Tutorial: Push notifications to Xamarin.Android apps using Azure Notification Hubs

Overview

This tutorial shows you how to use Azure Notification Hubs to send push notifications to a Xamarin.Android application. You create a blank Xamarin.Android app that receives push notifications by using Firebase Cloud Messaging (FCM). You use your notification hub to broadcast push notifications to all the devices running your app. The finished code is available in the NotificationHubs app sample.

In this tutorial, you take the following steps:

  • Create a Firebase project and enable Firebase Cloud Messaging
  • Create a notification hub
  • Create a Xamarin.Android app and connect it to the notification hub
  • Send test notifications from the Azure portal

Prerequisites

Create a Firebase project and enable Firebase Cloud Messaging

  1. Sign in to the Firebase console. Create a new Firebase project if you don't already have one.

  2. After you create your project, select Add Firebase to your Android app.

    Add Firebase to your Android app

  3. On the Add Firebase to your Android app page, take the following steps:

    1. For the Android package name, enter a name for your package. For example: tutorials.tutoria1.xamarinfcmapp.

      Specify the package name

  4. Select Register app.

  5. Select Download google-services.json. Then save the file into the app folder of your project and select Next.

    Download google-services.json

  6. Select Next.

  7. Select Skip this step.

    Skip the last step

  8. In the Firebase console, select the cog for your project. Then select Project Settings.

    Select Project Settings

  9. If you haven't downloaded the google-services.json file, you can do download it on this page.

  10. Switch to the Cloud Messaging tab at the top.

  11. Copy and save the Legacy Server key for later use. You use this value to configure your notification hub.

Create a notification hub

  1. Sign in to the Azure portal.

  2. Select All services on the left menu, and then select Notification Hubs in the Mobile section. Select the star icon next to the service name to add the service to the FAVORITES section on the left menu. After you add Notification Hubs to FAVORITES, select it on the left menu.

    Azure portal - select Notification Hubs

  3. On the Notification Hubs page, select Add on the toolbar.

    Notification Hubs - Add toolbar button

  4. On the Notification Hub page, do the following steps:

    1. Enter a name in Notification Hub.

    2. Enter a name in Create a new namespace. A namespace contains one or more hubs.

    3. Select a value from the Location drop-down list box. This value specifies the location in which you want to create the hub.

    4. Select an existing resource group in Resource Group, or create a name for a new resource group.

    5. Select Create.

      Azure portal - set notification hub properties

  5. Select Notifications (the bell icon), and then select Go to resource. You can also refresh the list on the Notification Hubs page and select your hub.

    Azure portal - notifications -> Go to resource

  6. Select Access Policies from the list. Note that the two connection strings are available to you. You'll need them later to handle push notifications.

    Important

    Do not use the DefaultFullSharedAccessSignature policy in your application. This is meant to be used in your back end only.

    Azure portal - notification hub connection strings

Configure GCM settings for the notification hub

  1. Select Google (GCM) in the NOTIFICATION SETTINGS section.

  2. Enter the Legacy server key you noted down from the Google Firebase Console.

  3. Select Save on the toolbar.

Your notification hub is configured to work with FCM, and you have the connection strings to both register your app to receive notifications and to send push notifications.

Create a Xamarin.Android app and connect it to notification hub

Create Visual Studio project and add NuGet packages

  1. In Visual Studio, open the File menu, select New, and then select Project. In the New Project window, do these steps:

    1. Expand Installed, Visual C#, and then click Android.

    2. Select Android App (Xamarin) from the list.

    3. Enter a name for the project.

    4. Select a location for the project.

    5. Select OK

      New Project dialog

  2. On the New Android App dialog box, select Blank App, and select OK.

    New Project dialog

  3. In the Solution Explorer window, expand Properties, and click AndroidManifest.xml. Update the package name to match the package name you entered when adding Firebase Cloud Messaging to your project in the Google Firebase Console.

    Package name in GCM

  4. Right-click your project, and select Manage NuGet Packages....

  5. Select the Browse tab. Search for Xamarin.GooglePlayServices.Base. Select Xamarin.GooglePlayServices.Base in the result list. Then, select Install.

    Google Play Services NuGet

  6. In the NuGet Package Manager window, search for Xamarin.Firebase.Messaging. Select Xamarin.Firebase.Messaging in the result list. Then, select Install.

  7. Now, search for Xamarin.Azure.NotificationHubs.Android. Select Xamarin.Azure.NotificationHubs.Android in the result list. Then, select Install.

Add the Google Services JSON File

  1. Copy the google-services.json file that you downloaded from the Google Firebase Console to the project folder.

  2. Add google-services.json to the project.

  3. Select google-services.json in the Solution Explorer window.

  4. In the Properties pane, set the Build Action to GoogleServicesJson. If you don't see GoogleServicesJson, close Visual Studio, relaunch it, reopen the project, and retry.

    GoogleServicesJson build action

Set up notification hubs in your project

Registering with Firebase Cloud Messaging

  1. Open the AndroidManifest.xml file and insert the following <receiver> elements into the <application> element:

    <receiver android:name="com.google.firebase.iid.FirebaseInstanceIdInternalReceiver" android:exported="false" />
    <receiver android:name="com.google.firebase.iid.FirebaseInstanceIdReceiver" android:exported="true" android:permission="com.google.android.c2dm.permission.SEND">
        <intent-filter>
        <action android:name="com.google.android.c2dm.intent.RECEIVE" />
        <action android:name="com.google.android.c2dm.intent.REGISTRATION" />
        <category android:name="${applicationId}" />
        </intent-filter>
    </receiver>
    
  2. Add the following statements before the application element.

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS"/>
    
  3. Gather the following information for your Android app and notification hub:

    • Listen connection string: On the dashboard in the Azure portal, choose View connection strings. Copy the DefaultListenSharedAccessSignature connection string for this value.
    • Hub name: Name of your hub from the Azure portal. For example, mynotificationhub2.
  4. In the Solution Explorer window, right-click your project, select Add, and then select Class.

  5. Create a Constants.cs class for your Xamarin project and define the following constant values in the class. Replace the placeholders with your values.

    public static class Constants
    {
        public const string ListenConnectionString = "<Listen connection string>";
        public const string NotificationHubName = "<hub name>";
    }
    
  6. Add the following using statements to MainActivity.cs:

    using Android.Util;
    using Android.Gms.Common;
    
  7. Add the following properties to the MainActivity class. The TAG variable will be used to show an alert dialog when the app is running:

    public const string TAG = "MainActivity";
    internal static readonly string CHANNEL_ID = "my_notification_channel";
    
  8. Add the following method to the MainActivity class. It checks whether Google Play Services are available on the device.

    public bool IsPlayServicesAvailable()
    {
        int resultCode = GoogleApiAvailability.Instance.IsGooglePlayServicesAvailable(this);
        if (resultCode != ConnectionResult.Success)
        {
            if (GoogleApiAvailability.Instance.IsUserResolvableError(resultCode))
                Log.Debug(TAG, GoogleApiAvailability.Instance.GetErrorString(resultCode));
            else
            {
                Log.Debug(TAG, "This device is not supported");
                Finish();
            }
            return false;
        }
    
        Log.Debug(TAG, "Google Play Services is available.");
        return true;
    }
    
  9. Add the following method to the MainActivity class that creates a notification 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 channelName = CHANNEL_ID;
        var channelDescription = string.Empty;
        var channel = new NotificationChannel(CHANNEL_ID, channelName, NotificationImportance.Default)
        {
            Description = channelDescription
        };
    
        var notificationManager = (NotificationManager)GetSystemService(NotificationService);
        notificationManager.CreateNotificationChannel(channel);
    }
    
  10. In MainActivity.cs, add the following code to OnCreate after base.OnCreate(savedInstanceState):

    if (Intent.Extras != null)
    {
        foreach (var key in Intent.Extras.KeySet())
        {
            if(key!=null)
            {
                var value = Intent.Extras.GetString(key);
                Log.Debug(TAG, "Key: {0} Value: {1}", key, value);
            }
        }
    }
    
    IsPlayServicesAvailable();
    CreateNotificationChannel();
    
  11. Create a new class, MyFirebaseIIDService like you created the Constants class.

  12. Add the following using statements to MyFirebaseIIDService.cs:

    using Android.Util;
    using WindowsAzure.Messaging;
    using Firebase.Iid;
    
  13. In MyFirebaseIIDService.cs, add the following class declaration, and have your class inherit from FirebaseInstanceIdService:

    [Service]
    [IntentFilter(new[] { "com.google.firebase.INSTANCE_ID_EVENT" })]
    public class MyFirebaseIIDService : FirebaseInstanceIdService
    
  14. In MyFirebaseIIDService.cs, add the following code:

    const string TAG = "MyFirebaseIIDService";
    NotificationHub hub;
    
    public override void OnTokenRefresh()
    {
        var refreshedToken = FirebaseInstanceId.Instance.Token;
        Log.Debug(TAG, "FCM token: " + refreshedToken);
        SendRegistrationToServer(refreshedToken);
    }
    
    void SendRegistrationToServer(string token)
    {
        // Register with Notification Hubs
        hub = new NotificationHub(Constants.NotificationHubName,
                                    Constants.ListenConnectionString, this);
    
        var tags = new List<string>() { };
        var regID = hub.Register(token, tags.ToArray()).RegistrationId;
    
        Log.Debug(TAG, $"Successful registration of ID {regID}");
    }
    
  15. Create another new class for your project, name it MyFirebaseMessagingService.

  16. Add the following using statements to MyFirebaseMessagingService.cs.

    using Android.Util;
    using Firebase.Messaging;
    using Android.Support.V4.App;
    using Build = Android.OS.Build;
    
  17. Add the following above your class declaration, and have your class inherit from FirebaseMessagingService:

    [Service]
    [IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
    public class MyFirebaseMessagingService : FirebaseMessagingService
    
  18. Add the following code to MyFirebaseMessagingService.cs:

    const string TAG = "MyFirebaseMsgService";
    public override void OnMessageReceived(RemoteMessage message)
    {
        Log.Debug(TAG, "From: " + message.From);
        if(message.GetNotification()!= null)
        {
            //These is how most messages will be received
            Log.Debug(TAG, "Notification Message Body: " + message.GetNotification().Body);
            SendNotification(message.GetNotification().Body);
        }
        else
        {
            //Only used for debugging payloads sent from the Azure portal
            SendNotification(message.Data.Values.First());
    
        }
    }
    
    void SendNotification(string messageBody)
    {
        var intent = new Intent(this, typeof(MainActivity));
        intent.AddFlags(ActivityFlags.ClearTop);
        var pendingIntent = PendingIntent.GetActivity(this, 0, intent, PendingIntentFlags.OneShot);
    
        var notificationBuilder = new NotificationCompat.Builder(this)
                    .SetContentTitle("FCM Message")
                    .SetSmallIcon(Resource.Drawable.ic_launcher)
                    .SetContentText(messageBody)
                    .SetAutoCancel(true)
                    .SetShowWhen(false)
                    .SetContentIntent(pendingIntent);
    
        if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
        {
            notificationBuilder.SetChannelId(MainActivity.CHANNEL_ID);
        }
    
        var notificationManager = NotificationManager.FromContext(this);
    
        notificationManager.Notify(0, notificationBuilder.Build());
    }
    
  19. Build your project.

  20. Run your app on your device or loaded emulator

Send test notification from the Azure portal

You can test receiving notifications in your app with the Test Send option in the Azure portal. It sends a test push notification to your device.

Azure portal - Test Send

Push notifications are normally sent in a back-end service like Mobile Services or ASP.NET through a compatible library. If a library is not available for your back-end, you can also use the REST API directly to send notification messages.

Next steps

In this tutorial, you sent broadcast notifications to all your Android devices registered with the backend. To learn how to push notifications to specific Android devices, advance to the following tutorial: