public override void OnAppearing()
        {
            base.OnAppearing();

            locationManager.AddLocationListener(this);
            nearbyExhibitManager.ExhibitVisitedEvent += ExhibitVisited;
        }
        /// <summary>
        /// Called when the view was added to the visual tree.
        /// </summary>
        public override void OnAppearing()
        {
            base.OnAppearing();

            locationManager.AddLocationListener(this);
        }