在地图上重复引脚注释

Question

我刚开始学习Swift。

问题：

当我触摸地图以放置图钉注释并拖动我的手指时，它会创建重复的注释线。

import UIKit
import MapKit
import CoreLocation
class ViewController: UIViewController, CLLocationManagerDelegate, MKMapViewDelegate {
    @IBOutlet weak var map: MKMapView!
    var manager:CLLocationManager!
    override func viewDidLoad() {
        super.viewDidLoad()
        //Manager for current location
        manager = CLLocationManager()
        manager.delegate = self
        manager.desiredAccuracy = kCLLocationAccuracyBest
        manager.requestWhenInUseAuthorization()
        manager.startUpdatingLocation()
        //Getting touch Gesture to add bookmark
        let uilpgr = UILongPressGestureRecognizer(target: self, action: "action:")
        uilpgr.minimumPressDuration = 1
        uilpgr.numberOfTouchesRequired = 1
        map.addGestureRecognizer(uilpgr)
    }
    func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        let userLocation:CLLocation = locations[0]
        let latitude:CLLocationDegrees = userLocation.coordinate.latitude
        let longitude:CLLocationDegrees = userLocation.coordinate.longitude
        let latDelta:CLLocationDegrees = 0.002
        let lonDelta:CLLocationDegrees = 0.002
        let span:MKCoordinateSpan = MKCoordinateSpanMake(latDelta, lonDelta)
        let location:CLLocationCoordinate2D = CLLocationCoordinate2DMake(latitude, longitude)
        let region:MKCoordinateRegion = MKCoordinateRegionMake(location, span)
        map.setRegion(region, animated: true)
    }
    func action(gestureRecognizer: UIGestureRecognizer) {
        let touchPoint = gestureRecognizer.locationInView(self.map)
        let newCoordinate: CLLocationCoordinate2D = map.convertPoint(touchPoint, toCoordinateFromView: self.map)
        print(newCoordinate)
        let annotation = MKPointAnnotation()
        annotation.coordinate = newCoordinate
        annotation.title = "New Place"
        annotation.subtitle = "One day I'll go here..."
        map.addAnnotation(annotation)
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

Answer 1

Xcode 8.2•Swift 3.0.2

您只需要检查手势识别器状态，并确保是否.Began返回。只需在操作方法的顶部添加if if条件：

func action(_ gestureRecognizer: UIGestureRecognizer) {

    if gestureRecognizer.state != UIGestureRecognizerState.began {
        return
    }

    //  your code

如果您想让用户在触摸时移动图钉，则需要切换手势识别器状态并在gestureRecognizer.state更改时更新注释坐标：

func action(_ gestureRecognizer: UIGestureRecognizer) {
    switch gestureRecognizer.state {
    case .began:
        let annotation = MKPointAnnotation()
        annotation.coordinate = mapView.convert(gestureRecognizer.location(in: mapView), toCoordinateFrom: mapView)
        annotation.title =  "Untitled"
        mapView.addAnnotation(annotation)
    case .changed:
        if let annotation = (mapView.annotations.filter{$0.title! == "Untitled" }).first as? MKPointAnnotation {
            annotation.coordinate =  mapView.convert(gestureRecognizer.location(in: mapView), toCoordinateFrom: mapView)
        }
    case .cancelled:
        if let annotation = (mapView.annotations.filter{$0.title! == "Untitled" }).first as? MKPointAnnotation {
            mapView.removeAnnotation(annotation)
        }
    // you can also prompt the user here for the annotation title
    case .ended:
        if let annotation = (mapView.annotations.filter{$0.title! == "Untitled" }).first as? MKPointAnnotation {
            let alert = UIAlertController(title: "New Annotation", message: "", preferredStyle: .alert)
            var inputTextField: UITextField?
            alert.addAction(UIAlertAction(title: "Add", style: .default) { _ in
                if  let annotationTitle = inputTextField?.text {
                    annotation.title =  annotationTitle
                    annotation.subtitle = "Lat:\(String(format: "%.06f", annotation.coordinate.latitude))  Lon:\(String(format: "%.06f", annotation.coordinate.longitude))"
                }
            })
            alert.addTextField(configurationHandler: { textField in
                textField.placeholder = "Place Description"
                inputTextField = textField
            })
            alert.addAction(UIAlertAction(title: "Cancel", style: .cancel){ _ in
                self.mapView.removeAnnotation(annotation)
            })
            present(alert, animated: true, completion: nil)
        }
    default:
        print("default")
    }
}