为什么我无法在 iOS 上的地图图钉中添加两个字段 - xamarin

我CustomMapRenderer在 iOS 项目上有 e ，我想在标记单击中再添加两个字段。

在CustomMKAnnotationView.cs我创建了另外两个对象 -CodeNum和AlertLevel：

    using MapKit;

namespace MaritsaTundzhaForecast.iOS
{
    public class CustomMKAnnotationView : MKAnnotationView
    {
        public string Name { get; set; }

        public string Url { get; set; }

        public int AlertLevel { get; set; }

        public int CodeNum { get; set; }

        public CustomMKAnnotationView(IMKAnnotation annotation, string id)
            : base(annotation, id)
        {
        }
    }
}

在CustomMapRenderer.cs我使用这行代码来显示它但是当我点击 pin 时它们不会出现：

((CustomMKAnnotationView)annotationView).AlertLevel = customPin.AlertLevel;
((CustomMKAnnotationView)annotationView).CodeNum = customPin.CodeNum;

这是完整的代码GetViewForAnnotation：

 protected override MKAnnotationView GetViewForAnnotation(MKMapView mapView, IMKAnnotation annotation)
    {
        MKAnnotationView annotationView = null;

        if (annotation is MKUserLocation)
            return null;

        var customPin = GetCustomPin(annotation as MKPointAnnotation);
        if (customPin == null)
        {
            throw new Exception("Custom pin not found");
        }

        annotationView = mapView.DequeueReusableAnnotation(customPin.Name);
        if (annotationView == null)
        {
            annotationView = new CustomMKAnnotationView(annotation, customPin.Name);
            annotationView.Image = UIImage.FromFile("pin.png");
            annotationView.CalloutOffset = new CGPoint(0, 0);
            annotationView.LeftCalloutAccessoryView = new UIImageView(UIImage.FromFile("green.png"));
            
            ((CustomMKAnnotationView)annotationView).Name = customPin.Name;
            ((CustomMKAnnotationView)annotationView).Url = customPin.Url;
            ((CustomMKAnnotationView)annotationView).AlertLevel = customPin.AlertLevel;
            ((CustomMKAnnotationView)annotationView).CodeNum = customPin.CodeNum;
        }
        annotationView.CanShowCallout = true;

        return annotationView;
    }

我有OnDidSelectAnnotation方法，但我不知道在里面写什么来显示CodeNum和AlertLevel：

void OnDidSelectAnnotationView(object sender, MKAnnotationViewEventArgs e)
    {
        CustomMKAnnotationView customView = e.View as CustomMKAnnotationView;
        customPinView = new UIView();

        if (customView.Name.Equals("Xamarin"))
        {
            customPinView.Frame = new CGRect(0, 0, 200, 84);
            /*
            var image = new UIImageView(new CGRect(0, 0, 200, 84));
            image.Image = UIImage.FromFile("green.png");
            customPinView.AddSubview(image);
            */
            customPinView.Center = new CGPoint(0, -(e.View.Frame.Height + 75));
            e.View.AddSubview(customPinView);
        }
    }

    void OnDidDeselectAnnotationView(object sender, MKAnnotationViewEventArgs e)
    {
        if (!e.View.Selected)
        {
            customPinView.RemoveFromSuperview();
            customPinView.Dispose();
            customPinView = null;
        }
    }