设置ObservableObject时不显示地图

Question

返回视图之前，尝试将用户的当前位置存储在ObservableObject类变量中。

struct MapWithLocation: View {
    @ObservedObject var event = Event()
    @ObservedObject var locationManager = LocationManager()

    var body: some View {

        let coordinate = self.locationManager.location != nil ? self.locationManager.location!.coordinate : CLLocationCoordinate2D()

        //Store this location
        event.latitude = coordinate.latitude
        event.longitude = coordinate.longitude

        return ZStack {
            MapView()
            Text("\(coordinate.latitude), \(coordinate.longitude)")
        }
    }
}

import SwiftUI
import MapKit

struct MapView: UIViewRepresentable {

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

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

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

    }

}

只要我注释掉设置event.latitude和event.longitude（定义为CLLocationDegrees）的两行，该方法就可以很好地工作。但是，当我取消注释这些行时，“文本”视图将显示正确的坐标，并带有空白地图，如下图所示。知道发生了什么事吗？

Answer 1

编辑：这是一种将用户当前位置存储在ObservableObject类变量中的方法。 （请注意，您还需要修改Info.plist）

import Foundation
import SwiftUI
import MapKit

class Event: ObservableObject {
  @Published var latitude: Double = 0.0
  @Published var longitude: Double = 0.0
}

class LocationManager {
var locationManager = CLLocationManager()

func getUserLocation(into event: Event) {
    let status = CLLocationManager.authorizationStatus()
    self.locationManager.requestAlwaysAuthorization()
    self.locationManager.requestWhenInUseAuthorization()
    if status == .authorizedAlways || status == .authorizedWhenInUse {
        if CLLocationManager.locationServicesEnabled() {
            self.locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
            self.locationManager.startUpdatingLocation()
            DispatchQueue.main.asyncAfter(deadline: .now() + 1.0, execute: {
                if let theLocation = self.locationManager.location {
                    event.latitude = theLocation.coordinate.latitude
                    event.longitude = theLocation.coordinate.longitude
                }
            })
        }
    }
}
}

struct ContentView: View {
@ObservedObject var event = Event()
var locationManager = LocationManager()
var body: some View {
    ZStack {
        MapView().edgesIgnoringSafeArea(.vertical)
        Text("\(event.latitude), \(event.longitude)")
    }.onAppear(perform: { self.locationManager.getUserLocation(into: self.event) })
}
}

struct MapView: UIViewRepresentable {

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

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

func updateUIView(_ uiView: MKMapView, context: Context) { }

final class Coordinator: NSObject, MKMapViewDelegate {
    var control: MapView

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