Question

我正在制作一款使用地图的iPhone应用程序。我让应用程序通过故事板工作，但我决定转而以编程方式编写应用程序，这样我才能真正感觉到我正在学习我正在编写的代码。但是，我现在无法运行我的应用程序，我错误地发现了“致命错误：在解开可选值时意外发现了nil”。

我的ViewController看起来像这样：

import Foundation
import UIKit
import MapKit

class GoOut: UIViewController {
@IBOutlet var mapView: MKMapView!
let regionRadius: CLLocationDistance = 1000
let APP_ID = "5738E396-74BB-E1BD-FF13-C6916832AA00"
let SECRET_KEY = "BA71250D-582B-0E65-FF9A-35CAD17AF800"
let VERSION_NUM = "v1"

var pin_array: [[Double]] = []

var backendless = Backendless.sharedInstance()
var pressed = false
var date: NSDate? = nil

override func viewDidLoad() {
    super.viewDidLoad()
    let longPressRecogniser = UILongPressGestureRecognizer(target: self, action: "handleLongPress:")

    longPressRecogniser.minimumPressDuration = 0.5
    mapView.addGestureRecognizer(longPressRecogniser)

    mapView.delegate = self

    let initialLocation = CLLocation(latitude: 42.447918, longitude: -76.487844)

    centerMapOnLocation(initialLocation)
    backendless.initApp(APP_ID, secret:SECRET_KEY, version:VERSION_NUM)
    backendless.hostURL = "http://api.backendless.com"

    getMapPins()
    var pin_number = 0

    for element in pin_array {
        let pin = Pin(title: String(pin_number),
            coordinate:CLLocationCoordinate2D(latitude: element[0], longitude: element[1]))

        mapView.addAnnotation(pin)
        pin_number++

    }
}

我有这个类的ViewController扩展，看起来像：

import Foundation
import MapKit

extension GoOut: MKMapViewDelegate {

func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
    if let annotation = annotation as? Pin {
        let identifier = "pin"
        var view: MKPinAnnotationView
        if let dequeuedView = mapView.dequeueReusableAnnotationViewWithIdentifier(identifier)
            as? MKPinAnnotationView { // 2
                dequeuedView.annotation = annotation
                view = dequeuedView
        } else {
            view = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier)
            view.canShowCallout = false
            view.animatesDrop = true
        }
        return view
    }
    return nil
}
}

当我尝试在视图控制器中修改mapView时，我的错误就出现了。有没有人有任何建议？

编辑：我添加了

mapView = MKMapView()

到我的视图控制器，它允许应用程序运行，但没有显示地图。

不确定如何实例化MapView iOS Swift

0 个答案: