Question

我有一个实现CLLocationManagerDelegate的视图控制器。我创建了一个CLLocationManager变量：

let locationManager = CLLocationManager()

然后在viewDidLoad中，我设置了属性：

// Set location manager properties
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters
locationManager.distanceFilter = 50

问题是，即使在我检查授权状态之前，函数也会被调用。

func locationManager(manager: CLLocationManager!, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
    if (status == .AuthorizedWhenInUse) {
        // User has granted autorization to location, get location
        locationManager.startUpdatingLocation()
    }
}

任何人都可以告诉我可能导致这种情况发生的原因吗？

Answer 1

- locationManager:didChangeAuthorizationStatus:初始化后不久就会调用<{CLLocationManager。

如果您愿意，可以在委托方法中请求授权：

func locationManager(manager: CLLocationManager!, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
    switch status {
    case .NotDetermined:
        locationManager.requestAlwaysAuthorization()
        break
    case .AuthorizedWhenInUse:
        locationManager.startUpdatingLocation()
        break
    case .AuthorizedAlways:
        locationManager.startUpdatingLocation()
        break
    case .Restricted:
        // restricted by e.g. parental controls. User can't enable Location Services
        break
    case .Denied:
        // user denied your app access to Location Services, but can grant access from Settings.app
        break
    default:
        break
    }
}

请注意，您需要及时分配代表。如果你想让它发挥作用的话。

如果您以某种方式延迟委托作业，例如通过异步设置，您可能会错过对- locationManager:didChangeAuthorizationStatus:的初始调用。

Answer 2

Swift 3

func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        switch status {
        case .notDetermined:
            manager.requestAlwaysAuthorization()
            break
        case .authorizedWhenInUse:
            manager.startUpdatingLocation()
            break
        case .authorizedAlways:
            manager.startUpdatingLocation()
            break
        case .restricted:
            // restricted by e.g. parental controls. User can't enable Location Services
            break
        case .denied:
            // user denied your app access to Location Services, but can grant access from Settings.app
            break
        }
    }

Answer 3

其他答案可能会引入新的不良行为。

您可以只添加一个布尔值和一个警卫以防止首次呼叫，并附上一些解释错误的注释：

var firstTimeCalled = true

// ...    

func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {

    guard !firstTimeCalled else {
        firstTimeCalled = false
        return
    }

    // ... send status to listeners
}

Swift LocationManager didChangeAuthorizationStatus始终被调用

3 个答案: