Swift MapView卡在用户当前位置

Question

当前，我的代码在用户的当前位置上删除了PIN。当我尝试将地图移动时，有一个小问题，因为视图将向后移动并以当前位置引脚为中心。我希望用户能够浏览地图并将其移动，如果用户切换视图控制器（转到另一个选项卡）然后返回，则该地图将围绕用户位置引脚。我一直在尝试修改此代码来执行此操作，但是我从哪里开始运气。

import UIKit
import MapKit
import CoreLocation
let newPin = MKPointAnnotation()
class MapVC: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate {

@IBOutlet weak var map: MKMapView!
 let locationManager =  CLLocationManager()
override func viewDidLoad() {
    super.viewDidLoad()
    // User's location
    locationManager.delegate = self
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    if #available(iOS 8.0, *) {
    locationManager.requestAlwaysAuthorization()
    } else {
    // Fallback on earlier versions
    }
    locationManager.startUpdatingLocation()

    // add gesture recognizer
    let longPress = UILongPressGestureRecognizer(target: self, action: #selector(MapVC.mapLongPress(_:))) // colon needs to pass through info
    longPress.minimumPressDuration = 1.5 // in seconds
    //add gesture recognition
    map.addGestureRecognizer(longPress)
}
// func called when gesture recognizer detects a long press
func mapLongPress(_ recognizer: UIGestureRecognizer) {
    print("A long press has been detected.")
    let touchedAt = recognizer.location(in: self.map) // adds the location on the view it was pressed
    let touchedAtCoordinate : CLLocationCoordinate2D = map.convert(touchedAt, toCoordinateFrom: self.map) // will get coordinates
    let newPin = MKPointAnnotation()
    newPin.coordinate = touchedAtCoordinate
    map.addAnnotation(newPin)

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

    map.removeAnnotation(newPin)
    let location = locations.last! as CLLocation
    let center = CLLocationCoordinate2D(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)
    let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))
    //set region on the map
    map.setRegion(region, animated: true)
    newPin.coordinate = location.coordinate
    map.addAnnotation(newPin)


}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

Answer 1

您的代码有几个问题：

您在全局范围内声明一个变量newPin，在mapLongPress(...)中，您在本地声明新变量let newPin = ...，因此未使用全局newPin。

在didUpdateLocations()中，您首先删除（全局）newPin注释（为什么??），然后在功能末尾再次设置它。因为全局newPin永远不会设置为有用的任何东西，这永远不会得到所需的结果。

此外，在didUpdateLocations()中，您将地图的区域设置为当前位置。这是在每个位置更新上完成的，在尝试铺平地图时给出了奇怪的结果。

出现视图时设置中心和区域，请尝试类似的东西：

class MapVC: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate {
    @IBOutlet weak var map: MKMapView!
    let locationManager =  CLLocationManager()
    // class variable for the current location
    var lastLocation: CLLocation?
    override func viewDidLoad() {
        // ...
    }
    override func viewDidAppear(_ animated: Bool) {
        if self.lastLocation != nil {
            // set center and region to current location
            let center = CLLocationCoordinate2D(latitude: self.lastLocation.coordinate.latitude, longitude: self.lastLocation.coordinate.longitude)
            let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))
            //set region on the map
            map.setRegion(region, animated: true)
        }
    }
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        self.lastLocation = locations.last
    }
}