ios - myLocationEnabled - 展开时意外发现 nil

Question

我只是尝试使用 GoogleMaps API 获取 MapViewController 中的用户位置。我环顾四周，无法弄清楚为什么我不断收到 fatal error :在这个特定位置展开时意外发现 nil 和可选值。

这是我的代码:

class MapViewController: UIViewController {

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

    override func viewDidLoad() {
        super.viewDidLoad()

        locationManager.delegate = self
        locationManager.requestWhenInUseAuthorization()

        let camera = GMSCameraPosition.cameraWithLatitude(-34.9290, longitude:138.6010, zoom:10)
        let mapView = GMSMapView.mapWithFrame(CGRectZero, camera:camera)
        mapView.mapType = kGMSTypeNormal
        print("Calling addMarker")
        // addMarker()
        self.view = mapView
        }

extension MapViewController: CLLocationManagerDelegate {
    func locationManager(manager: CLLocationManager, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
        if status == .AuthorizedWhenInUse {
            locationManager.startUpdatingLocation()
            mapView.myLocationEnabled = true
            mapView.settings.myLocationButton = true
        }
    }

    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        if let location = locations.first {
            mapView.camera = GMSCameraPosition(target: location.coordinate, zoom: 15, bearing: 0, viewingAngle: 0)
            locationManager.stopUpdatingLocation()
        }
    }
}

这是我收到错误的地方:

!( http://imgur.com/qxxf0SV )

我知道 mapView.myLocationEnabled 返回 nil，但不明白为什么/如何。

Answer 1

很可能是mapView为零，而不是mapView.myLocationEnabled。当您遇到崩溃时，请尝试以下 lldb 命令:

po mapView

这会准确地告诉你。

didChangeAuthorizationStatus 委托(delegate)可能是在后台或在 View 完成之前调用的。您应该将这些扩展移至您的 AppDelegate 中。