在屏幕上显示用户位置时出现问题答案

【问题标题】：Problem displaying user location on screen在屏幕上显示用户位置时出现问题
【发布时间】：2021-07-16 14:30:45
【问题描述】：

我正在尝试在屏幕上显示用户位置坐标，但当我运行应用程序时没有任何显示，即使我可以在控制台中看到坐标。我遇到的第二个问题是当我按下停止按钮时，位置更新不会停止。

位置管理器：

import Foundation
import CoreLocation

class LocationManager: NSObject, ObservableObject, CLLocationManagerDelegate{
    let locationManager = CLLocationManager()
    @Published var location: CLLocationCoordinate2D?
    
    override init(){
        super.init()
        locationManager.delegate = self
    }
    
    func startTracking() {
        locationManager.requestAlwaysAuthorization()
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.distanceFilter = kCLDistanceFilterNone
        locationManager.allowsBackgroundLocationUpdates = true
        locationManager.startUpdatingLocation()
    }
    
    func stopTracking() {
        print("stop test")
        locationManager.stopUpdatingLocation()
        locationManager.allowsBackgroundLocationUpdates = false
    }
    
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        let tempLocation = locations.last?.coordinate
        print(tempLocation)
        DispatchQueue.main.async {
            self.location = tempLocation
        }
    }
}

查看：

import SwiftUI
struct ContentView: View {
    @StateObject var locationManager = LocationManager()
    
    var body: some View {
        VStack{
            startLocationTrackingButton()
            stopLocationTrackingButton()
            
            if let location = locationManager.location {
                Text("Your location: \(location.latitude), \(location.longitude)")
            }
            
        }
    }
}
struct startLocationTrackingButton: View{
    @StateObject var locationManager = LocationManager()
    
    var body: some View{
        Button("START"){
            locationManager.startTracking()
            
        }
    }
}
struct stopLocationTrackingButton: View{
    @StateObject var locationManager = LocationManager()
    
    var body: some View{
        Button("STOP"){
            locationManager.stopTracking()
        }
    }
}

感谢您的帮助！

【问题讨论】：

标签： swift swiftui core-location

【解决方案1】：

您的每个视图都有：

@StateObject var locationManager = LocationManager()

您正在为每个人创建一个不同的位置管理器。尝试这样做：

truct ContentView: View {
    @StateObject var locationManager = LocationManager()
    
    var body: some View {
        VStack{
            StartLocationTrackingButton(manager: locationManager)
            StopLocationTrackingButton(manager: locationManager)
            
            if let location = locationManager.location {
                Text("Your location: \(location.latitude), \(location.longitude)")
            }
            
        }
    }
}
struct StartLocationTrackingButton: View{
    @ObservedObject var manager: LocationManager
    
    var body: some View{
        Button("START"){
            manager.startTracking()
            
        }
    }
}
struct stopLocationTrackingButton: View{
    @ObservedObject var manager: LocationManager
    
    var body: some View{
        Button("STOP"){
            manager.stopTracking()
        }
    }
}

仅在创建和拥有对象时使用@StateObject。如果您将ObservableObject 传递给另一个视图，则该视图应将其声明为@ObservedObject，并且不要给它一个初始值。

【讨论】：