Android Xamarin - Closed App Notification

I'd like to create notificiation in my app, which is going to be showed in 10 seconds. It works well, when application is running, but when I close the application, notification is

Solution 1:

you can try this.

protectedoverridevoidOnDestroy()
        {
       Notificator not = new Notificator();
        not.ShowNotification(this);  
            base.OnDestroy();
        }

Solution 2:

You should keep your service alive when you destroy your application.

1. add return StartCommandResult.Sticky; in the OnStartCommand method.
2. start the service OnTaskRemoved function.

Create your service with the Service interface, the IntentService is for Time-consuming operation.

classNotifyEvent : Service
    {
        [return: GeneratedEnum]
        publicoverride StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
        {
            new Task(() => {

                PendingIntent pIntent = PendingIntent.GetActivity(this, 0, intent, 0);
                Notification.Builder builder = new Notification.Builder(this);
                builder.SetContentTitle("hello");
                builder.SetContentText("hello");
                builder.SetSmallIcon(Resource.Drawable.Icon);
                builder.SetPriority(1);
                builder.SetDefaults(NotificationDefaults.Sound | NotificationDefaults.Vibrate);
                builder.SetWhen(Java.Lang.JavaSystem.CurrentTimeMillis());
                Notification notifikace = builder.Build();
                NotificationManager notificationManager = GetSystemService(Context.NotificationService) as NotificationManager;
                constint notificationId = 0;
                notificationManager.Notify(notificationId, notifikace);

            }).Start();
            return StartCommandResult.Sticky;
        }

        publicoverride IBinder OnBind(Intent intent)
        {
            returnnull;
        }
        publicoverridevoidOnTaskRemoved(Intent rootIntent)
        {
            Intent restartService = new Intent(ApplicationContext, typeof(NotifyEvent));
            restartService.SetPackage(PackageName);
            var pendingServiceIntent = PendingIntent.GetService(ApplicationContext, 0, restartService, PendingIntentFlags.UpdateCurrent);
            AlarmManager alarm = (AlarmManager)ApplicationContext.GetSystemService(Context.AlarmService);
            alarm.Set(AlarmType.ElapsedRealtime, SystemClock.ElapsedRealtime() + 1000, pendingServiceIntent);

            System.Console.WriteLine("service OnTaskRemoved");
            base.OnTaskRemoved(rootIntent);
        }
    }