当应用程序处于后台或被杀死时如何定期获取新位置

Question

当我的应用程序处于后台或被终止时，我希望每 1 分钟获取一次新位置。 这是我的代码：

定位服务：

class LocationService: NSObject, CLLocationManagerDelegate {

    static let shared = LocationService()
    var locationManager = CLLocationManager()
    var significatLocationManager = CLLocationManager()
    var currentLocation: CLLocation!
    var timer = Timer()
    var bgTask = UIBackgroundTaskInvalid

    func startUpdatingLocation() {
        locationManager.requestAlwaysAuthorization()
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.distanceFilter = kCLDistanceFilterNone
        if #available(iOS 9.0, *) {
            locationManager.allowsBackgroundLocationUpdates = true
        }
        locationManager.delegate = self
        locationManager.startUpdatingLocation()
    }

    func stopUpdatingLocation() {
        locationManager.stopUpdatingLocation()
        timer.invalidate()
    }

    func restartUpdatingLocation() {
        locationManager.stopMonitoringSignificantLocationChanges()
        timer.invalidate()
        startUpdatingLocation()
    }

    func startMonitoringLocation() {
        locationManager.stopUpdatingLocation()
        locationManager.startMonitoringSignificantLocationChanges()
        timer.invalidate()
    }

    func changeLocationAccuracy(){
        switch locationManager.desiredAccuracy {
        case kCLLocationAccuracyBest:
            locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers
            locationManager.distanceFilter = 99999
        case kCLLocationAccuracyThreeKilometers:
            locationManager.desiredAccuracy = kCLLocationAccuracyBest
            locationManager.distanceFilter = kCLDistanceFilterNone
        default: break
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        bgTask = UIApplication.shared.beginBackgroundTask(expirationHandler: {
            UIApplication.shared.endBackgroundTask(self.bgTask)
            self.bgTask = UIBackgroundTaskInvalid
        })

        currentLocation = locations.last!

        let interval = currentLocation.timestamp.timeIntervalSinceNow
        let accuracy = self.locationManager.desiredAccuracy

        if abs(interval) < 60 && accuracy != kCLLocationAccuracyThreeKilometers {        
            timer = Timer.scheduledTimer(timeInterval: 60, target: self, selector: #selector(LocationService.changeLocationAccuracy), userInfo: nil, repeats: false)
            changeLocationAccuracy()
        }
    } 
}

应用委托：

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
     if launchOptions?[UIApplicationLaunchOptionsKey.location] != nil {
          LocationService.shared.restartUpdatingLocation()
     }
}

func applicationDidEnterBackground(_ application: UIApplication) {
     LocationService.shared.restartUpdatingLocation()
}

func applicationWillTerminate(_ application: UIApplication) {
     LocationService.shared.startMonitoringLocation()
}

视图控制器：

override func viewDidLoad() {
    LocationService.shared.startUpdatingLocation()
}

但是我的代码不起作用，当我的应用程序在后台运行几分钟后，我没有得到新的位置。当我的应用程序被暂停或终止时也是如此。 有什么解决办法吗？请不要说我使用的是 Swift 3 和 xcode 8.1。

提前致谢

Answer 1

• 如果您在应用程序已经在后台运行时调用startUpdatingLocation，那么您只会在几分钟内收到位置更新。

• 如果您在应用程序处于前台时调用 startUpdatingLocation，然后您的应用程序移至后台，您将继续无限期地接收位置更新。

• 如果您在前台调用startMonitoringSignificantLocationChanges并使其保持启用状态，那么您可以在后台调用startUpdatingLocation 并无限期地接收更新。

• 如果用户终止了您的应用程序（通过在应用程序切换器中向上滑动），那么在用户重新启动您的应用程序之前，您将不会再收到位置更新。

由于您的代码在移动到仅获取位置更新几分钟的后台时会停止并开始位置监控。如果您在应用程序移动到后台时启动位置监控前台并且什么都不做，那么您将继续接收位置更新。