Question

我从情节提要中获得了mapView，并且一切正常，除了一件事：我从RESTful调用中添加并添加到地图中的注释mapView.addAnnotation（）直到我触摸并移动地图时才会显示在地图上地图。以下是相关代码：

class ViewController: UIViewController, MKMapViewDelegate {
    @IBOutlet weak var mapView: MKMapView!

    override func viewDidLoad() {
       super.viewDidLoad()
       self.mapView.delegate = self

       // API Call
       URLSession.shared.dataTask(with: mRequest) {
       (data, response, error) in do {

           let data = data

       ...

          let annotation = MKPointAnnotation()
          annotation.coordinate = CLLocationCoordinate2DMake(lat!, lon!)
          annotation.title = name as? String
          annotation.subtitle = details as? String
          self.mapView.addAnnotation(annotation)

       }
       ...
       }.resume()

    }
  }

Answer 1

问题是您正在从后台线程更新UI。由于dataTask完成，因此将在其中添加注释的块发生在后台。将注释代码包装在DispatchQueue.main.async { }块中，您应该会看到注释显示得很好。

DispatchQueue.main.async{
      let annotation = MKPointAnnotation()
      annotation.coordinate = CLLocationCoordinate2DMake(lat!, lon!)
      annotation.title = name as? String
      annotation.subtitle = details as? String
      self.mapView.addAnnotation(annotation)
}

mapView.addAnnotation（）直到触摸地图后才向地图添加图钉

1 个答案: