如何在 Swift 中创建 MKCircle？

Question

我一直在四处寻找关于如何使用 Swift 2.0 为 MapView 制作 MKCircle 注释的很好的解释，但我似乎找不到足够的解释。有人可以发布一些示例代码来展示如何创建 MKCircle 注释吗？这是我用来制作地图并获取坐标的代码。

let address = self.location

let geocoder = CLGeocoder()

    geocoder.geocodeAddressString(address, completionHandler: {(placemarks, error) -> Void in
        if((error) != nil){
            print("Error", error)
        }
        if let placemark = placemarks?.first {
            let coordinates:CLLocationCoordinate2D = placemark.location!.coordinate

            self.locationCoordinates = coordinates
            let span = MKCoordinateSpanMake(0.005, 0.005)
            let region = MKCoordinateRegion(center: self.locationCoordinates, span: span)
            self.CIMap.setRegion(region, animated: true)

            let annotation = MKPointAnnotation()
            annotation.coordinate = self.locationCoordinates
            self.CIMap.addAnnotation(annotation)

            self.CIMap.layer.cornerRadius = 10.0

            self.CIMap.addOverlay(MKCircle(centerCoordinate: self.locationCoordinates, radius: 1000))
        }
    })

Answer 1

首先您需要将 MKMapViewDelegate 添加到类定义中。

 mapView.delegate = self 

在 viewDidLoad 中将地图委托设置为 self。

设置注释

mapView.addOverlay(MKCircle(centerCoordinate: CLLocationCoordinate2D, radius: CLLocationDistance))

mapView rendererForOverlay 现在应该在 mapViews 委托中调用，然后你就可以绘制它了

func mapView(mapView: MKMapView, rendererForOverlay overlay: MKOverlay) -> MKOverlayRenderer {
    if let overlay = overlay as? MKCircle {
        let circleRenderer = MKCircleRenderer(circle: overlay)
        circleRenderer.fillColor = UIColor.blueColor()
        return circleRenderer
    }
}

另外，你需要导入 MapKit 才能编译

Answer 2

将展示有关如何使用带有 xcode 8.3.3 的 swift 3 在地图视图上创建圆形叠加层的逐步方法

在您的主情节提要文件中，将地图套件视图拖到情节提要的场景（视图）并为其创建插座，这里我创建了 mapView。此外，您还想在地图上长按时动态创建叠加层，因此将 Long Press Gesture Recognizer 从对象库拖到 mapView 上，然后为其创建操作方法，这里我创建了 addRegion() 相同的方法。

1. 为 CLLocationManager 类创建一个全局常量，以便在每个函数中都可以访问它。在你的 viewDidLoad 方法中，添加一些代码来获得用户的授权。

       import UIKit  
       import MapKit
   
       class ViewController: UIViewController {
   
   
           @IBOutlet var mapView: MKMapView!
           let locationManager = CLLocationManager()
   
       override func viewDidLoad() {  
               super.viewDidLoad()
   
               locationManager.delegate = self
               locationManager.requestAlwaysAuthorization()
               locationManager.requestWhenInUseAuthorization()
               locationManager.desiredAccuracy = kCLLocationAccuracyBest
               locationManager.startUpdatingLocation()
   
           }
   

2. 在长按手势识别器操作方法 addRegion() 中添加用于在执行长按手势识别器时生成圆形区域的代码。

       @IBAction func addRegion(_ sender: Any) {  
               print("addregion pressed")  
               guard let longPress = sender as? UILongPressGestureRecognizer else {return}
   
               let touchLocation = longPress.location(in: mapView)
               let coordinates = mapView.convert(touchLocation, toCoordinateFrom: mapView)
               let region = CLCircularRegion(center: coordinates, radius: 5000, identifier: "geofence")
               mapView.removeOverlays(mapView.overlays)
               locationManager.startMonitoring(for: region)
               let circle = MKCircle(center: coordinates, radius: region.radius)
               mapView.add(circle)
   
           }
   

在地图上渲染圆圈之前，您仍然不会在地图上实际看到圆圈。为此，您需要实现 mapviewdelegate 的委托。

        func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {}

1. 为了使代码看起来更简洁，您可以在类结束的最后一个大括号之后创建扩展。一个扩展包含 CLLocationManagerDelegate 的代码和另一个 MKMapViewDelegate 的代码。

       extension ViewController: CLLocationManagerDelegate {
           func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
               locationManager.stopUpdatingLocation()
               mapView.showsUserLocation = true
           }
       }
   

你应该在委托方法中调用 locationManager.stopUpdatingLocation()，这样你的电池就不会耗尽。

        extension ViewController: MKMapViewDelegate {
            func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
                guard let circelOverLay = overlay as? MKCircle else {return MKOverlayRenderer()}

                let circleRenderer = MKCircleRenderer(circle: circelOverLay)
                circleRenderer.strokeColor = .blue
                circleRenderer.fillColor = .blue
                circleRenderer.alpha = 0.2
                return circleRenderer
            }
        }

我们在屏幕上画了一个真正的圆圈。

最终代码应如下所示。

import UIKit
import MapKit

class ViewController: UIViewController {


    @IBOutlet var mapView: MKMapView!
    let locationManager = CLLocationManager()

    override func viewDidLoad() {
        super.viewDidLoad()

        locationManager.delegate = self
        locationManager.requestAlwaysAuthorization()
        locationManager.requestWhenInUseAuthorization()
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.startUpdatingLocation()

    }

    // MARK: Long Press Gesture Recognizer Action Method

    @IBAction func addRegion(_ sender: Any) {
        print("addregion pressed")
        guard let longPress = sender as? UILongPressGestureRecognizer else {return}

        let touchLocation = longPress.location(in: mapView)
        let coordinates = mapView.convert(touchLocation, toCoordinateFrom: mapView)
        let region = CLCircularRegion(center: coordinates, radius: 5000, identifier: "geofence")
        mapView.removeOverlays(mapView.overlays)
        locationManager.startMonitoring(for: region)
        let circle = MKCircle(center: coordinates, radius: region.radius)
        mapView.add(circle)

    }

}

extension ViewController: CLLocationManagerDelegate {
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        locationManager.stopUpdatingLocation()
        mapView.showsUserLocation = true
    }
}

extension ViewController: MKMapViewDelegate {
    func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
        guard let circelOverLay = overlay as? MKCircle else {return MKOverlayRenderer()}

        let circleRenderer = MKCircleRenderer(circle: circelOverLay)
        circleRenderer.strokeColor = .blue
        circleRenderer.fillColor = .blue
        circleRenderer.alpha = 0.2
        return circleRenderer
    }
}

Answer 3

叠加层只是一组数字。在地图视图中可见的是一个叠加渲染器。您必须实现mapView:rendererForOverlay: 来提供覆盖渲染器；否则，您将什么也看不到。