Question

我在地图上显示注释时遇到问题。它们仅在我移动或拖动地图时显示。

我试图遵循youtube上的教程以及c尖锐的问题之一

请给我一个帮助..这是代码

在这里我为注释创建了一个类

  class customPin: NSObject, MKAnnotation {
    var coordinate: CLLocationCoordinate2D
    var title: String?
    var subtitle: String?

    init(pinTitle:String, pinSubTitle:String, location:CLLocationCoordinate2D) {
        self.title = pinTitle
        self.subtitle = pinSubTitle
        self.coordinate = location
    }}

    class ViewController: UIViewController, CLLocationManagerDelegate {

    @IBOutlet weak var mapView: MKMapView!

     var locationManager = CLLocationManager()

    override func viewDidLoad() {
        super.viewDidLoad()

        mapView.register(CustomAnnotationView.self, forAnnotationViewWithReuseIdentifier: MKMapViewDefaultAnnotationViewReuseIdentifier)

        self.locationManager.requestWhenInUseAuthorization()


        //json show the list of the parks


pipiCanList()

     //show location Barcelona
    let location = CLLocationCoordinate2D(latitude: 41.3851   , longitude:2.1734)
    let region = MKCoordinateRegion(center: location, span: MKCoordinateSpan(latitudeDelta: 0.05, longitudeDelta: 0.05))

    self.mapView.setRegion(region, animated: true)
    self.mapView.delegate = self

}

获取json信息

 func pipiCanList(){

        let url = "http://bluewave.lk/Apps/pipiCan/Api/read.php";
        let urlObj = URL(string:url);

        URLSession.shared.dataTask(with: urlObj!) {(data, response, error) in
            do{
                let pipiCans = try JSONDecoder().decode([pipiCanDBList].self, from: data!)

                for pipiCan in pipiCans{

                    let Latitude = (pipiCan.ParkLatitude! as NSString).doubleValue
                    let Longitude = (pipiCan.ParkLongitude! as NSString).doubleValue
                    let  location = CLLocationCoordinate2D(latitude: Latitude, longitude: Longitude)

                    //add to
                    let pin = customPin(pinTitle: pipiCan.ParkName!, pinSubTitle: pipiCan.Area!, location:  location)
                    self.mapView.addAnnotation(pin)

                  }
            } catch{

                print ("Error - cannot get list")

            }
            }.resume()


    }
}

Answer 1

您需要

DispatchQueue.main.async { 
    let pin = customPin(pinTitle: pipiCan.ParkName!, pinSubTitle: pipiCan.Area!, location:  location)
    self.mapView.addAnnotation(pin)
}

由于URLSession.shared.dataTask回调位于后台线程中，因此您应该在主线程中访问诸如mapView之类的 UIKit 元素。您也可以

self.mapView.showAnnotations(self.mapView.annotations, animated: true)

在显示所有已添加注释的for循环之后，请记住在此处设置区域

 let location = CLLocationCoordinate2D(latitude: 41.3851   , longitude:2.1734)
let region = MKCoordinateRegion(center: location, span: MKCoordinateSpan(latitudeDelta: 0.05, longitudeDelta: 0.05))

响应可能具有比上述区域远的位置值

在用户在地图上拖动之前，无法看到来自json的swift 4注解

1 个答案: