Como usar notificações Push nos formulários Xamarin

Acabei de implementar a notificação push há alguns dias, e vou partilhar a minha solução aqui (com base em PushSharp)

Guia passo a passo:

1) no seu projecto partilhado, crie uma Interface chamada IPushNotificationRegister

public interface IPushNotificationRegister
{
    void ExtractTokenAndRegister();
}

Esta interface é usada para obter o item de envio e, em seguida, enviá-lo para o servidor. Este símbolo é único por dispositivo.

Implementação Android:

3) Adicionar receptores para ouvir eventos recebidos pelo serviço Google GCM:

A)

[BroadcastReceiver]
[IntentFilter(new[] { Intent.ActionBootCompleted })]
public class GCMBootReceiver : BroadcastReceiver
{
    public override void OnReceive(Context context, Intent intent)
    {
        MyIntentService.RunIntentInService(context, intent);
        SetResult(Result.Ok, null, null);
    }
}

B)

[assembly: Permission(Name = "@[email protected]_MESSAGE")]
[assembly: UsesPermission(Name = "android.permission.WAKE_LOCK")]
[assembly: UsesPermission(Name = "@[email protected]_MESSAGE")]
[assembly: UsesPermission(Name = "com.google.android.c2dm.permission.RECEIVE")]
[assembly: UsesPermission(Name = "android.permission.GET_ACCOUNTS")]
[assembly: UsesPermission(Name = "android.permission.INTERNET")]

namespace Consumer.Mobile.Droid.PushNotification
{
    [BroadcastReceiver(Permission = "com.google.android.c2dm.permission.SEND")]
    [IntentFilter(new string[] { "com.google.android.c2dm.intent.RECEIVE" }, Categories = new string[] { "@PACKAGE_NAME@" })]
    [IntentFilter(new string[] { "com.google.android.c2dm.intent.REGISTRATION" }, Categories = new string[] { "@PACKAGE_NAME@" })]
    [IntentFilter(new string[] { "com.google.android.gcm.intent.RETRY" }, Categories = new string[] { "@PACKAGE_NAME@" })]
    [IntentFilter (new[]{ Intent.ActionBootCompleted }, Categories = new[]{ Intent.CategoryDefault })]
    public class GCMBroadcastReceiver : BroadcastReceiver
    {
        public override void OnReceive(Context context, Intent intent)
        {
            MyIntentService.RunIntentInService(context, intent);
            SetResult(Result.Ok, null, null);
        }
    }
}

Adicionar um serviço de intenção para processar a notificação

using Android.App;
using Android.Content;
using Android.Graphics;
using Android.Media;
using Android.OS;
using Android.Support.V4.App;
using Consumer.Mobile.Infra;
using Consumer.Mobile.Services.PushNotification;
using Java.Lang;
using XLabs.Ioc;
using TaskStackBuilder = Android.Support.V4.App.TaskStackBuilder;

namespace Consumer.Mobile.Droid.PushNotification
{
    [Service]
    public class MyIntentService : IntentService
    {
        private readonly ILogger _logger;
        private readonly IPushNotificationService _notificationService;
        private readonly IPushNotificationRegister _pushNotificationRegister;

        public MyIntentService()
        {
            _logger = Resolver.Resolve<ILogger>();
            _notificationService = Resolver.Resolve<IPushNotificationService>();
            _pushNotificationRegister = Resolver.Resolve<IPushNotificationRegister>();
        }

        static PowerManager.WakeLock _sWakeLock;
        static readonly object Lock = new object();


        public static void RunIntentInService(Context context, Intent intent)
        {
            lock (Lock)
            {
                if (_sWakeLock == null)
                {
                    // This is called from BroadcastReceiver, there is no init.
                    var pm = PowerManager.FromContext(context);
                    _sWakeLock = pm.NewWakeLock(
                    WakeLockFlags.Partial, "My WakeLock Tag");
                }
            }

            _sWakeLock.Acquire();
            intent.SetClass(context, typeof(MyIntentService));
            context.StartService(intent);
        }

        protected override void OnHandleIntent(Intent intent)
        {
            try
            {
                Context context = this.ApplicationContext;
                string action = intent.Action;

                if (action.Equals("com.google.android.c2dm.intent.REGISTRATION"))
                {
                    HandleRegistration(context, intent);
                }
                else if (action.Equals("com.google.android.c2dm.intent.RECEIVE"))
                {
                    HandleMessage(context, intent);
                }
            }
            finally
            {
                lock (Lock)
                {
                    //Sanity check for null as this is a public method
                    if (_sWakeLock != null)
                        _sWakeLock.Release();
                }
            }
        }

        private void HandleMessage(Context context, Intent intent)
        {

            Intent resultIntent = new Intent(this, typeof(MainActivity));


            TaskStackBuilder stackBuilder = TaskStackBuilder.Create(this);

            var c = Class.FromType(typeof(MainActivity));
            stackBuilder.AddParentStack(c);
            stackBuilder.AddNextIntent(resultIntent);

            string alert = intent.GetStringExtra("Alert");
            int number = intent.GetIntExtra("Badge", 0);

            var imageUrl = intent.GetStringExtra("ImageUrl");
            var title = intent.GetStringExtra("Title");

            Bitmap bitmap = GetBitmap(imageUrl);

            PendingIntent resultPendingIntent = stackBuilder.GetPendingIntent(0, (int)PendingIntentFlags.UpdateCurrent);

            NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
                .SetAutoCancel(true) // dismiss the notification from the notification area when the user clicks on it
                .SetContentIntent(resultPendingIntent) // start up this activity when the user clicks the intent.
                .SetContentTitle(title) // Set the title
                .SetNumber(number) // Display the count in the Content Info
                .SetSmallIcon(Resource.Drawable.Icon) // This is the icon to display
                .SetLargeIcon(bitmap)
                .SetSound(RingtoneManager.GetDefaultUri(RingtoneType.Notification))
                .SetContentText(alert); // the message to display.

            // Build the notification:
            Notification notification = builder.Build();

            // Get the notification manager:
            NotificationManager notificationManager =
                GetSystemService(Context.NotificationService) as NotificationManager;

            // Publish the notification:
            const int notificationId = 0;
            notificationManager.Notify(notificationId, notification);
        }

        private void HandleRegistration(Context context, Intent intent)
        {
            var token = intent.GetStringExtra("registration_id");
            _logger.Info(this.Class.SimpleName, "Received Token : " + token);

            if (_pushNotificationRegister.ShouldSendToken(token))
            {
                var uid = Android.Provider.Settings.Secure.GetString(MainActivity.Context.ContentResolver, Android.Provider.Settings.Secure.AndroidId);
                _notificationService.AddPushToken(token, DeviceUtils.GetDeviceType(), uid);
            }
        }


        private Bitmap GetBitmap(string url)
        {

            try
            {
                System.Net.WebRequest request =
                    System.Net.WebRequest.Create(url);
                System.Net.WebResponse response = request.GetResponse();
                System.IO.Stream responseStream =
                    response.GetResponseStream();
                return BitmapFactory.DecodeStream(responseStream);


            }
            catch (System.Net.WebException)
            {
                return null;
            }

        }

    }
}

D) implementar a Interface IPushNotificationRegister:

using Android.App;
using Android.Content;
using Consumer.Mobile.Services;
using Consumer.Mobile.Services.PushNotification;
[assembly: Permission(Name = "@[email protected]_MESSAGE")]
[assembly: UsesPermission(Name = "@[email protected]_MESSAGE")]

// Gives the app permission to register and receive messages.
[assembly: UsesPermission(Name = "com.google.android.c2dm.permission.RECEIVE")]

// Needed to keep the processor from sleeping when a message arrives
[assembly: UsesPermission(Name = "android.permission.WAKE_LOCK")]
[assembly: UsesPermission(Name = "android.permission.RECEIVE_BOOT_COMPLETED")]
namespace Consumer.Mobile.Droid.PushNotification
{
    public class PushNotificationRegister : IPushNotificationRegister
    {          
        public override void ExtractTokenAndRegister()
        {
            string senders = AndroidConfig.GCMSenderId;
            Intent intent = new Intent("com.google.android.c2dm.intent.REGISTER");
            intent.SetPackage("com.google.android.gsf");
            intent.PutExtra("app", PendingIntent.GetBroadcast(MainActivity.Context, 0, new Intent(), 0));
            intent.PutExtra("sender", senders);
            MainActivity.Context.StartService(intent);
        }


    }
}

Implementação do IOS:

4) no seu AppDelegate, Adicione o seguinte método:

A)

public override void RegisteredForRemoteNotifications(UIApplication application, NSData deviceToken)
{
    var deviceTokenString = deviceToken.ToString().Replace("<","").Replace(">", "").Replace(" ", "");
    var notificationService = Resolver.Resolve<IPushNotificationService>();
    var pushNotificationRegister = Resolver.Resolve<IPushNotificationRegister>();

    if (pushNotificationRegister.ShouldSendToken(deviceTokenString))
    {
        var uid = UIDevice.CurrentDevice.IdentifierForVendor.AsString();
        notificationService.AddPushToken(deviceTokenString, DeviceUtils.GetDeviceType(), uid);
    }
}

B) Implementar IPushNotificationRegister :

using Consumer.Mobile.Services;
using Consumer.Mobile.Services.PushNotification;
using UIKit;

namespace Consumer.Mobile.iOS.PushNotification
{
    public class iOSPushNotificationRegister : IPushNotificationRegister
    {
        public override void ExtractTokenAndRegister()
        {
            const UIRemoteNotificationType notificationTypes = UIRemoteNotificationType.Alert | UIRemoteNotificationType.Badge | UIRemoteNotificationType.Sound;
            UIApplication.SharedApplication.RegisterForRemoteNotificationTypes(notificationTypes);
        }
    }
}