我正在开发一个小型地图应用程序,该应用程序允许用户查看其当前位置。我有执行此操作的相关代码,它似乎按预期工作:
import UIKit
import MapKit
import CoreLocation
class ViewController: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate, UISearchBarDelegate, UIPopoverPresentationControllerDelegate {
// CLlocation
var location: CLLocation!
let locationManager = CLLocationManager()
// Map variables
var searchController:UISearchController!
var annotation:MKAnnotation!
var localSearchRequest:MKLocalSearchRequest!
var localSearch:MKLocalSearch!
var localSearchResponse:MKLocalSearchResponse!
var error:NSError!
var pointAnnotation:MKPointAnnotation!
var pinAnnotationView:MKPinAnnotationView!
// IBOutlets
@IBOutlet weak var placesMap: MKMapView!
// Location function
func locationManager(manager: CLLocationManager, didUpdateqLocations locations: [CLLocation]) {
let location = locations.last
let center = CLLocationCoordinate2D(latitude: location!.coordinate.latitude, longitude: location!.coordinate.longitude)
let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))
self.placesMap.setRegion(region, animated: true)
self.locationManager.stopUpdatingLocation()
}
func locationManager(manager: CLLocationManager, didFailWithError error: NSError)
{
print("Error code: " + error.localizedDescription)
}
override func viewDidLoad() {
super.viewDidLoad()
self.locationManager.delegate = self
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.startUpdatingLocation()
self.placesMap.showsUserLocation = true
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
但是,当我从弹出窗口(如下图所示)向“关于”页面启动模式搜索时,应用程序崩溃:
我查看了终端机给我的错误,这是
致命错误:解开Optional值时意外发现nil
Xcode将我指向viewDidLoad函数中的这一行:
self.placesMap.showsUserLocation = true
当我从代码中删除该特定行时,位置功能不再起作用,这是显而易见的。我已经检查了MKMapView的出口,这似乎是正确的。
我真的不知道如何避免此错误,或者确定是什么原因导致的,因此不胜感激。
最佳答案
基本上,是使placesMap
解除分配,然后调用viewDidLoad
的原因。您可以尝试将placesMap
设置为可选,而不是强行解包,因此将!
更改为属性上的?
,然后将可选链接链接到placesMap的调用位置,使self.placesMap.showsUserLocation
变为self.placesMap?.showsUserLocation
, self.placesMap.setRegion(region, animated: true)
变为self.placesMap?.setRegion(region, animated: true)