Xamarin Forms Background Service For Data Sync Even If App Closes

Question

I Want to create a service which run's in background even if my app closes for data sync of Sqlite and mysql.

i have tried some methods but unable to achieve my goal.

if anyone can give me a sample app which runs a service in the background even if app close

Thanks

Answer 1

If you want to run your background functionality even after your app closes in certain interval, we need to create a foreground service. I am talking about android.

Firstly create a service class in Android project folder.Here I am creating a service named SqlService.

  [Service]
    class SqlService : Service
    {
        internal static readonly string CHANNEL_ID = "my_notification_channel";
        internal static readonly int NOTIFICATION_ID = 100;
        public override IBinder OnBind(Intent intent)
        {
            return null;
        }
        /*
         * This service will run until stopped explicitly because we are returning sticky
         */
        public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
        {
            Toast.MakeText(this, "Service started", ToastLength.Long).Show();
            StartServiceInForeground();
            return StartCommandResult.Sticky;
        }
        /*
         * When our service is to be destroyed, show a Toast message before the destruction.
         */
        public override void OnDestroy()
        {
            base.OnDestroy();
            Toast.MakeText(this, "Syncing stopped", ToastLength.Long).Show();
        }

        void StartServiceInForeground()
        {

            if (Build.VERSION.SdkInt >= BuildVersionCodes.O)
            {
                var intent = new Intent(this, typeof(MainActivity));

                var channel = new NotificationChannel(CHANNEL_ID, "Service Channel", NotificationImportance.High)
                {
                    Description = "Foreground Service Channel"
                };

                var notificationManager = (NotificationManager)GetSystemService(NotificationService);
                notificationManager.CreateNotificationChannel(channel);
                var pendingIntent = PendingIntent.GetActivity(this, MainActivity.NOTIFICATION_ID, intent, PendingIntentFlags.Immutable);
                var notification = new Notification.Builder(this, CHANNEL_ID)
                .SetContentTitle("My Sql App")
                .SetContentText("Sql Sync is on")
                .SetContentIntent(pendingIntent)
                .SetSmallIcon(Resource.Drawable.sr_notification)                
                .SetOngoing(true)
                .Build();
                 StartForeground(NOTIFICATION_ID, notification);
            }



            Device.StartTimer(TimeSpan.FromSeconds(300),  () =>
            {

                try
                {

                  //.. Do your sql syncing here 

                }

                catch (Exception ex)
                {

                }
                return true;
            });
        }

    }

In your MainActivity, you can start the service by using messeging center call from shared project.We also need to create a Notification channel.

Add this in your MainActivity

 public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
    {       
        internal static readonly string CHANNEL_ID = "my_notification_channel";
        internal static readonly int NOTIFICATION_ID = 100;

       protected override void OnCreate(Bundle savedInstanceState)
        {       
            base.OnCreate(savedInstanceState);         
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            LoadApplication(new App());
            CreateNotificationChannel();
            loadservice();      
        }




            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(CHANNEL_ID, "FCM Notifications", NotificationImportance.Default)
            {
                Description = "Firebase Cloud Messages appear in this channel",
            };
            channel.EnableVibration(true);
            channel.EnableLights(true);

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


            private void loadservice()
        {

            MessagingCenter.Subscribe<Object>(this, "StartLongRunningTaskMessage", (sender) => {
                Intent myIntent = new Intent(this, typeof(LocationService));
                this.StartService(myIntent);
            });

            MessagingCenter.Subscribe<Object>(this, "StopLongRunningTaskMessage", (sender) => {
                Intent myIntent = new Intent(this, typeof(LocationService));
                this.StopService(myIntent);
            });
        }
}

Now you can Start the service from your shared Project like, Lets say on a Button click.

  private async void Sync_Clicked(object sender, EventArgs e)
    {
     MessagingCenter.Send<Object>(new Object(), "StartLongRunningTaskMessage");     
    }

Also we can stop the service on another button click like:

  private async void Sync_Clicked(object sender, EventArgs e)
        {
         MessagingCenter.Send<Object>(new Object(), "StopLongRunningTaskMessage");      
        }

Revert back if you have any doubts.