使用 SwiftUI 上的当前位置更新 MapView

Question

尝试更新 Project 14 of 100daysOfSwiftUI 的地图视图以显示我当前的位置，问题我无法放大移动

我有这段代码，我将 @Binding var currentLocation : CLLocationCoordinate2D 和 view.setCenter(currentLocation, animated: true) 添加到我的 MapView 中，所以我有一个按钮可以发送该值，并且视图实际上移动到该位置的速度非常慢，但我可以再离开

import SwiftUI
import MapKit

struct MapView: UIViewRepresentable {

    @Binding var centerCoordinate: CLLocationCoordinate2D
    @Binding var selectedPlace: MKPointAnnotation?
    @Binding var showingPlaceDetails: Bool
    @Binding var currentLocation : CLLocationCoordinate2D

    var annotations: [MKPointAnnotation]

    func makeUIView(context: Context) -> MKMapView {
        let mapView = MKMapView()
        mapView.delegate = context.coordinator
        return mapView
    }

    func updateUIView(_ view: MKMapView, context: Context) {

        if annotations.count != view.annotations.count {
            view.removeAnnotations(view.annotations)
            view.addAnnotations(annotations)
        }

        view.setCenter(currentLocation, animated: true)

    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

 class Coordinator: NSObject, MKMapViewDelegate{

    var parent: MapView
    init(_ parent: MapView) {
        self.parent = parent
    }

    func mapViewDidChangeVisibleRegion(_ mapView: MKMapView) {
         parent.centerCoordinate = mapView.centerCoordinate
     }

     func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
         let identifier = "PlaceMark"
         var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: identifier)
         if annotationView == nil {
             annotationView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: identifier)
             annotationView?.canShowCallout = true
             annotationView?.rightCalloutAccessoryView = UIButton(type: .detailDisclosure)

         } else {
             annotationView?.annotation = annotation
         }

         return annotationView
     }

     func mapView(_ mapView: MKMapView, annotationView view: MKAnnotationView, calloutAccessoryControlTapped control: UIControl) {
         guard let placemark = view.annotation as? MKPointAnnotation else {return}
         parent.selectedPlace = placemark
         parent.showingPlaceDetails = true

     }

    }
}

这是我的 swiftUI 视图

...
    @State private var currentLocation = CLLocationCoordinate2D()

    var body: some View {
        ZStack{

            MapView(centerCoordinate: $centerCoordinate, selectedPlace: $selectedPlace, showingPlaceDetails: $showingPlaceDetails, currentLocation: $currentLocation ,  annotations: locations)
           // MapView(centerCoordinate: $centerCoordinate, selectedPlace: $selectedPlace, showingPlaceDetails: $showingPlaceDetails, annotations: locations)
                .edgesIgnoringSafeArea(.all)
            VStack{
                Spacer()
                HStack{
                    Spacer()
                    Button(action: {
                        self.getCurrentLocation()
                    }){
                        ButtonIcon(icon: "location.fill")
                    }
                }
                .padding()
            }
        }
        .onAppear(perform: getCurrentLocation)
    }

    func getCurrentLocation() {

        let lat = locationManager.lastLocation?.coordinate.latitude ?? 0
        let log = locationManager.lastLocation?.coordinate.longitude ?? 0

        self.currentLocation.latitude = lat
        self.currentLocation.longitude = log

    }
    ...

更新

感谢支持我使用这个课程拨打locationManager.requestWhenInUseAuthorization()

import Foundation
import CoreLocation
import Combine

class LocationManager: NSObject, ObservableObject {

    override init() {
        super.init()
        self.locationManager.delegate = self
        self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
        self.locationManager.requestWhenInUseAuthorization()
        self.locationManager.startUpdatingLocation()
    }

    @Published var locationStatus: CLAuthorizationStatus? {
        willSet {
            objectWillChange.send()
        }
    }

    @Published var lastLocation: CLLocation? {
        willSet {
            objectWillChange.send()
        }
    }

    var statusString: String {
        guard let status = locationStatus else {
            return "unknown"
        }

        switch status {
        case .notDetermined: return "notDetermined"
        case .authorizedWhenInUse: return "authorizedWhenInUse"
        case .authorizedAlways: return "authorizedAlways"
        case .restricted: return "restricted"
        case .denied: return "denied"
        default: return "unknown"
        }

    }

    let objectWillChange = PassthroughSubject<Void, Never>()

    private let locationManager = CLLocationManager()
}

extension LocationManager: CLLocationManagerDelegate {

    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        self.locationStatus = status
        print(#function, statusString)
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        guard let location = locations.last else { return }
        self.lastLocation = location
        print(#function, location)
    }

}

当我按下按钮时，我只想将我的地图视图集中在我当前的位置上

Answer 1

你从来没有在哪里打电话给locationManager.requestWhenInUseAuthorization()。当我这样做时（当然，确保Info.plist 有一个NSLocationWhenInUseUsageDescription 的条目），它正确地更新了位置。

例如

func getCurrentLocation() {
    if CLLocationManager.authorizationStatus() == .notDetermined {
        locationManager.requestWhenInUseAuthorization()
    }
    if let coordinate = locationManager.location?.coordinate {
        currentLocation = coordinate
    }
}

现在，这只是一个快速而肮脏的修复，以证明它有效。但这不太对，因为第一次调用getCurrentLocation时，如果它必须向用户请求许可，它是异步执行的，这意味着当你到达lastLocation时它还没有位置在您的实施中行。这是一次性的事情，但仍然不能接受。如果需要，你会想要你的 CLLocationManagerDelegate 更新 currentLocation。但希望您在这里有足够的信息来诊断为什么CLLocationManager 没有正确捕获您的位置。

---

FWIW，您可以考虑使用 .follow 中的 userTrackingMode，这样就不需要所有手动位置管理器和 currentLocation 的东西。我要提到的一个警告（因为我有一天花了几个小时试图诊断这种奇怪的行为），如果你用以下方式初始化地图视图，userTrackingMode 将不起作用：

let mapView = MKMapView()

但如果你给它一些框架，它就会起作用，例如：

let mapView = MKMapView(frame: UIScreen.main.bounds)

---

所以，对于用户跟踪模式：

struct MapView: UIViewRepresentable {
    @Binding var userTrackingMode: MKUserTrackingMode

    func makeUIView(context: Context) -> MKMapView {
        let mapView = MKMapView(frame: UIScreen.main.bounds)
        mapView.delegate = context.coordinator
        mapView.userTrackingMode = userTrackingMode

        return mapView
    }

    func updateUIView(_ view: MKMapView, context: Context) {
        view.userTrackingMode = userTrackingMode
    }

    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }

    class Coordinator: NSObject, MKMapViewDelegate {
        var parent: MapView

        init(_ parent: MapView) {
            self.parent = parent
        }

        // MARK: - MKMapViewDelegate

        func mapView(_ mapView: MKMapView, didChange mode: MKUserTrackingMode, animated: Bool) {
            DispatchQueue.main.async {
                self.parent.$userTrackingMode.wrappedValue = mode
            }
        }

        // note, implementation of `mapView(_:viewFor:)` is generally not needed if we register annotation view class
    }
}

然后，我们可以在关闭用户跟踪时出现一个“关注”按钮（这样您就可以重新打开它）：

struct ContentView: View {
    @State var userTrackingMode: MKUserTrackingMode = .follow

    private var locationManager = CLLocationManager()

    var body: some View {
        ZStack {
            MapView(userTrackingMode: $userTrackingMode)
                .edgesIgnoringSafeArea(.all)

            VStack {
                HStack {
                    Spacer()

                    if self.userTrackingMode == .none {
                        Button(action: {
                            self.userTrackingMode = .follow
                        }) {
                            Text("Follow")
                        }.padding()
                    }
                }

                Spacer()
            }
        }.onAppear { self.requestAuthorization() }
    }

    func requestAuthorization() {
        if CLLocationManager.authorizationStatus() == .notDetermined {
            locationManager.requestWhenInUseAuthorization()
        }
    }
}