在viewDidLoad中获取位置

Question

I am trying to get the user location but it doesn't work when the view loads. I have a refresh method that works just fine but that requires the user to tap a refresh button. The user location appears on the map when the view loads but in getLocation(), myLocation is nil. And again, tapping the refresh button that calls refreshLocation() works as expected.

override func viewDidLoad() {
        super.viewDidLoad()

        locationManager = CLLocationManager()
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyKilometer

        mapView.userTrackingMode = .follow

        getLocationAuthorizationStatus()
    }

Request Authorization

func getLocationAuthorizationStatus() {
        print("getLocationAuthorizationStatus()")
        if CLLocationManager.authorizationStatus() == .notDetermined {
            locationManager.requestWhenInUseAuthorization()
        } else if CLLocationManager.authorizationStatus() == .denied {
            // Display UIAlertController
            let locationDeniedAlert = BasicAlert(title: "", message: "Location services were denied. Please enable location services in Settings.", preferredStyle: .alert)

            let settingsAction = UIAlertAction(title: "Settings", style: .default, handler: {
                (action) -> Void in
                let settingsURL = URL(string: UIApplicationOpenSettingsURLString)
                if let url = settingsURL {
                    // UIApplication.shared.openURL(url)
                    UIApplication.shared.open(url, options: [:], completionHandler: nil)
                }

                locationDeniedAlert.dismiss(animated: true, completion: nil)
            })

            locationDeniedAlert.addAction(settingsAction)

            self.present(locationDeniedAlert, animated: true, completion: nil)

        } else if CLLocationManager.authorizationStatus() == .authorizedWhenInUse {
            if fromSearch {
                fromSearch = false
            } else {
                getLocation()
            }
        }
    }

Get Location

func getLocation() {
        print("getLocation()")
        locationManager.startUpdatingLocation()

        if locationManager.location != nil {
            myLocation = locationManager.location!
            if mapView.annotations.count == 1 && mapView.annotations[0] as! MKUserLocation == mapView.userLocation {
                retrieveGymsWithLocation()
            }
        } else {
            myLocation = nil
            print("location = nil")
        }
    }

    @objc func refreshLocation() {
        print("refreshLocation()")
        let annotationsToRemove = mapView.annotations
        mapView.removeAnnotations(annotationsToRemove)
        gyms.removeAll()
        imageArrays.removeAll()
        gymLocations.removeAll()

        getLocationAuthorizationStatus()
    }

Location Manager

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        manager.stopUpdatingLocation()
        myLocation = locations.last
    }

Answer 1

It takes a while for CLLocationManager to determine the current location, depending on gps satellite availability and other kinds of influence. Therefore, you'll simply have to wait a while until the location property is set. You typically would do this in the delegate method:

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    manager.stopUpdatingLocation()
    myLocation = locations.last

    if mapView.annotations.count == 1 && mapView.annotations[0] as! MKUserLocation == mapView.userLocation {
        retrieveGymsWithLocation()
    } 
}