Google Maps API：获取当前位置 iOS 的坐标

Question

我目前正在我的项目中使用 Google Maps API。我正在尝试将默认相机/缩放设置为用户位置。我这样做：

@implementation ViewController{

GMSMapView *mapView_;

}
@synthesize currentLatitude,currentLongitude;

- (void)viewDidLoad
{
[super viewDidLoad];
mapView_.settings.myLocationButton = YES;
mapView_.myLocationEnabled = YES;


}
- (void)loadView{

CLLocation *myLocation = mapView_.myLocation;

GMSMarker *marker = [[GMSMarker alloc] init];
marker.position = CLLocationCoordinate2DMake(myLocation.coordinate.latitude, myLocation.coordinate.longitude);
marker.title = @"Current Location";
marker.map = mapView_;
GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:myLocation.coordinate.latitude
                                                        longitude:myLocation.coordinate.longitude
                                                             zoom:6];
mapView_ = [GMSMapView mapWithFrame:CGRectZero camera:camera];

self.view = mapView_;
   NSLog(@"%f, %f", myLocation.coordinate.latitude, myLocation.coordinate.longitude);

}

但是，它不起作用，因为当我这样做时

NSLog(@"%f, %f", myLocation.coordinate.latitude, myLocation.coordinate.longitude);

它返回 0, 0，并且不给出当前位置坐标。如何正确获取用户坐标？

Answer 1

.h

#import <CoreLocation/CoreLocation.h>
@property(nonatomic,retain) CLLocationManager *locationManager;

.m

- (NSString *)deviceLocation 
{
NSString *theLocation = [NSString stringWithFormat:@"latitude: %f longitude: %f", locationManager.location.coordinate.latitude, locationManager.location.coordinate.longitude];
return theLocation;
}

- (void)viewDidLoad
{
    locationManager = [[CLLocationManager alloc] init];
    locationManager.distanceFilter = kCLDistanceFilterNone; 
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; // 100 m
    [locationManager startUpdatingLocation];
}

已回复here。

Answer 2

当应用首次启动时，它可能还不知道您的位置，因为 GPS 设备通常需要一段时间才能锁定您的位置（如果它刚刚启动），尤其是如果这是第一次应用程序已运行，因此用户尚未回答让应用程序访问其位置的提示。此外，在刚刚创建地图视图时，mapView.myLocation 似乎始终为空（nil 或坐标 0,0）。

所以你需要等到知道用户的位置后，再更新摄像头位置。

一种方法可能是使用 Puneet 建议的 how to get current location in google map sdk in iphone 的代码，但请注意，那里的示例代码缺少设置位置管理器的详细信息（例如设置位置管理器的委托），这可能就是它的原因不适合你。

另一种选择是在 mapView.myLocation 上使用 KVO，如下所述：about positioning myself,some problems

顺便说一下，在您的示例代码中，您在创建 mapView 之前访问了 mapView.myLocation，因此无论如何该位置始终为零。

Answer 3

我刚刚下载了适用于 iOS 的新 GoogleMap SDK 演示。这是我从源代码中看到的，“当前位置”是如何通过 KVO 实现的。

#if !defined(__has_feature) || !__has_feature(objc_arc)
#error "This file requires ARC support."
#endif

#import "SDKDemos/Samples/MyLocationViewController.h"

#import <GoogleMaps/GoogleMaps.h>

@implementation MyLocationViewController {
  GMSMapView *mapView_;
  BOOL firstLocationUpdate_;
}

- (void)viewDidLoad {
  [super viewDidLoad];
  GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:-33.868
                                                          longitude:151.2086
                                                               zoom:12];

  mapView_ = [GMSMapView mapWithFrame:CGRectZero camera:camera];
  mapView_.settings.compassButton = YES;
  mapView_.settings.myLocationButton = YES;

  // Listen to the myLocation property of GMSMapView.
  [mapView_ addObserver:self
             forKeyPath:@"myLocation"
                options:NSKeyValueObservingOptionNew
                context:NULL];

  self.view = mapView_;

  // Ask for My Location data after the map has already been added to the UI.
  dispatch_async(dispatch_get_main_queue(), ^{
    mapView_.myLocationEnabled = YES;
  });
}

- (void)dealloc {
  [mapView_ removeObserver:self
                forKeyPath:@"myLocation"
                   context:NULL];
}

#pragma mark - KVO updates

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context {
  if (!firstLocationUpdate_) {
    // If the first location update has not yet been recieved, then jump to that
    // location.
    firstLocationUpdate_ = YES;
    CLLocation *location = [change objectForKey:NSKeyValueChangeNewKey];
    mapView_.camera = [GMSCameraPosition cameraWithTarget:location.coordinate
                                                     zoom:14];
  }
}

@end

希望对你有帮助。

Answer 4

以防万一有人想要 DrDev 在 Swift 3 中的出色答案：

var locationManager: CLLocationManager?

func deviceLocation() -> String {
    let theLocation: String = "latitude: \(locationManager.location.coordinate.latitude) longitude: \(locationManager.location.coordinate.longitude)"
    return theLocation
}

func viewDidLoad() {
    locationManager = CLLocationManager()
    locationManager.distanceFilter = kCLDistanceFilterNone
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters
    // 100 m
    locationManager.startUpdatingLocation()
}