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[英]How to work with Page control using NSTimer for automatic scrolling in swift4
[英]How to make segment control work in Swift4?
我創建了這樣的自定義視圖:
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
}
}
沒有構建問題。 但是當我運行應用程序並點擊分段控件上的任何按鈕時,它會中止該應用程序。 無法弄清問題是什么。 我正在使用Xcode 9 beta。
我想你設置選擇器的方式導致問題改變它
segmentedControl.addTarget(self, action: #selector(mapTypeChanged), for: .valueChanged)
並將@IBAction添加到mapTypeChanged中
@IBAction func mapTypeChanged(segControl: UISegmentedControl) {
真正的答案是其他兩個的混合。
segmentedControl.addTarget(self, action: #selector(mapTypeChanged:), for: .valueChanged)
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