swift - 如何使用 swiftUI View 在启动时将 Google map 相机聚焦在用户当前位置

Question

我正在尝试制作一个使用 Google map 的应用，并在打开应用时重点关注用户的位置。

现在我已经初始化了 map ，按下 GoogleMaps 固有的“myLocation”按钮后，我能够聚焦于用户位置，但 map 的相机始终聚焦于指定位置，而不是用户位置。

我使用了这两个教程来达到我现在的水平:-https://developers.google.com/maps/documentation/ios-sdk/start-https://www.raywenderlich.com/197-google-maps-ios-sdk-tutorial-getting-started

搜索 Google 和此处后，似乎我需要利用 CLLocationManager() 来获取用户的设备坐标，然后以某种方式使用它？我认为我关于 CLLocationManager() 的代码可能放置在错误的文件中或使用不正确，但我没有收到任何错误。

我的代码是这样工作的:SceneDelegate.swift 将我的 LandmarkList.swift 设置为 rootViewController。然后 LandmarkList 调用 GoogMapView.swift 来显示 Google map 的实例。

SceneDelegate.swift:

我认为我在这里使用 locationManager 可能是错误的？

import UIKit
import SwiftUI
import GoogleMaps
import GooglePlaces
import CoreLocation



class SceneDelegate: UIResponder, UIWindowSceneDelegate, CLLocationManagerDelegate {


    var window: UIWindow?
    private let locationManager = CLLocationManager()


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

        // Use a UIHostingController as window root view controller
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: LandmarkList())
            self.window = window
            window.makeKeyAndVisible()
        }

        locationManager.requestAlwaysAuthorization()

        if CLLocationManager.locationServicesEnabled() {
            locationManager.delegate = self
            locationManager.desiredAccuracy = kCLLocationAccuracyBest
            locationManager.requestWhenInUseAuthorization()
        }

    }
}

LandmarkList.swift:

import SwiftUI

struct LandmarkList: View {

    @State private var searchText = ""
    @State private var locationText = ""


    var body: some View {


            ZStack(alignment: Alignment.top) {
                GoogMapView()
                    .frame(height: 750)


                SlideOverCard {
                    VStack(alignment: .leading) {
                        List(landmarkData) { landmark in
                            NavigationLink(destination: LandmarkDetail(landmark: landmark)) {
                                LandmarkRow(landmark: landmark)
                            }
                        }

                    }
                        .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: .infinity, alignment: Alignment.topLeading)
                    }
        }
    }
}

GoogMapView.swift:

注意:下面的打印语句仅返回“用户位置未知”

import SwiftUI
import UIKit
import GoogleMaps
import GooglePlaces
import CoreLocation


struct GoogMapView : UIViewRepresentable {

        let marker : GMSMarker = GMSMarker()

        //Creates a `UIView` instance to be presented.
        func makeUIView(context: Context) -> GMSMapView {
            // Create a GMSCameraPosition
            let camera = GMSCameraPosition.camera(withLatitude: 42.361145, longitude: -71.057083, zoom: 16.0)
            let mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
            mapView.setMinZoom(14, maxZoom: 20)
            mapView.settings.compassButton = true
            mapView.isMyLocationEnabled = true
            mapView.settings.myLocationButton = true
            mapView.settings.scrollGestures = true
            mapView.settings.zoomGestures = true
            mapView.settings.rotateGestures = true
            mapView.settings.tiltGestures = true
            mapView.isIndoorEnabled = false

            if let mylocation = mapView.myLocation {
              print("User's location: \(mylocation)")
            } else {
              print("User's location is unknown")
            }

            return mapView
        }

//        Updates the presented `UIView` (and coordinator) to the latestconfiguration.
    func updateUIView(_ mapView: GMSMapView, context: Context) {
        // Creates a marker in the center of the map.
        marker.position = CLLocationCoordinate2D(latitude: 42.361145, longitude: -71.057083)
        marker.title = "Boston"
        marker.snippet = "USA"
        marker.map = mapView
    }
}

同样，我认为 SceneDelegate.swift 中有关 locationManager 的代码将使 GoogleMaps 相机实例在启动时聚焦于用户位置，但事实并非如此。

有人知道我做错了什么吗？

Answer 1

我终于能够弄清楚如何立即关注“我的位置”，而不是要求用户输入。以下是更多详细信息...希望有帮助!

更新UIView

• 您希望在检索用户位置时调用 updateUIView。据我所知，当 @State 或 @Binding 对象更改(或 @ObservedObject)时，会调用 updateUIView 。因此，UIViewRepresentable 需要具有其中之一。在下面的代码中，我使用 @ObservedObject。每当 @ObservedObject 的 @Published 属性之一发生更改时，updateUIView 将被调用。

创建观察对象

• 我创建了一个符合 ObservableObject 协议(protocol)的类 (LocationManager)。

• 在类中，我将 lastKnownLocation 公开为 @Published 属性。如上所述，当更新 lastKnownLocation 时，LocationManager 类实例的任何订阅者都将看到这些更新

获取用户坐标

• CLLocationManager 用于获取用户位置的更新。

• 我创建的 LocationManager 类实现了 CLLocationManager

的委托(delegate)函数

• 当用户的位置更新时，将调用委托(delegate)函数didUpdateLocations。然后，在该函数中，我更新 @Published 属性，以便 UIViewRepresentable 看到这些更改，并相应地自动调用 updateUIView。

UIViewRepresentable

import SwiftUI
import GoogleMaps
import Combine

struct HomeView: UIViewRepresentable {

    // Listen to changes on the locationManager
    @ObservedObject var locationManager = LocationManager()

    func makeUIView(context: Self.Context) -> GMSMapView {

        // Just default the camera to anywhere (this will be overwritten as soon as myLocation is grabbed
        let camera = GMSCameraPosition.camera(withLatitude: 0, longitude: 0, zoom: 16.0)
        let mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
        mapView.setMinZoom(14, maxZoom: 20)
        mapView.settings.compassButton = true
        mapView.isMyLocationEnabled = true
        mapView.settings.myLocationButton = true
        mapView.settings.scrollGestures = true
        mapView.settings.zoomGestures = true
        mapView.settings.rotateGestures = true
        mapView.settings.tiltGestures = true
        mapView.isIndoorEnabled = false

        return mapView
    }

    func updateUIView(_ mapView: GMSMapView, context: Self.Context) {

        // When the locationManager publishes updates, respond to them
        if let myLocation = locationManager.lastKnownLocation {
            mapView.animate(toLocation: myLocation.coordinate)
            print("User's location: \(myLocation)")
        }
    }
}

LocationManager 类:

class LocationManager: NSObject, CLLocationManagerDelegate, ObservableObject {

    // Publish the user's location so subscribers can react to updates
    @Published var lastKnownLocation: CLLocation? = nil
    private let manager = CLLocationManager()

    override init() {
        super.init()
        self.manager.delegate = self
        self.manager.startUpdatingLocation()
    }

    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        if status == .authorizedWhenInUse {
            self.manager.startUpdatingLocation()
        }
    }

    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        // Notify listeners that the user has a new location
        self.lastKnownLocation = locations.last
    }
}