Milèstre BV
Aug 21, 2020

Xamarin Forms: Update Notification Tags with Azure Notification Hub



Normally when you install a new app that supports push notifications with Azure Notification Hub, a new token is generated after first startup. At that moment tags are registered as well.

But what if you want to update these notifications tag on a later moment, for instance after a login? Then you have to update the tag!

How can you do that?

I am using the NotificationHubSample, Microsoft has created. You can find it here: https://github.com/xamarin/xamarin-forms-samples/tree/master/WebServices/AzureNotificationHub/NotificationHubSample

As soon as the new token is generated, we have to store it secure because we need it during update of the notification tags:

In Android in FirebaseService.cs:

public async override void OnNewToken(string token)

{

    SendRegistrationToServer(token);

    await SecureStorage.SetAsync("newnotificationtoken", "true");

}

In iOS in AppDelegate.cs:

public override async void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)

{

    try

    {

        Hub = new SBNotificationHub(General.ListenConnectionString, General.NotificationHubName);

 

        // update registration with Azure Notification Hub

        Hub.UnregisterAll(deviceToken, (error) =>

        {

            if (error != null)

            {

                Crashes.TrackError(new System.InvalidOperationException($"Unable to call unregister {error}"));

                return;

            }

 

            var tags = new NSSet(General.SubscriptionTags.ToArray());

            Hub.RegisterNative(deviceToken, tags, (errorCallback) =>

            {

                if (errorCallback != null)

                {

                    Crashes.TrackError(new System.InvalidOperationException($"RegisterNativeAsync error: {errorCallback}"));

                }

            });

 

            var templateExpiration = DateTime.Now.AddDays(120).ToString(System.Globalization.CultureInfo.CreateSpecificCulture("en-US"));

            Hub.RegisterTemplate(deviceToken, "defaultTemplate", General.APNTemplateBody, templateExpiration, tags, (errorCallback) =>

            {

                if (errorCallback != null)

                {

                    if (errorCallback != null)

                    {

                        Crashes.TrackError(new System.InvalidOperationException($"RegisterTemplateAsync error: {errorCallback}"));

                    }

                }

            });

 

        });

 
        //convert it to a base64 string that can be stored and used later when you want to update the tag

        string token = deviceToken.getBase64EncodedString(NSDataBase64EncodingOptions.None);

        await SecureStorage.SetAsync("notificationtoken", token);

 

    } catch (Exception ex)

    {

        Crashes.TrackError(ex));

    }

} 

Then we are going to create Dependency objects in Android and iOS.

First create an interface class in you shared project

namespace Xamarin_Support.Interfaces

{

    public interface INotificationHelper

    {

        void UpdateToken(string token, string[] subscriptionTags);

    }

}

In Android project create a new dependency object NotificationHelper, that is based on the above interface class.

using notification_App.Droid.Helpers;

using Plugin.CurrentActivity;

using System.Threading.Tasks;

using WindowsAzure.Messaging;

using Xamarin.Forms;

using Xamarin_Support.Helpers;

using Xamarin_Support.Interfaces;

 

[assembly: Dependency(typeof(NotificationHelper))]

namespace notification_App.Droid.Helpers

{

    public class NotificationHelper : INotificationHelper

    {

        public async void UpdateToken(string token, string[] subscriptionTags)

        {

            NotificationHub hub = new NotificationHub(General.NotificationHubName, General.ListenConnectionString, CrossCurrentActivity.Current.Activity);

 

            //run on different thread, not on ui thread to prevent an exception

            await Task.Run(() => {

                //First unregister from current tags

                hub.Unregister();

                // register new tags with Azure Notification Hub using the token from FCM

                hub.Register(token, subscriptionTags);

            });

        }

    }

} 

In iOS project also, create a new dependency object NotificationHelper, that is based on the above interface class.

using notification_App.iOS.Helpers;

using Foundation;

using Microsoft.AppCenter.Crashes;

using System.Linq;

using WindowsAzure.Messaging;

using Xamarin.Forms;

using Xamarin_Support.Helpers;

using Xamarin_Support.Interfaces;

 

[assembly: Dependency(typeof(NotificationHelper))]

namespace notification_App.iOS.Helpers

{

    public class NotificationHelper : INotificationHelper

    {

        public void UpdateToken(string token, string[] subscriptionTags)

        {

            SBNotificationHub Hub = new SBNotificationHub(General.ListenConnectionString, General.NotificationHubName);

 

            NSData deviceToken = new NSData(token, NSDataBase64DecodingOptions.None);

            Hub.UnregisterAll(deviceToken, (error) =>

            {

                if (error != null)

                {

                    Crashes.TrackError(new System.InvalidOperationException($"Unable to call unregister {error}"));

                    return;

                }

 

                var tags = new NSSet(subscriptionTags.ToArray());

                Hub.RegisterNative(deviceToken, tags, (errorCallback) =>

                {

                    if (errorCallback != null)

                    {

                        Crashes.TrackError(new System.InvalidOperationException($"RegisterNativeAsync error: {errorCallback}"));

                    }

                });

            });

        }

    }

} 

Now you are ready to update the notification tags, whereever you want, for instance after a succesfull login:

INotificationHelper notificationHelper = DependencyService.Get<INotificationHelper>();

//get the sored token

string notificationToken = await SecureStorage.GetAsync("notificationtoken");

//create new tag array

string[] subscriptionTags = new string[] { customerId };


//update tags

notificationHelper.UpdateToken(notificationToken, subscriptionTags); 



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