Settings.WorkerID)
                   {
                      Current.MainPage.DisplayAlert(title, message, "OK");
                   }
               }
           }
        };
   }

   // Handle when your app starts
   AppCenter.Start("android=xxxxxxxxxxxxxxxxxx", typeof(Push));
}