Xamarin Android Notification not Showing in Foreground

Question

I am using Azure Hubs to send notifications. I am able to receive the notification and it displays on the device when I pull down the notifications window. However, I do not see the notification display at the top of the screen as expected. I even "locked" the screen and it didn't display. I got the notification sound and my logs show I received it.

Screen showing received notification

My FirebaseMessageService:

using System;
using System.Linq;
using WindowsAzure.Messaging;
using Android.App;
using Android.Content;
using Android.Support.V4.App;
using Android.Util;
using Firebase.Messaging;
using IDEQ.AQI.Pages;

namespace IDEQ.AQI.Droid
{
    [Service]
    [IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
    public class FirebaseService : FirebaseMessagingService
    {
        const string Tag = "FirebaseMsgService";

        public override void OnNewToken(string token)
        {
            // NOTE: save token instance locally, or log if desired

            SendRegistrationToServer(token);
        }

        private void SendRegistrationToServer(string token)
        {
            try
            {
                var hub = new NotificationHub(Constants.NotificationHubName, Constants.ListenConnectionString, this);

                // register device with Azure Notification Hub using the token from FCM
                var registration = hub.Register(token, Constants.SubscriptionTags);

                // subscribe to the SubscriptionTags list with a simple template.
                var pnsHandle = registration.PNSHandle;
                var templateReg = hub.RegisterTemplate(pnsHandle, "defaultTemplate", Constants.FCMTemplateBody, Constants.SubscriptionTags);
            }
            catch (Exception e)
            {
                Log.Error(Constants.DebugTag, $"Error registering device: {e.Message}");
            }
        }

        public override void OnMessageReceived(RemoteMessage message)
        {
            base.OnMessageReceived(message);
            string messageBody;


            Log.Info(Tag, "From: " + message.From);

            if (message.GetNotification() != null)
            {
                Log.Info(Tag, "Notification Message Body: " + message.GetNotification().Body);
                messageBody = message.GetNotification().Body;
            }

            // NOTE: test messages sent via the Azure portal will be received here
            else
            {
                messageBody = message.Data.Values.First();
            }

            // convert the incoming message to a local notification
            SendLocalNotification(messageBody);

            // send the incoming message directly to the MainPage
            SendMessageToMainPage(messageBody);
        }

        private void SendLocalNotification(string body)
        {
            try
            {
                var intent = new Intent(this, typeof(MainActivity));
                intent.AddFlags(ActivityFlags.ClearTop);
                intent.PutExtra("message", body);

                var requestCode = new Random().Next();
                var pendingIntent = PendingIntent.GetActivity(this, requestCode, intent, PendingIntentFlags.OneShot);

                var notificationBuilder = new NotificationCompat.Builder(this, Constants.NotificationChannelId)
                    .SetContentTitle("IDEQ Alert")
                    .SetSmallIcon(Resource.Drawable.ic_launcher)
                    .SetContentText(body)
                    .SetAutoCancel(true)
                    .SetShowWhen(false)
                    .SetContentIntent(pendingIntent);

                var notificationManager = NotificationManagerCompat.From(this);
                notificationManager.Notify(0, notificationBuilder.Build());
            }
            catch (Exception e)
            {
                Log.Error(Tag, e.ToString());
            }
        }

        private void SendMessageToMainPage(string body)
        {
            (Xamarin.Forms.Application.Current.MainPage as MainPage)?.AddMessage(body);
        }
    }
}

//My main activity where I create the channel:

private void CreateNotificationChannel()
{
    if (Build.VERSION.SdkInt < BuildVersionCodes.O)
    {
        // Notification channels are new in API 26 (and not a part of the
        // support library). There is no need to create a notification
        // channel on older versions of Android.
        return;
    }

    var channel = new NotificationChannel(Constants.NotificationChannelId, Constants.NotificationChannelName, NotificationImportance.Default)
    {
        Description = string.Empty
    };

    var notificationManager = (NotificationManager) GetSystemService(NotificationService);
    notificationManager.CreateNotificationChannel(channel);
}

Answer 1

Notification in your system tray will only be displayed if application is in background or turned off. If your application is running, your OnMessageRecieved method will get hit, however Android will not display notification in the system try. This is how life cycle of push notification works in Android. The only way u can display notification in system tray when application in in foreground is when you force Local Notification like you did in SendLocalNotification method.