swift - 使用 slider SWIFT4 调整 MKCircle 的大小

Question

我的目的是做与 Facebook 应用程序完全相同的事情。这是我当前的代码:

class MapFilterViewController: UIViewController, CLLocationManagerDelegate {

    @IBOutlet weak var mapView: MKMapView!
    @IBOutlet weak var distanceSlider: UISlider!
    @IBOutlet weak var distanceLabel: UILabel!
    @IBOutlet weak var applyButton: UIButton!

    let locationManager = CLLocationManager()


    override func viewDidLoad() {
        super.viewDidLoad()

        applyButton.layer.cornerRadius = 5

        locationManager.delegate = self
        locationManager.requestWhenInUseAuthorization()
        locationManager.startUpdatingLocation()

        mapView.delegate = self

    }

    func showCircle(coordinate: CLLocationCoordinate2D, radius: CLLocationDistance, mapView: MKMapView) {
        let circle = MKCircle(center: coordinate, radius: radius)
        mapView.add(circle)
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

        let location = locations.last as! CLLocation

        let center =  CLLocationCoordinate2DMake(location.coordinate.latitude, location.coordinate.longitude)
        let span = MKCoordinateSpanMake(0.05, 0.05)
        let region = MKCoordinateRegion(center : center, span : span)

        print("longitude = \(location.coordinate.longitude), latitude = \(location.coordinate.latitude)")


        mapView.setRegion(region, animated: true)
        mapView.showsUserLocation = true

        showCircle(coordinate: location.coordinate, radius: 1000, mapView: mapView)
        print(location.coordinate)

    }
    @IBAction func sliderValueChange(_ sender: Any) {
        distanceLabel.text = String(distanceSlider.value) + " km"


    }    

我不明白如何在 sliderValueChange 操作中获取圆的半径并获得相同的动画

已经搜索了很多，大部分结果都是 Objective-C 的，我现在已经学习 Swift 3 周了。

感谢您的帮助

Answer 1

我认为最简单的方法是删除圆圈并创建一个新圆圈(因为您无法修改圆圈的半径)。

这里是一些您可以使用的代码:

var circle: MKCircle?

@IBAction func sliderValueChange(_ sender: UISlider) {
    mapView.remove(circle)
    let newRadius = sender.value * 1000
    circle = MKCircle(center: coordinate, radius: radius)
    mapView.add(circle)
}

当你学习时，我认为你应该从类似的事情开始。您也可以尝试调整叠加层的比例，但我认为这会更复杂一些，而且我不确定结果会好得多。