swift - Swift 4添加注释错误意外地在展开时发现了nil

我只是想在我的地图视图中添加注释，但是我一直遇到这个错误“在解包时意外地发现了零”，而且我似乎无法解决它，也找不到适合我的解决方案。有人能告诉我哪里出了问题吗？事先谢谢。我已经试过将var mapView: MKMapView!改为var mapView: MKMapView?，但没有成功

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
}
}

var mapView: MKMapView!
var locationManager = CLLocationManager()

override func viewDidLoad() {
    super.viewDidLoad()

    let location = CLLocationCoordinate2D(latitude: 32.2325, longitude:76.3242)
    let region = MKCoordinateRegion(center: location, span: MKCoordinateSpan(latitudeDelta: 0.005, longitudeDelta: 0.005))
    self.mapView.setRegion(region, animated: true)

    let pin = customPin(pinTitle: "Honory Dalailama Temple", pinSubTitle: "Dharamshala, Himachal Pradesh, India", location: location)
    self.mapView.addAnnotation(pin)
    self.mapView.delegate = self
}


func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    if annotation is MKUserLocation {
        return nil
    }

    let annotationView = MKAnnotationView(annotation: annotation, reuseIdentifier: "customannotation")
    annotationView.image = UIImage(named:"pin")
    annotationView.canShowCallout = true
    return annotationView
}

func mapView(_ mapView: MKMapView, didSelect view: MKAnnotationView) {
    print("annotation title == \(String(describing: view.annotation?.title!))")
}

fileprivate func setupLocationManager() {self.locationManager.requestWhenInUseAuthorization()

    if CLLocationManager.locationServicesEnabled() == true {

        if CLLocationManager.authorizationStatus() == .restricted || CLLocationManager.authorizationStatus() == .denied || CLLocationManager.authorizationStatus() == .notDetermined {

            locationManager.requestWhenInUseAuthorization()
        }

        locationManager.desiredAccuracy = 1.0
        locationManager.delegate = self
        locationManager.startUpdatingLocation()

    } else {
        print("PLease turn on location services or GPS")
    }

}

fileprivate func setupMapView() {
    let mView = MKMapView(frame: CGRect(x: 0, y: 20, width: view.frame.width, height: view.frame.height))
    mView.showsUserLocation = true
    view.addSubview(mView)
    mView.showsScale = true
    mView.showsPointsOfInterest = true
    mView.showsTraffic = true
    mView.showsCompass = true
    mView.userTrackingMode = .follow
    self.mapView = mView
}

}

最佳答案

这看起来像马车：
print("annotation title == \(String(describing: view.annotation?.title!))")
如果annotation为零，则强制使用!打开它，这将导致崩溃。
改为使用：
print("annotation title == \(String(describing: view.annotation?.title))")
还不清楚您是否在调用setupMapView()之前调用了mapView并实际设置了viewDidLoad()。在viewDidLoad()中添加行：
if mapView == nil { setupMapView() }
在使用mapView之前。

关于swift - Swift 4添加注释错误意外地在展开时发现了nil，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/54565895/