如何在Swift 5中使用MapKit仅显示城市

import MapKit

var mapView: MKMapView!
mapView = MKMapView(frame: view.bounds)
mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
view.addSubview(mapView)

let geocoder = CLGeocoder()
geocoder.geocodeAddressString("城市名称") { (placemarks, error) in
    if let placemark = placemarks?.first {
        let location = placemark.location
        // 在地图上添加一个标注点
        let annotation = MKPointAnnotation()
        annotation.coordinate = location!.coordinate
        self.mapView.addAnnotation(annotation)
        // 设置地图显示区域和缩放级别
        let region = MKCoordinateRegion(center: annotation.coordinate, latitudinalMeters: 10000, longitudinalMeters: 10000)
        self.mapView.setRegion(region, animated: true)
    }
}