Question

我为CoreLocation的位置管理器实现了一个单例对象，我正在使用Swift 1.2及更高版本的类常量方法开发的应用程序here。

虽然当我尝试直接或使用getter方法访问currentLocation变量时，我得到nil。

我错过了什么？

实施

import Foundation
import CoreLocation

class LocationService: NSObject, CLLocationManagerDelegate {
  static let sharedInstance = LocationService()

  var locationManager: CLLocationManager!
  var currentLocation: CLLocationCoordinate2D!
  var currentDirection: StepDirection!

  private override init() {
    super.init()

    locationManager = CLLocationManager()

    locationManager.requestAlwaysAuthorization()

    locationManager.delegate = self

    locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
    locationManager.headingFilter = kCLHeadingFilterNone
    locationManager.distanceFilter = 1
  }

  // MARK: Control Methods
  func startUpdatingLocation() {
    locationManager.startUpdatingLocation()
    print("Location updates are started.")
  }

  func stopUpdatingLocation() {
    locationManager.stopUpdatingLocation()
    print("Location updates are stopped.")
  }

  func startUpdatingHeading() {
    locationManager.startUpdatingHeading()
    print("Compass updates are started.")
  }

  func stopUpdatingHeading() {
    locationManager.stopUpdatingHeading()
    print("Compass updates are stopped.")
  }

  // MARK: CoreLocation Location Updates
  func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    // If location data can be determined
    if let location = locations.last! as CLLocation! {
      currentLocation = location.coordinate
//      print("Current Location: \(currentLocation)")
      NSNotificationCenter.defaultCenter().postNotificationName("LocationUpdate", object: self,
                                                                userInfo: ["longitude": currentLocation.longitude,
                                                                  "latitude": currentLocation.latitude])
    }
  }

  func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
    print("Location Manager: \(error)")

    NSNotificationCenter.defaultCenter().postNotificationName("LocationUpdateError", object: self,
                                                              userInfo: nil)
  }

  // MARK: CoreLocation Heading Updates
  func locationManager(manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
    let trueHeading = newHeading.trueHeading

    var declanation = (newHeading.trueHeading - newHeading.magneticHeading)
    declanation = 50.0

    if (0.0+declanation <= trueHeading) && (trueHeading <= 90.0+declanation) {
      currentDirection = StepDirection.Right
    } else if (90.0+declanation < trueHeading) && (trueHeading <= 180.0+declanation) {
      currentDirection = StepDirection.Down
    } else if (180.0+declanation < trueHeading) && (trueHeading <= 270.0+declanation) {
      currentDirection = StepDirection.Left
    } else if (270.0+declanation < trueHeading) && (trueHeading <= 360.0+declanation) {
      currentDirection = StepDirection.Up
    }

    NSNotificationCenter.defaultCenter().postNotificationName("CompassUpdate", object: self, userInfo: ["currentDirection": currentDirection.rawValue])
  }

  func locationManagerShouldDisplayHeadingCalibration(manager: CLLocationManager) -> Bool {
    return true
  }

  // MARK: Access Methods
  func getCurrentLocation() -> CLLocationCoordinate2D! {
    return currentLocation
  }
}

使用

我首先尝试访问它，如下所示：

LocationService.sharedInstance.currentLocation或LocationService.sharedInstance.getCurrentLocation

然后我将共享实例分配给变量，认为我没有保留状态：

locationService = LocationService.sharedInstance

然后使用访问方法或变量名称：

locationService.currentLocation或locationService.getCurrentLocation

Answer 1

您需要调用startUpdating函数以让位置管理器开始更新位置。

private override init() {
super.init()

locationManager = CLLocationManager()

locationManager.requestAlwaysAuthorization()

locationManager.delegate = self

locationManager.desiredAccuracy = kCLLocationAccuracyBestForNavigation
locationManager.headingFilter = kCLHeadingFilterNone
locationManager.distanceFilter = 1
locationManager.startUpdatingLocation()
}

正如您在评论中所说，位置管理员将不断尝试获取用户的位置，直到调用停止更新为止。

讨论此方法立即返回。调用此方法会导致位置管理器获取初始位置修复（可能需要几秒钟），并通过调用其locationManager：didUpdateLocations：方法来通知您的委托。之后，接收器主要在超出distanceFilter属性值时生成更新事件。但是，更新可能会在其他情况下提供。例如，如果硬件收集更准确的位置读数，接收器可以发送另一个通知。

您可以在此处阅读更多内容：https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLLocationManager_Class/#//apple_ref/occ/instm/CLLocationManager/startUpdatingLocation

您可以使用位置管理器的位置属性（您已在委托方法中执行）从委托方法访问新的位置数据。

无法读取单例对象的变量

1 个答案: