Question

我正在使用CLLocationManager didupdatelocations，如下所示：

func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!) {
    location = locations.last as? CLLocation

    NSNotificationCenter.defaultCenter().postNotificationName("location", object: self)

}

这一切都运行正常，但我只想在距离原始位置一定距离的位置发布通知。我可以使用

吗？

locations.first

并将其与locations.last进行比较，看起来只有在用户继续在城市中移动时才会更新原始文件。

Answer 1

要计算距离，您需要两个CLLocation（比方说，newLocation和oldLocation）。您可以使用以下方法计算这两个位置之间的距离：

let distance = Double(newLocation.distanceFromLocation(oldLocation))

之后只需添加逻辑来决定何时发布通知：

if distance > myMinimum distance{
    NSNotificationCenter.defaultCenter().postNotificationName("location", object: self)
}

注意，这是计算到点（直线）之间的最短距离，它不计算路线距离。

如果你想计算两点之间的路线距离，你需要使用MKDirectionsRequest，这将通过一步一步的指示返回从A点到B点的一条或多条路线：

class func caculateDistance(){
    var directionRequest = MKDirectionsRequest()
    var sourceCoord = CLLocationCoordinate2D(latitude: -36.7346287, longitude: 174.6991812)
    var destinationCoord = CLLocationCoordinate2D(latitude: -36.850587, longitude: 174.7391745)
    var mkPlacemarkOrigen = MKPlacemark(coordinate: sourceCoord, addressDictionary: nil)
    var mkPlacemarkDestination = MKPlacemark(coordinate: destinationCoord, addressDictionary: nil)
    var source:MKMapItem = MKMapItem(placemark: mkPlacemarkOrigen)
    var destination:MKMapItem = MKMapItem(placemark: mkPlacemarkDestination)
    directionRequest.setSource(source)
    directionRequest.setDestination(destination)
    var directions = MKDirections(request: directionRequest)
    directions.calculateDirectionsWithCompletionHandler {
        (response, error) -> Void in
        if error != nil { println("Error calculating direction - \(error.localizedDescription)") }
        else {
            for route in response.routes{
                println("Distance = \(route.distance)")
                for step in route.steps!{
                    println(step.instructions)
                }  
            }
        }
    }
}

此示例代码将返回此信息：

Disntance
Distance = 16800.0

Step by Step instructions
Start on the route
At the end of the road, turn left onto Bush Road
Turn right onto Albany Expressway
At the roundabout, take the first exit onto Greville Road toward 1, Auckland
At the roundabout, take the third exit to merge onto 1 toward Auckland
Keep left
Take exit 423 onto Shelly Beach Road
Continue onto Shelly Beach Road
At the end of the road, turn right onto Jervois Road
Turn left onto Islington Street
Keep right on Islington Street
Arrive at the destination

可以轻松修改该功能以接收两个位置并返回距离和任何其他所需信息。

我希望能帮到你！

CLLocation Manager如何在一定距离后更新

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