How to focus Google Maps camera on user's current location at startup using swiftUI views

I was finally able to figure out how to focus on "my location" immediately, instead of requiring input from the user. Here are some more details...hope it helps!

updateUIView

• You want updateUIView to be called when the user's location is retrieved. From what I have read updateUIView is called when a @State or @Binding object changes (or @ObservedObject). So, the UIViewRepresentable needs to have one of these. In the case of my code below, I use an @ObservedObject. Whenever one of the @ObservedObject's @Published properties changes, updateUIView will be called.

Creating The Observed Object

• I created a class (LocationManager) that conforms to the ObservableObject protocol.

• Within the class, I exposed the lastKnownLocation as a @Published property. As mentioned above, when the lastKnownLocation is updated, any subscribers to an instance of the LocationManager class will see those updates

Getting The User's Coordinates

• CLLocationManager is used to get updates on the user's location.

• The LocationManager class I created implements the delegate functions for CLLocationManager

• The delegate function didUpdateLocations is called when the user's location is updated. Within that function, I then update the @Published property so that the UIViewRepresentable sees those changes, and updateUIView is automatically called accordingly.

The 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)")
        }
    }
}

The LocationManager class:

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
    }
}

Using comments here and others on StackOverflow, I made this solution:

//
//  GoogMapView.swift
//  Landmarks
//
//  Created by Zahr Lyttle on 10/14/19.
//  Copyright © 2019 Apple. All rights reserved.
//

import SwiftUI
import UIKit
import GoogleMaps
import GooglePlaces
import CoreLocation
import Foundation



struct GoogMapView: View {
    var body: some View {
        GoogMapControllerRepresentable()
    }
}


class GoogMapController: UIViewController, CLLocationManagerDelegate {
    var locationManager = CLLocationManager()
    var mapView: GMSMapView!
    let defaultLocation = CLLocation(latitude: 42.361145, longitude: -71.057083)
    var zoomLevel: Float = 15.0
    let marker : GMSMarker = GMSMarker()


    override func viewDidLoad() {
        super.viewDidLoad()

        locationManager = CLLocationManager()
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.requestAlwaysAuthorization()
        locationManager.distanceFilter = 50
        locationManager.startUpdatingLocation()
        locationManager.delegate = self

        let camera = GMSCameraPosition.camera(withLatitude: defaultLocation.coordinate.latitude, longitude: defaultLocation.coordinate.longitude, zoom: zoomLevel)
        mapView = GMSMapView.map(withFrame: view.bounds, camera: camera)
        mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        mapView.isMyLocationEnabled = true
        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")
//        }

        marker.position = CLLocationCoordinate2D(latitude: 42.361145, longitude: -71.057083)
        marker.title = "Boston"
        marker.snippet = "USA"
        marker.map = mapView

        // Add the map to the view, hide it until we've got a location update.
        view.addSubview(mapView)
//        mapView.isHidden = true

    }

    // Handle incoming location events.
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
      let location: CLLocation = locations.last!
      print("Location: \(location)")

      let camera = GMSCameraPosition.camera(withLatitude: location.coordinate.latitude, longitude: location.coordinate.longitude, zoom: zoomLevel)

      if mapView.isHidden {
        mapView.isHidden = false
        mapView.camera = camera
      } else {
        mapView.animate(to: camera)
      }

    }

    // Handle authorization for the location manager.
    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
      switch status {
      case .restricted:
        print("Location access was restricted.")
      case .denied:
        print("User denied access to location.")
        // Display the map using the default location.
        mapView.isHidden = false
      case .notDetermined:
        print("Location status not determined.")
      case .authorizedAlways: fallthrough
      case .authorizedWhenInUse:
        print("Location status is OK.")
      }
    }

    // Handle location manager errors.
    func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
      locationManager.stopUpdatingLocation()
      print("Error: \(error)")
    }

}


struct GoogMapControllerRepresentable: UIViewControllerRepresentable {
    func makeUIViewController(context: UIViewControllerRepresentableContext<GMControllerRepresentable>) -> GMController {
        return GMController()
    }

    func updateUIViewController(_ uiViewController: GMController, context: UIViewControllerRepresentableContext<GMControllerRepresentable>) {

    }
}

You can implement this by "pretending" your View is a ViewController. Try setting GoogleMapView as the delegate, instead. Then put your initialization code in makeUIView and then conform to the protocol:

struct GoogMapView : CLLocationManagerDelegate {

private let locationManager = CLLocationManager()

  func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {

    guard status == .authorizedWhenInUse else {
      return
    }

    locationManager.startUpdatingLocation()


    mapView.isMyLocationEnabled = true
    mapView.settings.myLocationButton = true
  }


  func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    guard let location = locations.first else {
      return
    }


    mapView.camera = GMSCameraPosition(target: location.coordinate, zoom: 15, bearing: 0, viewingAngle: 0)


    locationManager.stopUpdatingLocation()
  }
}

Above taken from https://www.raywenderlich.com/197-google-maps-ios-sdk-tutorial-getting-started.