如何停止applicationDidEnterBackground中的ViewController的locationManagerUpdates

Question

我需要在applicationDidEnterBackground時從AppDelegate停止locationUpdates，從ViewController到applicationDidBecomeActive時需要startUpdatingLocation，這是我的代碼。

如果我的locationManager在ViewController中，該怎么辦。

import CoreLocation

class ViewController: UIViewController, CLLocationManagerDelegate

var seenError : Bool = false
var locationFixAchieved : Bool = false
var locationStatus : NSString = "Not Started"

var locationManager: CLLocationManager!

override func viewDidLoad() {
    super.viewDidLoad()
}

  func initLocationManager() {
   seenError = false
   locationFixAchieved = false
    locationManager = CLLocationManager()
   locationManager.delegate = self
   locationManager.locationServicesEnabled
   locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.requestAlwaysAuthorization()
}

  func locationManager(manager: CLLocationManager!, didFailWithError error: NSError!) {
    locationManager.stopUpdatingLocation()
    if (error) {
        if (seenError == false) {
            seenError = true
           print(error)
        }
    }
}

func locationManager(manager: CLLocationManager!, didUpdateLocations locations: AnyObject[]!) {
    if (locationFixAchieved == false) {
        locationFixAchieved = true
        var locationArray = locations as NSArray
        var locationObj = locationArray.lastObject as CLLocation
        var coord = locationObj.coordinate

        println(coord.latitude)
        println(coord.longitude)
    }
}

 func locationManager(manager: CLLocationManager!,
    didChangeAuthorizationStatus status: CLAuthorizationStatus) {
        var shouldIAllow = false

        switch status {
        case CLAuthorizationStatus.Restricted:
            locationStatus = "Restricted Access to location"
        case CLAuthorizationStatus.Denied:
            locationStatus = "User denied access to location"
        case CLAuthorizationStatus.NotDetermined:
            locationStatus = "Status not determined"
        default:
            locationStatus = "Allowed to location Access"
            shouldIAllow = true
        }
        NSNotificationCenter.defaultCenter().postNotificationName("LabelHasbeenUpdated", object: nil)
        if (shouldIAllow == true) {
            NSLog("Location to Allowed")
            // Start location services
            locationManager.startUpdatingLocation()
        } else {
            NSLog("Denied access: \(locationStatus)")
        }
}

Answer 1

NSNotificationCenter是在應用程序內發送消息的簡單方法。 每個需要響應此類消息的類都注冊了一個觀察者以偵聽該消息。

AppDelegate中：

func applicationDidEnterBackground(application: UIApplication) {
    // Send a message that informs all listening classes for entering background
    NSNotificationCenter.defaultCenter().postNotification(NSNotification(name: "appEntersBackground", object: nil))
}

func applicationDidBecomeActive(application: UIApplication) {
    // Send a message that informs all listening classes for becoming active again
    NSNotificationCenter.defaultCenter().postNotification(NSNotification(name: "appBecomesActive", object: nil))
}

斯威夫特4.2

NotificationCenter.default.post(name: Notification.Name("appEntersBackground"), object: nil)

視圖控制器

在您的viewController中，注冊消息的觀察者：

class ViewController: UIViewController, CLLocationManagerDelegate {
    ...

    override func viewDidLoad() {
        super.viewDidLoad()

        // register observers
        NSNotificationCenter.defaultCenter().addObserver(self, selector: "enterBackground", name: "appEntersBackground", object: nil)
        NSNotificationCenter.defaultCenter().addObserver(self, selector: "becomeActive", name: "appBecomesActive", object: nil)
    }

    deinit {
        // remove observers
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }

    // app enters background
    func enterBackground() {
        self.locationManager.stopUpdatingLocation()
    }

    // app becomes active
    func becomeActive() {
        self.locationManager.startUpdatingLocation()
    }

}

斯威夫特4.2

    NotificationCenter.default.addObserver(self, selector: #selector(enterBackground), name: Notification.Name("appEntersBackground"), object: nil)

@objc func enterBackground() {
            self.locationManager.stopUpdatingLocation()
        }

請注意，除非您已在Info.plist為后台任務注冊了應用程序，否則locationmanager會停止在后台更新位置。

Answer 2

您可以觸發通知startUpdatingLocation從applicationDidBecomeActive和stopUpdatingLocation從applicationDidEnterBackground 。 然后，您可以在視圖控制器中偵聽這些通知以管理locationManager 。

Answer 3

您可以使用此代碼-

func applicationDidEnterBackground(application: UIApplication) {

    self.locationManager.stopUpdatingLocation() 
}

func applicationDidBecomeActive(application: UIApplication) {

    self.locationManager.startUpdatingLocation()
}

還有一個建議，您可以在initLocationManager方法中進行檢查-

if (self.locationManager.respondsToSelector(Selector("requestAlwaysAuthorization"))) {
        self.locationManager.requestAlwaysAuthorization()
    }