ios - 如何使段控制在 Swift4 中工作？

Question

我创建了这样的自定义 View :

import UIKit
import MapKit

class MapViewController: UIViewController {

    var mapView: MKMapView!

    func mapTypeChanged(segControl: UISegmentedControl){
        switch segControl.selectedSegmentIndex {
        case 0:
            mapView.mapType = .standard
        case 1:
            mapView.mapType = .hybrid
        case 2:
            mapView.mapType = .satellite
        default:
            break
        }

    }
    override func loadView() {
        mapView = MKMapView()

        view = mapView

        let segmentedControl = UISegmentedControl(items: ["Standard", "Hybrid", "Satellite"])

        segmentedControl.backgroundColor = UIColor.white.withAlphaComponent(0.5)

        segmentedControl.selectedSegmentIndex = 0

            segmentedControl.addTarget(self, action: "mapTypeChanged", for: .valueChanged)


        segmentedControl.translatesAutoresizingMaskIntoConstraints = false

        view.addSubview(segmentedControl)

        let topConstraint = segmentedControl.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor, constant: 8)

        let margins = view.layoutMarginsGuide

        let leadingContraint = segmentedControl.leadingAnchor.constraint(equalTo: margins.leadingAnchor)

        let trailingConstraint = segmentedControl.trailingAnchor.constraint(equalTo: margins.trailingAnchor)

        topConstraint.isActive = true
        leadingContraint.isActive = true
        trailingConstraint.isActive = true

    }

} 

没有构建问题。但是当我运行该应用程序并点击分段控件上的任何按钮时，它会中止该应用程序。无法弄清楚是什么问题。我正在使用 Xcode 9 beta。

Answer 1

我猜你设置选择器的方式导致了这个问题 改成

segmentedControl.addTarget(self, action: #selector(mapTypeChanged), for: .valueChanged)

然后将@IBAction 添加到您的mapTypeChanged 中

@IBAction func mapTypeChanged(segControl: UISegmentedControl) {