在地图上选择当前地点并显示详细信息

本教程演示了如何构建一个 iOS 应用，该应用可检索设备的当前位置、识别可能的位置、提示用户选择最匹配的位置，并为所选位置显示地图标记。

适合对 Swift 或 Objective-C 有初级或中级了解，并对 Xcode 有一般了解的人士。有关创建地图的高级指南，请参阅开发者指南。

您将在本教程的指导下创建以下地图。地图标记位于加利福尼亚州旧金山，但会移动到设备或模拟器所在的任何位置。

本教程使用 Places SDK for iOS、Maps SDK for iOS 和 Apple Core Location 框架。

获取代码

从 GitHub 克隆或下载 Google Maps iOS 示例代码库。

或者，您也可以点击下面的按钮，下载源代码：

获取代码

MapViewController

Swift

import UIKit
import GoogleMaps
import GooglePlaces

class MapViewController: UIViewController {

  var locationManager: CLLocationManager!
  var currentLocation: CLLocation?
  var mapView: GMSMapView!
  var placesClient: GMSPlacesClient!
  var preciseLocationZoomLevel: Float = 15.0
  var approximateLocationZoomLevel: Float = 10.0

  // An array to hold the list of likely places.
  var likelyPlaces: [GMSPlace] = []

  // The currently selected place.
  var selectedPlace: GMSPlace?

  // Update the map once the user has made their selection.
  @IBAction func unwindToMain(segue: UIStoryboardSegue) {
    // Clear the map.
    mapView.clear()

    // Add a marker to the map.
    if let place = selectedPlace {
      let marker = GMSMarker(position: place.coordinate)
      marker.title = selectedPlace?.name
      marker.snippet = selectedPlace?.formattedAddress
      marker.map = mapView
    }

    listLikelyPlaces()
  }

  override func viewDidLoad() {
    super.viewDidLoad()

    // Initialize the location manager.
    locationManager = CLLocationManager()
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.requestWhenInUseAuthorization()
    locationManager.distanceFilter = 50
    locationManager.startUpdatingLocation()
    locationManager.delegate = self

    placesClient = GMSPlacesClient.shared()

    // A default location to use when location permission is not granted.
    let defaultLocation = CLLocation(latitude: -33.869405, longitude: 151.199)

    // Create a map.
    let zoomLevel = locationManager.accuracyAuthorization == .fullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel
    let camera = GMSCameraPosition.camera(withLatitude: defaultLocation.coordinate.latitude,
                                          longitude: defaultLocation.coordinate.longitude,
                                          zoom: zoomLevel)
    let options = GMSMapViewOptions()
    options.camera = camera
    options.frame = view.bounds
    mapView = GMSMapView(options: options)
    mapView.settings.myLocationButton = true
    mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    mapView.isMyLocationEnabled = true

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

    listLikelyPlaces()
  }

  // Populate the array with the list of likely places.
  func listLikelyPlaces() {
    // Clean up from previous sessions.
    likelyPlaces.removeAll()

    let placeFields: GMSPlaceField = [.name, .coordinate]
    placesClient.findPlaceLikelihoodsFromCurrentLocation(withPlaceFields: placeFields) { (placeLikelihoods, error) in
      guard error == nil else {
        // TODO: Handle the error.
        print("Current Place error: \(error!.localizedDescription)")
        return
      }

      guard let placeLikelihoods = placeLikelihoods else {
        print("No places found.")
        return
      }

      // Get likely places and add to the list.
      for likelihood in placeLikelihoods {
        let place = likelihood.place
        self.likelyPlaces.append(place)
      }
    }
  }

  // Prepare the segue.
  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "segueToSelect" {
      if let nextViewController = segue.destination as? PlacesViewController {
        nextViewController.likelyPlaces = likelyPlaces
      }
    }
  }
}

// Delegates to handle events for the location manager.
extension MapViewController: CLLocationManagerDelegate {

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

    let zoomLevel = locationManager.accuracyAuthorization == .fullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel
    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)
    }

    listLikelyPlaces()
  }

  // Handle authorization for the location manager.
  func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
    // Check accuracy authorization
    let accuracy = manager.accuracyAuthorization
    switch accuracy {
    case .fullAccuracy:
        print("Location accuracy is precise.")
    case .reducedAccuracy:
        print("Location accuracy is not precise.")
    @unknown default:
      fatalError()
    }

    // Handle authorization status
    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.")
    @unknown default:
      fatalError()
    }
  }

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

Objective-C

#import "MapViewController.h"
#import "PlacesViewController.h"
@import CoreLocation;
@import GooglePlaces;
@import GoogleMaps;

@interface MapViewController () <CLLocationManagerDelegate>

@end

@implementation MapViewController {
  CLLocationManager *locationManager;
  CLLocation * _Nullable currentLocation;
  GMSMapView *mapView;
  GMSPlacesClient *placesClient;
  float preciseLocationZoomLevel;
  float approximateLocationZoomLevel;

  // An array to hold the list of likely places.
  NSMutableArray<GMSPlace *> *likelyPlaces;

  // The currently selected place.
  GMSPlace * _Nullable selectedPlace;
}

- (void)viewDidLoad {
  [super viewDidLoad];
  preciseLocationZoomLevel = 15.0;
  approximateLocationZoomLevel = 15.0;

  // Initialize the location manager.
  locationManager = [[CLLocationManager alloc] init];
  locationManager.desiredAccuracy = kCLLocationAccuracyBest;
  [locationManager requestWhenInUseAuthorization];
  locationManager.distanceFilter = 50;
  [locationManager startUpdatingLocation];
  locationManager.delegate = self;

  placesClient = [GMSPlacesClient sharedClient];

  // A default location to use when location permission is not granted.
  CLLocationCoordinate2D defaultLocation = CLLocationCoordinate2DMake(-33.869405, 151.199);

  // Create a map.
  float zoomLevel = locationManager.accuracyAuthorization == CLAccuracyAuthorizationFullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel;
  GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:defaultLocation.latitude
                                                          longitude:defaultLocation.longitude
                                                               zoom:zoomLevel];
  GMSMapViewOptions *options = [[GMSMapViewOptions alloc] init];
  options.camera = camera;
  options.frame = self.view.bounds;
  mapView = [[GMSMapView alloc] initWithOptions:options];
  mapView.settings.myLocationButton = YES;
  mapView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
  mapView.myLocationEnabled = YES;

  // Add the map to the view, hide it until we've got a location update.
  [self.view addSubview:mapView];
  mapView.hidden = YES;

  [self listLikelyPlaces];
}

// Populate the array with the list of likely places.
- (void) listLikelyPlaces
{
  // Clean up from previous sessions.
  likelyPlaces = [NSMutableArray array];

  GMSPlaceField placeFields = GMSPlaceFieldName | GMSPlaceFieldCoordinate;
  [placesClient findPlaceLikelihoodsFromCurrentLocationWithPlaceFields:placeFields callback:^(NSArray<GMSPlaceLikelihood *> * _Nullable likelihoods, NSError * _Nullable error) {
    if (error != nil) {
      // TODO: Handle the error.
      NSLog(@"Current Place error: %@", error.localizedDescription);
      return;
    }

    if (likelihoods == nil) {
      NSLog(@"No places found.");
      return;
    }

    for (GMSPlaceLikelihood *likelihood in likelihoods) {
      GMSPlace *place = likelihood.place;
      [likelyPlaces addObject:place];
    }
  }];
}

// Update the map once the user has made their selection.
- (void) unwindToMain:(UIStoryboardSegue *)segue
{
  // Clear the map.
  [mapView clear];

  // Add a marker to the map.
  if (selectedPlace != nil) {
    GMSMarker *marker = [GMSMarker markerWithPosition:selectedPlace.coordinate];
    marker.title = selectedPlace.name;
    marker.snippet = selectedPlace.formattedAddress;
    marker.map = mapView;
  }

  [self listLikelyPlaces];
}

// Prepare the segue.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
  if ([segue.identifier isEqualToString:@"segueToSelect"]) {
    if ([segue.destinationViewController isKindOfClass:[PlacesViewController class]]) {
      PlacesViewController *placesViewController = (PlacesViewController *)segue.destinationViewController;
      placesViewController.likelyPlaces = likelyPlaces;
    }
  }
}

// Delegates to handle events for the location manager.
#pragma mark - CLLocationManagerDelegate

// Handle incoming location events.
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations
{
  CLLocation *location = locations.lastObject;
  NSLog(@"Location: %@", location);

  float zoomLevel = locationManager.accuracyAuthorization == CLAccuracyAuthorizationFullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel;
  GMSCameraPosition * camera = [GMSCameraPosition cameraWithLatitude:location.coordinate.latitude
                                                           longitude:location.coordinate.longitude
                                                                zoom:zoomLevel];

  if (mapView.isHidden) {
    mapView.hidden = NO;
    mapView.camera = camera;
  } else {
    [mapView animateToCameraPosition:camera];
  }

  [self listLikelyPlaces];
}

// Handle authorization for the location manager.
- (void)locationManager:(CLLocationManager *)manager didChangeAuthorizationStatus:(CLAuthorizationStatus)status
{
  // Check accuracy authorization
  CLAccuracyAuthorization accuracy = manager.accuracyAuthorization;
  switch (accuracy) {
    case CLAccuracyAuthorizationFullAccuracy:
      NSLog(@"Location accuracy is precise.");
      break;
    case CLAccuracyAuthorizationReducedAccuracy:
      NSLog(@"Location accuracy is not precise.");
      break;
  }

  // Handle authorization status
  switch (status) {
    case kCLAuthorizationStatusRestricted:
      NSLog(@"Location access was restricted.");
      break;
    case kCLAuthorizationStatusDenied:
      NSLog(@"User denied access to location.");
      // Display the map using the default location.
      mapView.hidden = NO;
    case kCLAuthorizationStatusNotDetermined:
      NSLog(@"Location status not determined.");
    case kCLAuthorizationStatusAuthorizedAlways:
    case kCLAuthorizationStatusAuthorizedWhenInUse:
      NSLog(@"Location status is OK.");
  }
}

// Handle location manager errors.
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
  [manager stopUpdatingLocation];
  NSLog(@"Error: %@", error.localizedDescription);
}

@end
      

PlacesViewController

Swift

import UIKit
import GooglePlaces

class PlacesViewController: UIViewController {

  // ...

  // Pass the selected place to the new view controller.
  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "unwindToMain" {
      if let nextViewController = segue.destination as? MapViewController {
        nextViewController.selectedPlace = selectedPlace
      }
    }
  }
}

// Respond when a user selects a place.
extension PlacesViewController: UITableViewDelegate {
  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    selectedPlace = likelyPlaces[indexPath.row]
    performSegue(withIdentifier: "unwindToMain", sender: self)
  }

  // Adjust cell height to only show the first five items in the table
  // (scrolling is disabled in IB).
  func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return self.tableView.frame.size.height/5
  }

  // Make table rows display at proper height if there are less than 5 items.
  func tableView(_ tableView: UITableView, heightForFooterInSection section: Int) -> CGFloat {
    if (section == tableView.numberOfSections - 1) {
      return 1
    }
    return 0
  }
}

// Populate the table with the list of most likely places.
extension PlacesViewController: UITableViewDataSource {
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return likelyPlaces.count
  }

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: cellReuseIdentifier, for: indexPath)
    let collectionItem = likelyPlaces[indexPath.row]

    cell.textLabel?.text = collectionItem.name

    return cell
  }
}
      

Objective-C

#import "PlacesViewController.h"

@interface PlacesViewController () <UITableViewDataSource, UITableViewDelegate>
// ...

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{

}

#pragma mark - UITableViewDelegate

// Respond when a user selects a place.
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
  self.selectedPlace = [self.likelyPlaces objectAtIndex:indexPath.row];
  [self performSegueWithIdentifier:@"unwindToMain" sender:self];
}

// Adjust cell height to only show the first five items in the table
// (scrolling is disabled in IB).
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
  return self.tableView.frame.size.height/5;
}

// Make table rows display at proper height if there are less than 5 items.
-(CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section
{
  if (section == tableView.numberOfSections - 1) {
    return 1;
  }
  return 0;
}

#pragma mark - UITableViewDataSource

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
  return self.likelyPlaces.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
  return [tableView dequeueReusableCellWithIdentifier:cellReuseIdentifier forIndexPath:indexPath];
}
@end
      

开始使用

注意：已完成教程的示例代码配置为作为 Swift Xcode 项目运行，但包含 Swift 和 Objective-C 示例。

Swift Package Manager

您可以使用 Swift Package Manager 安装 Maps SDK for iOS。

1. 移除所有现有的 Maps SDK for iOS 依赖项。
2. 打开终端窗口并导航至 tutorials/current-place-on-map 目录。
3. 关闭 Xcode 工作区，然后运行以下命令：

           sudo gem install cocoapods-deintegrate cocoapods-clean
           pod deintegrate
           pod cache clean --all
           rm Podfile
           rm current-place-on-map.xcworkspace

4. 打开您的 Xcode 项目，然后删除 podfile。
5. 添加 Places SDK 和 Maps SDK：
1. 前往 File > Add Package Dependencies。
2. 输入 https://github.com/googlemaps/ios-places-sdk 作为网址，按 Enter 键拉取软件包，然后点击 Add Package。
3. 输入 https://github.com/googlemaps/ios-maps-sdk 作为网址，按 Enter 键拉取软件包，然后点击 Add Package（添加软件包）。
6. 您可能需要使用 File > Packages > Reset Package Cache 重置软件包缓存。

获取 API 密钥并启用必要的 API

如需完成本教程，您需要一个已获得 Maps SDK for iOS 和 Places API 使用授权的 Google API 密钥。

1. 按照 Google Maps Platform 使用入门中的说明，设置结算账号和同时启用这两款产品的项目。
2. 按照获取 API 密钥中的说明为之前设置的开发项目创建 API 密钥。

为应用添加API密钥

按照以下方法向 AppDelegate.swift 添加 API 密钥：

1. 请注意，以下 import 语句已添加到该文件中：

   import GooglePlaces
   import GoogleMaps

2. 修改 application(_:didFinishLaunchingWithOptions:) 方法中的以下行，并将其中的“YOUR_API_KEY”替换为您的 API 密钥：YOUR_API_KEY

   GMSPlacesClient.provideAPIKey("YOUR_API_KEY")
   GMSServices.provideAPIKey("YOUR_API_KEY")

注意： 根据 您的配置，Maps SDK API 密钥可能与 Places SDK API 密钥的值相同。

构建并运行应用

1. 将 iOS 设备连接到计算机，或者从 Xcode 方案菜单中选择一个模拟器。
2. 如果您使用的是设备，请确保位置信息服务已启用。 如果您使用的是模拟器，请从功能菜单中选择一个位置。
3. 在 Xcode 中，点击 Product/Run 菜单选项（或 play 按钮图标）。
• Xcode 会构建应用，然后在设备或模拟器上运行该应用。
• 您将看到一张地图，该地图会以您当前所在位置为中心显示许多标记。

问题排查：

• 如果您没有看到地图，请检查您是否已按照上文中的说明获取 API 密钥并将其添加到该应用中。在 Xcode 的调试控制台中查看有关 API 密钥的错误消息。
• 如果您已通过 iOS 软件包标识符限制了 API 密钥，请修改该密钥，以便添加该应用的软件包标识符：com.google.examples.current-place-on-map。
• 如果位置信息服务的权限请求被拒绝，地图将无法正常显示。
  • 如果您使用的是设备，请依次前往设置/通用/隐私/位置信息服务，然后重新启用位置信息服务。
  • 如果您使用的是模拟器，请前往模拟器/重置内容和设置…
  下次运行该应用时，请务必接受位置信息服务提示。
• 确保您的 Wi-Fi 或 GPS 连接信号良好。
• 如果应用启动但未显示地图，请确保您已使用相应的位置权限更新项目的 Info.plist。如需详细了解权限处理，请参阅下文有关在应用中请求位置信息权限的指南。
• 使用 Xcode 调试工具查看日志并调试应用。

了解代码

本部分教程介绍了 current-place-on-map 应用最重要的部分，以帮助您了解如何构建类似的应用。

current-place-on-map 应用包含两个视图控制器：一个用于显示地图，其中显示了用户选择的地点；另一个用于向用户显示可能存在的地点列表，供用户从中选择。请注意，每个视图控制器都具有相同的变量，用于跟踪可能地点的列表 (likelyPlaces) 和指示用户的选择 (selectedPlace)。视图之间的导航是通过使用 segue 完成的。

请求位置信息权限

您的应用必须提示用户同意使用位置信息服务。为此，请在应用的 Info.plist 文件中添加 NSLocationAlwaysUsageDescription 键，并将每个键的值设置为一个字符串，用于描述应用打算如何使用位置数据。

设置位置管理器

注意：iOS 14 推出了一项新的隐私保护功能，用户可以选择分享大致位置信息，而不是确切位置信息。检查应用在 CLLocationManager 中的 accuracyAuthorization 值，确保应用的行为符合预期。 观看此视频了解详情。

使用 CLLocationManager 查找设备的当前位置，并在设备移动到新位置时请求定期更新。本教程提供了获取设备位置所需的代码。如需了解详情，请参阅 Apple 开发者文档中的获取用户位置信息指南。

1. 在类级别声明位置管理器、当前位置、地图视图、Places 客户端和默认缩放级别。

Swift

var locationManager: CLLocationManager!
var currentLocation: CLLocation?
var mapView: GMSMapView!
var placesClient: GMSPlacesClient!
var preciseLocationZoomLevel: Float = 15.0
var approximateLocationZoomLevel: Float = 10.0
      

Objective-C

CLLocationManager *locationManager;
CLLocation * _Nullable currentLocation;
GMSMapView *mapView;
GMSPlacesClient *placesClient;
float preciseLocationZoomLevel;
float approximateLocationZoomLevel;
      

2. 在 viewDidLoad() 中初始化位置信息管理器和 GMSPlacesClient。

Swift

// Initialize the location manager.
locationManager = CLLocationManager()
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.requestWhenInUseAuthorization()
locationManager.distanceFilter = 50
locationManager.startUpdatingLocation()
locationManager.delegate = self

placesClient = GMSPlacesClient.shared()
      

Objective-C

// Initialize the location manager.
locationManager = [[CLLocationManager alloc] init];
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager requestWhenInUseAuthorization];
locationManager.distanceFilter = 50;
[locationManager startUpdatingLocation];
locationManager.delegate = self;

placesClient = [GMSPlacesClient sharedClient];
      

3. 声明变量以保存可能地点的列表和用户选择的地点。

Swift

// An array to hold the list of likely places.
var likelyPlaces: [GMSPlace] = []

// The currently selected place.
var selectedPlace: GMSPlace?
      

Objective-C

// An array to hold the list of likely places.
NSMutableArray<GMSPlace *> *likelyPlaces;

// The currently selected place.
GMSPlace * _Nullable selectedPlace;
      

4. 使用扩展子句添加委托，以处理位置信息管理器的事件。

Swift

// Delegates to handle events for the location manager.
extension MapViewController: CLLocationManagerDelegate {

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

    let zoomLevel = locationManager.accuracyAuthorization == .fullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel
    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)
    }

    listLikelyPlaces()
  }

  // Handle authorization for the location manager.
  func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
    // Check accuracy authorization
    let accuracy = manager.accuracyAuthorization
    switch accuracy {
    case .fullAccuracy:
        print("Location accuracy is precise.")
    case .reducedAccuracy:
        print("Location accuracy is not precise.")
    @unknown default:
      fatalError()
    }

    // Handle authorization status
    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.")
    @unknown default:
      fatalError()
    }
  }

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

Objective-C

// Delegates to handle events for the location manager.
#pragma mark - CLLocationManagerDelegate

// Handle incoming location events.
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray<CLLocation *> *)locations
{
  CLLocation *location = locations.lastObject;
  NSLog(@"Location: %@", location);

  float zoomLevel = locationManager.accuracyAuthorization == CLAccuracyAuthorizationFullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel;
  GMSCameraPosition * camera = [GMSCameraPosition cameraWithLatitude:location.coordinate.latitude
                                                           longitude:location.coordinate.longitude
                                                                zoom:zoomLevel];

  if (mapView.isHidden) {
    mapView.hidden = NO;
    mapView.camera = camera;
  } else {
    [mapView animateToCameraPosition:camera];
  }

  [self listLikelyPlaces];
}

// Handle authorization for the location manager.
- (void)locationManager:(CLLocationManager *)manager didChangeAuthorizationStatus:(CLAuthorizationStatus)status
{
  // Check accuracy authorization
  CLAccuracyAuthorization accuracy = manager.accuracyAuthorization;
  switch (accuracy) {
    case CLAccuracyAuthorizationFullAccuracy:
      NSLog(@"Location accuracy is precise.");
      break;
    case CLAccuracyAuthorizationReducedAccuracy:
      NSLog(@"Location accuracy is not precise.");
      break;
  }

  // Handle authorization status
  switch (status) {
    case kCLAuthorizationStatusRestricted:
      NSLog(@"Location access was restricted.");
      break;
    case kCLAuthorizationStatusDenied:
      NSLog(@"User denied access to location.");
      // Display the map using the default location.
      mapView.hidden = NO;
    case kCLAuthorizationStatusNotDetermined:
      NSLog(@"Location status not determined.");
    case kCLAuthorizationStatusAuthorizedAlways:
    case kCLAuthorizationStatusAuthorizedWhenInUse:
      NSLog(@"Location status is OK.");
  }
}

// Handle location manager errors.
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
  [manager stopUpdatingLocation];
  NSLog(@"Error: %@", error.localizedDescription);
}
      

添加地图

创建地图并将其添加到主视图控制器的 viewDidLoad() 中的视图。地图会保持隐藏状态，直到收到位置信息更新（位置信息更新在 CLLocationManagerDelegate 扩展程序中处理）。

Swift

// A default location to use when location permission is not granted.
let defaultLocation = CLLocation(latitude: -33.869405, longitude: 151.199)

// Create a map.
let zoomLevel = locationManager.accuracyAuthorization == .fullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel
let camera = GMSCameraPosition.camera(withLatitude: defaultLocation.coordinate.latitude,
                                      longitude: defaultLocation.coordinate.longitude,
                                      zoom: zoomLevel)
let options = GMSMapViewOptions()
options.camera = camera
options.frame = view.bounds
mapView = GMSMapView(options: options)
mapView.settings.myLocationButton = true
mapView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
mapView.isMyLocationEnabled = true

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

Objective-C

// A default location to use when location permission is not granted.
CLLocationCoordinate2D defaultLocation = CLLocationCoordinate2DMake(-33.869405, 151.199);

// Create a map.
float zoomLevel = locationManager.accuracyAuthorization == CLAccuracyAuthorizationFullAccuracy ? preciseLocationZoomLevel : approximateLocationZoomLevel;
GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:defaultLocation.latitude
                                                        longitude:defaultLocation.longitude
                                                             zoom:zoomLevel];
GMSMapViewOptions *options = [[GMSMapViewOptions alloc] init];
options.camera = camera;
options.frame = self.view.bounds;
mapView = [[GMSMapView alloc] initWithOptions:options];
mapView.settings.myLocationButton = YES;
mapView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
mapView.myLocationEnabled = YES;

// Add the map to the view, hide it until we've got a location update.
[self.view addSubview:mapView];
mapView.hidden = YES;
      

提示用户选择其当前地点

使用 Places SDK for iOS 根据用户的当前位置获取前五名地点可能性，并在 UITableView 中显示该列表。当用户选择某个地点时，向地图添加标记。

1. 获取可能地点的列表以填充 UITableView，用户可以从中选择自己所在的位置。

Swift

// Populate the array with the list of likely places.
func listLikelyPlaces() {
  // Clean up from previous sessions.
  likelyPlaces.removeAll()

  let placeFields: GMSPlaceField = [.name, .coordinate]
  placesClient.findPlaceLikelihoodsFromCurrentLocation(withPlaceFields: placeFields) { (placeLikelihoods, error) in
    guard error == nil else {
      // TODO: Handle the error.
      print("Current Place error: \(error!.localizedDescription)")
      return
    }

    guard let placeLikelihoods = placeLikelihoods else {
      print("No places found.")
      return
    }

    // Get likely places and add to the list.
    for likelihood in placeLikelihoods {
      let place = likelihood.place
      self.likelyPlaces.append(place)
    }
  }
}
      

Objective-C

// Populate the array with the list of likely places.
- (void) listLikelyPlaces
{
  // Clean up from previous sessions.
  likelyPlaces = [NSMutableArray array];

  GMSPlaceField placeFields = GMSPlaceFieldName | GMSPlaceFieldCoordinate;
  [placesClient findPlaceLikelihoodsFromCurrentLocationWithPlaceFields:placeFields callback:^(NSArray<GMSPlaceLikelihood *> * _Nullable likelihoods, NSError * _Nullable error) {
    if (error != nil) {
      // TODO: Handle the error.
      NSLog(@"Current Place error: %@", error.localizedDescription);
      return;
    }

    if (likelihoods == nil) {
      NSLog(@"No places found.");
      return;
    }

    for (GMSPlaceLikelihood *likelihood in likelihoods) {
      GMSPlace *place = likelihood.place;
      [likelyPlaces addObject:place];
    }
  }];
}
      

2. 打开一个新版视图，向用户呈现可能的位置。当用户点按“获取地点”时，我们会切换到新版视图，并向用户显示可供选择的地点列表。prepare 函数会使用当前可能的位置列表更新 PlacesViewController，并在执行转场时自动调用。

Swift

// Prepare the segue.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
  if segue.identifier == "segueToSelect" {
    if let nextViewController = segue.destination as? PlacesViewController {
      nextViewController.likelyPlaces = likelyPlaces
    }
  }
}
      

Objective-C

// Prepare the segue.
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
  if ([segue.identifier isEqualToString:@"segueToSelect"]) {
    if ([segue.destinationViewController isKindOfClass:[PlacesViewController class]]) {
      PlacesViewController *placesViewController = (PlacesViewController *)segue.destinationViewController;
      placesViewController.likelyPlaces = likelyPlaces;
    }
  }
}
      

3. 在 PlacesViewController 中，使用最有可能的地点列表填充表格，使用 UITableViewDataSource 委托扩展程序。

Swift

// Populate the table with the list of most likely places.
extension PlacesViewController: UITableViewDataSource {
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return likelyPlaces.count
  }

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: cellReuseIdentifier, for: indexPath)
    let collectionItem = likelyPlaces[indexPath.row]

    cell.textLabel?.text = collectionItem.name

    return cell
  }
}
      

Objective-C

#pragma mark - UITableViewDataSource

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
  return self.likelyPlaces.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
  return [tableView dequeueReusableCellWithIdentifier:cellReuseIdentifier forIndexPath:indexPath];
}
@end
      

4. 使用 UITableViewDelegate 委托扩展程序处理用户的选择。

Swift

class PlacesViewController: UIViewController {

  // ...

  // Pass the selected place to the new view controller.
  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "unwindToMain" {
      if let nextViewController = segue.destination as? MapViewController {
        nextViewController.selectedPlace = selectedPlace
      }
    }
  }
}

// Respond when a user selects a place.
extension PlacesViewController: UITableViewDelegate {
  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    selectedPlace = likelyPlaces[indexPath.row]
    performSegue(withIdentifier: "unwindToMain", sender: self)
  }

  // Adjust cell height to only show the first five items in the table
  // (scrolling is disabled in IB).
  func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return self.tableView.frame.size.height/5
  }

  // Make table rows display at proper height if there are less than 5 items.
  func tableView(_ tableView: UITableView, heightForFooterInSection section: Int) -> CGFloat {
    if (section == tableView.numberOfSections - 1) {
      return 1
    }
    return 0
  }
}
      

Objective-C

@interface PlacesViewController () <UITableViewDataSource, UITableViewDelegate>
// ...

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{

}

#pragma mark - UITableViewDelegate

// Respond when a user selects a place.
-(void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
  self.selectedPlace = [self.likelyPlaces objectAtIndex:indexPath.row];
  [self performSegueWithIdentifier:@"unwindToMain" sender:self];
}

// Adjust cell height to only show the first five items in the table
// (scrolling is disabled in IB).
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
  return self.tableView.frame.size.height/5;
}

// Make table rows display at proper height if there are less than 5 items.
-(CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section
{
  if (section == tableView.numberOfSections - 1) {
    return 1;
  }
  return 0;
}
      

向地图添加标记

当用户做出选择时，使用展开的 segue 返回到上一个视图，并将标记添加到地图。返回到主视图控制器时，系统会自动调用 unwindToMain IBAction。

Swift

// Update the map once the user has made their selection.
@IBAction func unwindToMain(segue: UIStoryboardSegue) {
  // Clear the map.
  mapView.clear()

  // Add a marker to the map.
  if let place = selectedPlace {
    let marker = GMSMarker(position: place.coordinate)
    marker.title = selectedPlace?.name
    marker.snippet = selectedPlace?.formattedAddress
    marker.map = mapView
  }

  listLikelyPlaces()
}
      

Objective-C

// Update the map once the user has made their selection.
- (void) unwindToMain:(UIStoryboardSegue *)segue
{
  // Clear the map.
  [mapView clear];

  // Add a marker to the map.
  if (selectedPlace != nil) {
    GMSMarker *marker = [GMSMarker markerWithPosition:selectedPlace.coordinate];
    marker.title = selectedPlace.name;
    marker.snippet = selectedPlace.formattedAddress;
    marker.map = mapView;
  }

  [self listLikelyPlaces];
}
      

恭喜！您已构建了一个 iOS 应用，该应用可让用户选择其当前地点，并在 Google 地图上显示结果。在此过程中，您学习了如何使用 Places SDK for iOS、Maps SDK for iOS 和 Apple Core Location 框架。