MapView viewForAnnotation在圆圈中显示白色大头针(默认)

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    if annotation is MKUserLocation {
        return nil
    }
    
    let annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: "CustomAnnotationView") as? MKPinAnnotationView ?? MKPinAnnotationView(annotation: annotation, reuseIdentifier: "CustomAnnotationView")
    
    annotationView.pinTintColor = .white
    annotationView.canShowCallout = true
    
    // Add a circle overlay
    let circle = MKCircle(center: annotation.coordinate, radius: 50)
    mapView.addOverlay(circle)
    
    return annotationView
}

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is MKCircle {
        let renderer = MKCircleRenderer(overlay: overlay)
        renderer.fillColor = UIColor.blue.withAlphaComponent(0.2)
        renderer.strokeColor = UIColor.blue
        renderer.lineWidth = 1
        return renderer
    }
    return MKOverlayRenderer(overlay: overlay)
}