Question

我正在创建一个以经度，纬度，海拔和速度出现的应用。

每当我运行应用程序时： 1.标签中没有显示位置数据2.我收到此错误消息：

fatal error: unexpectedly found nil while unwrapping an Optional value

我做错了什么？谢谢！

@IBOutlet weak var longitude: UILabel!
@IBOutlet weak var latitude: UILabel!
@IBOutlet weak var altitude: UILabel!
@IBOutlet weak var speed: UILabel!

var locationManager: CLLocationManager = CLLocationManager()
var startLocation: CLLocation!

@IBAction func reset(sender: AnyObject) {
    startLocation = nil
}



func locationManager(manager: CLLocationManager!,
    didUpdateLocations locations: [AnyObject]!)
{
    var latestLocation: AnyObject = locations[locations.count - 1]

    latitude.text = String(format: "%.4f",
        latestLocation.coordinate.latitude)
    longitude.text = String(format: "%.4f",
        latestLocation.coordinate.longitude)
    altitude.text = String(format: "%.4f",
        latestLocation.altitude)


    if startLocation == nil {
        startLocation = latestLocation as! CLLocation
    }

    var distanceBetween: CLLocationDistance =
    latestLocation.distanceFromLocation(startLocation)

}

func locationManager(manager: CLLocationManager!,
    didFailWithError error: NSError!) {

}

则...

override func viewDidLoad() {
    super.viewDidLoad()


    // Location
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.delegate = self
    locationManager.requestWhenInUseAuthorization()
    locationManager.startUpdatingLocation()
    startLocation = nil


    // Do any additional setup after loading the view, typically from a nib.

}

Answer 1

将startLocation作为一个隐式解包的可选项进行清理在这里是非常危险的，因为它并非总是如此！= nil。

尝试将其定义为可选项：

var startLocation: CLLocation?

并相应地更改代码的resto，并在需要时进行适当的检查。

例如，当您计算距离时：

if let startLocation = startLocation {
       var distanceBetween: CLLocationDistance =
       latestLocation.distanceFromLocation(startLocation)
}

也许您的代码中的其他位置startLocation可能nil

由于尝试设置纬度标签文本时会出现nil异常，因此我首先会检查是否通过Interface Builder正确连接了该标签。它的声明左边的小子弹是彩色的吗？无论如何，您可以在该行代码之前放置一个断点，而不是检查什么是零而不应该。

为什么我的CLLocation信息没有出现？

1 个答案: