Select platform: [Android](https://developers.google.com/maps/documentation/android-sdk/events.md.txt "View this page for the Android platform docs.") [iOS](https://developers.google.com/maps/documentation/ios-sdk/events.md.txt "View this page for the iOS platform docs.") [JavaScript](https://developers.google.com/maps/documentation/javascript/events.md.txt "View this page for the JavaScript platform docs.")
Using the Maps SDK for iOS, you can listen to events that occur on the map, such as camera change events or marker tap events. ## Introduction To listen to events, you must implement the [`GMSMapViewDelegate`](https://developers.google.com/maps/documentation/ios-sdk/reference/objc/Protocols/GMSMapViewDelegate.md.txt) protocol. Typically, you implement this protocol on the view controller that displays the map. Below is an example: ### Swift ```swift import GoogleMaps class Events: UIViewController, GMSMapViewDelegate { // ... } ``` ### Objective-C ```objective-c @import GoogleMaps; @interface Events : UIViewController @end ```
When the `GMSMapView` is created, you can set its delegate to your view controller. The `GMSMapViewDelegate` provides only optional methods. To listen to any particular event, you must implement the relevant method. ### Swift ```swift override func loadView() { super.loadView() let camera = GMSCameraPosition.camera( withLatitude: 1.285, longitude: 103.848, zoom: 12 ) let options = GMSMapViewOptions() options.camera = camera let mapView = GMSMapView(options: options) mapView.delegate = self self.view = mapView } // MARK: GMSMapViewDelegate func mapView(_ mapView: GMSMapView, didTapAt coordinate: CLLocationCoordinate2D) { print("You tapped at \(coordinate.latitude), \(coordinate.longitude)") } ``` ### Objective-C ```objective-c - (void)loadView { [super loadView]; GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:1.285 longitude:103.848 zoom:12]; GMSMapViewOptions *options = [[GMSMapViewOptions alloc] init]; options.camera = camera; GMSMapView *mapView = [[GMSMapView alloc] initWithOptions:options]; mapView.delegate = self; self.view = mapView; } #pragma mark - GMSMapViewDelegate - (void)mapView:(GMSMapView *)mapView didTapAtCoordinate:(CLLocationCoordinate2D)coordinate { NSLog(@"You tapped at %f,%f", coordinate.latitude, coordinate.longitude); } ```
## Camera position Using the `GMSMapViewDelegate`, you can listen to changes to the camera position used to render the map. There are three distinct events. - `mapView:willMove:` indicates that the camera position is about to change. If the `gesture` argument is set to `YES`, this is due to a user performing a natural gesture on the `GMSMapView`, such as a pan or tilt. Otherwise, `NO` indicates that this is part of a programmatic change - for example, via methods such as `animateToCameraPosition:` or updating the map's layer directly. This may also be `NO` if a user has tapped on the My Location or compass buttons, which generate animations that change the camera. This method may be called several times before `mapView:idleAtCameraPosition:` is invoked, although this typically happens only if animations and gestures occur at the same time - a gesture will cancel any current animation, for instance, and will call `mapView:willMove:` a second time. - `mapView:didChangeCameraPosition:` is called repeatedly during a gesture or animation, always after a call to `mapView:willMove:`. It is passed the intermediate camera position. - Finally, `mapView:idleAtCameraPosition:` is invoked once the camera position on `GMSMapView` becomes idle, and specifies the relevant camera position. At this point, all animations and gestures have stopped. Applications can use this event to trigger a refresh of markers or other content being displayed on the `GMSMapView`, rather than, for example, reloading the content on every camera change. For example, an application can clear the `GMSMapView` on move, and then reverse geocode the position the camera comes to rest on. ### Swift ```swift let geocoder = GMSGeocoder() func mapView(_ mapView: GMSMapView, willMove gesture: Bool) { mapView.clear() } func mapView(_ mapView: GMSMapView, idleAt cameraPosition: GMSCameraPosition) { geocoder.reverseGeocodeCoordinate(cameraPosition.target) { (response, error) in guard error == nil else { return } if let result = response?.firstResult() { let marker = GMSMarker() marker.position = cameraPosition.target marker.title = result.lines?[0] marker.snippet = result.lines?[1] marker.map = mapView } } } ``` ### Objective-C ```objective-c static GMSGeocoder *geocoder; - (void)mapView:(GMSMapView *)mapView willMove:(BOOL)gesture { [mapView clear]; } - (void)mapView:(GMSMapView *)mapView idleAtCameraPosition:(GMSCameraPosition *)cameraPosition { id handler = ^(GMSReverseGeocodeResponse *response, NSError *error) { if (error != nil) { return; } GMSReverseGeocodeResult *result = response.firstResult; GMSMarker *marker = [GMSMarker markerWithPosition:cameraPosition.target]; marker.title = result.lines[0]; marker.snippet = result.lines[1]; marker.map = mapView; }; [geocoder reverseGeocodeCoordinate:cameraPosition.target completionHandler:handler]; } ```
## Events on businesses and other points of interest By default, points of interest (POIs) appear on the base map along with their corresponding icons. POIs include parks, schools, government buildings, and more, as well as business POIs such as shops, restaurants, and hotels. You can respond to click events on a POI. See the guide to [businesses and other points of interest](https://developers.google.com/maps/documentation/ios-sdk/poi.md.txt). ## Other events To learn about the full list of methods on `GMSMapViewDelegate`, see [the reference guide](https://developers.google.com/maps/documentation/ios-sdk/reference/objc/Protocols/GMSMapViewDelegate.md.txt).