ios - Swift:当应用程序在后台时调用 .requestLocation()

Question

如果我在应用程序后台调用 .requestLocation()，则永远不会调用 locationManager didUpateLocations 方法。当应用程序打开时它会起作用。我已设置 .allowsBackgroundLocationUpdates = true 并且测试手机选择 .authorizedAlways 作为授权状态。 requestLocation 不能在后台工作吗？

为了澄清，我在 didReceiveRemoteNotification 委托(delegate)方法中调用它。每次我向设备发送远程推送通知时，如果应用程序在后台，我希望调用 .requestLocation() 。这不可能吗？

didReceiveRemoteNotification:

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

    if CLLocationManager.authorizationStatus() == .authorizedAlways {
        locationManager.requestLocation()
    }

    completionHandler(UIBackgroundFetchResult.newData)
}

Answer 1

您的问题是 requestLocation 将异步完成；可能需要一些时间来确定用户的位置并调用 didUpdateLocations 委托(delegate)方法。

调用completionHandler告诉iOS您已经完成后台处理。当您在 requestLocation 之后立即执行此操作时，iOS 会在调用位置委托(delegate)之前挂起您的应用。

您可以使用 DispatchGroup 来确定何时检索到位置以及您何时准备好暂停:

class AppDelegate: UIApplicationDelegate, CLLocationManagerDelegate {
    var backgroundDispatchGroup: DispatchGroup?


    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

        if CLLocationManager.authorizationStatus() == .authorizedAlways {

            self.backgroundDispatchGroup = DispatchGroup()
            self.backgroundDispatchGroup?.enter()
            locationManager.requestLocation()

            self.backgroundDispatchGroup?.notify {
                completionHandler(UIBackgroundFetchResult.newData)
                self.backgroundDispatchGroup = nil
            }

         } else {
             completionHandler(UIBackgroundFetchResult.noData)
         }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        // Do whatever with the location

        self.backgroundDispatchGroup?.leave()
    }
}