试图在内容视图中使用SwiftUI获取用户位置，但显示为零

Question

我是一个初学者，试图从LocationManager获取纬度和经度，并使用SwiftUI在ContentView中显示，但结果显示为零。但是控制台会打印LocationManager类中的数据。不显示内容视图中的纬度和经度。有人能帮忙吗？(Xcode 11(

这是LocationManager类

import Foundation
import CoreLocation
import Combine
class LocationManager: NSObject,CLLocationManagerDelegate, ObservableObject {
private let manager: CLLocationManager
var willChange = PassthroughSubject<LocationManager, Never>()
var getLat: String = ""
var getLon: String = ""
var lastKnownLocation: CLLocation? {
willSet {
willChange.send(self)
}
}
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
if status == .denied {
print("denied")
}
else{
print("athorized")
manager.requestLocation()
}
}
func start() {
manager.requestWhenInUseAuthorization()
manager.startUpdatingLocation()
}
init(manager: CLLocationManager = CLLocationManager()) {
self.manager = manager
super.init()
}
func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
print(error.localizedDescription)
}
func startUpdating() {
self.manager.delegate = self
self.manager.requestWhenInUseAuthorization()
self.manager.startUpdatingLocation()
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
//print(locations)
lastKnownLocation = locations.last

getLat = "(locations.last!.coordinate.latitude)"
getLon = "(locations.last!.coordinate.longitude)"

showLocation()
}
func showLocation() {
print("from showLocation")
print("Latitude: (getLat)")
print("Longitude: (getLon)")
}

}

这是显示LocationManager类的纬度和经度的控制台

这是内容视图

import SwiftUI
import CoreLocation
struct ContentView: View {
@State var managerDelegate = LocationManager()
@State var manager = CLLocationManager()
@ObservedObject var location = LocationManager()
var lat: String {
return "(location.lastKnownLocation?.coordinate.latitude ?? 0.0)"
}
var lon: String {
return "(location.lastKnownLocation?.coordinate.longitude ?? 0.0)"
}
init() {
self.manager.delegate = self.managerDelegate
do {
try self.manager.requestAlwaysAuthorization()
}
catch {
print(error.localizedDescription)
self.manager.requestAlwaysAuthorization()
}
}
var body: some View {
VStack {
Text("Hello, World")
Text("Latitude: (lat)")
Text("Longitude: (lon)")
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

这是模拟器中ContentView的输出

Answer 1

好吧，我发现自己有时间阅读您的代码，我有一个解决方案。

首先，您需要将委托设置为ContentView.init():中您正在观察的变量

self.manager.delegate = self.location

之后，您需要立即调用在LocationManager:中定义的startUpdating()函数

self.location.startUpdating()

最后，您可能想要删除will-change实现，并选择更简单的：

@Published var lastKnownLocation: CLLocation?

已发布的包装器将自动为您触发对象更改。

---

Refactor

现在，如果您愿意，还可以将init语句缩减为一行：

init() {
self.location.startUpdating()
}

这意味着您可以自由删除几个属性：

`@State var managerDelegate = LocationManager()`
`@State var manager = CLLocationManager()`

---

TLDR这是代码的缩短版本：

内容视图

import SwiftUI
struct ContentView: View {
@ObservedObject var location = LocationManager()
var lat: String {
return "(location.lastKnownLocation?.coordinate.latitude ?? 0.0)"
}
var lon: String {
return "(location.lastKnownLocation?.coordinate.longitude ?? 0.0)"
}
init() {
self.location.startUpdating()
}
var body: some View {
VStack {
Text("Location breakdown")
Text("Latitude: (lat)")
Text("Longitude: (lon)")
}
.padding()
.padding()
.background(Color.white)
.cornerRadius(10)
.shadow(radius: 10)
}
}

仓位经理

import Foundation
import CoreLocation
class LocationManager: NSObject, CLLocationManagerDelegate, ObservableObject {
private let manager = CLLocationManager()
@Published var lastKnownLocation: CLLocation?

func startUpdating() {
self.manager.delegate = self
self.manager.requestWhenInUseAuthorization()
self.manager.startUpdatingLocation()
}

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
lastKnownLocation = locations.last

}

}