如何从MKmapview的可见区域获取半径? [英] How to get radius from visible area of MKmapview?

问题描述

我能够获得地图视图的可见矩形，并且地图视图的中心点和跨度增量也可以通过mkmaap视图方法获得: 要变得可见，请使用:mapView.visibleMapRect.获取中心点:使用map view.centerCoordinate并获取跨度:使用mapView.region.span.

I am able to get visible rectangle of map view and also centre point of map view and span deltas are also get from mkmaap view methods: To get visible are :mapView.visibleMapRect is used . To get centre point: map view.centerCoordinate is used and to get span: mapView.region.span is used.

现在我拥有所有信息，如何使用计算来计算可见半径?谁能详细解释一下我?

Now I have all the information, how can i calculate radius of visible are using calculation? Can anyone explain me in detail?

我已经看到这个问题但答案是我的跨度不是可见区域的半径.

I have seen this question but the answer is giving me span not radius of visible area.

推荐答案

使用 Swift 3.0 ，您可以使用扩展程序简化生活:

With Swift 3.0 you can use extension to simplify your life:

extension MKMapView {

    func topCenterCoordinate() -> CLLocationCoordinate2D {
        return self.convert(CGPoint(x: self.frame.size.width / 2.0, y: 0), toCoordinateFrom: self)
    }

    func currentRadius() -> Double {
        let centerLocation = CLLocation(coordinate: self.centerCoordinate)
        let topCenterCoordinate = self.topCenterCoordinate()
        let topCenterLocation = CLLocation(coordinate: topCenterCoordinate)
        return centerLocation.distance(from: topCenterLocation)
    }

}

使用 Swift 4.0 :

extension MKMapView {

    func topCenterCoordinate() -> CLLocationCoordinate2D {
        return self.convert(CGPoint(x: self.frame.size.width / 2.0, y: 0), toCoordinateFrom: self)
    }

    func currentRadius() -> Double {
        let centerLocation = CLLocation(latitude: self.centerCoordinate.latitude, longitude: self.centerCoordinate.longitude)
        let topCenterCoordinate = self.topCenterCoordinate()
        let topCenterLocation = CLLocation(latitude: topCenterCoordinate.latitude, longitude: topCenterCoordinate.longitude)
        return centerLocation.distance(from: topCenterLocation)
    }

}

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