MapKit 中的沿线注释

使用MapKit中的沿线注释可以在地图上显示沿线的标注信息，为用户提供更丰富的地图体验。沿线注释可以用于显示沿线的景点、商铺、交通信息等，帮助用户更好地了解周围环境。下面将介绍如何使用MapKit中的沿线注释，并给出一个案例代码。

swift
import MapKit
class ViewController: UIViewController, MKMapViewDelegate {
    @IBOutlet weak var mapView: MKMapView!
    override func viewDidLoad() {
        super.viewDidLoad()
        
        mapView.delegate = self
        
        let coordinates = [
            CLLocationCoordinate2D(latitude: 37.331705, longitude: -122.030237),
            CLLocationCoordinate2D(latitude: 37.332465, longitude: -122.029664),
            CLLocationCoordinate2D(latitude: 37.332792, longitude: -122.028902),
            CLLocationCoordinate2D(latitude: 37.333378, longitude: -122.028253),
            CLLocationCoordinate2D(latitude: 37.334036, longitude: -122.027717)
        ]
        
        let polyline = MKPolyline(coordinates: coordinates, count: coordinates.count)
        mapView.addOverlay(polyline)
        
        let renderer = MKPolylineRenderer(polyline: polyline)
        renderer.lineWidth = 3.0
        renderer.strokeColor = UIColor.blue
        mapView.addOverlay(renderer.polyline)
        
        let annotation1 = MKPointAnnotation()
        annotation1.coordinate = CLLocationCoordinate2D(latitude: 37.332465, longitude: -122.029664)
        annotation1.title = "Apple Campus"
        annotation1.subtitle = "Headquarters of Apple Inc."
        
        let annotation2 = MKPointAnnotation()
        annotation2.coordinate = CLLocationCoordinate2D(latitude: 37.333378, longitude: -122.028253)
        annotation2.title = "Googleplex"
        annotation2.subtitle = "Headquarters of Google Inc."
        
        mapView.addAnnotations([annotation1, annotation2])
    }
    func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
        if overlay is MKPolyline {
            let renderer = MKPolylineRenderer(overlay: overlay)
            renderer.lineWidth = 3.0
            renderer.strokeColor = UIColor.blue
            return renderer
        }
        
        return MKOverlayRenderer(overlay: overlay)
    }
}

swift
func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    if annotation is MKPointAnnotation {
        let identifier = "AnnotationIdentifier"
        
        var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: identifier)
        
        if annotationView == nil {
            annotationView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier)
            annotationView?.canShowCallout = true
        } else {
            annotationView?.annotation = annotation
        }
        
        return annotationView
    }
    
    return nil
}