MKMap object provides an embeddable map interface, similar to the one provided by the Maps application. You use this class as-is to display map information and to manipulate the map contents from your application. You can center the map on a given coordinate, specify the size of the area you want to display, and annotate the map with custom information.
- iOS 3.0+
- macOS 10.9+
- tvOS 9.2+
When you initialize a map view, you should specify the initial region for that map to display. You do this by setting the
region property of the map. A region is defined by a center point and a horizontal and vertical distance, referred to as the span. The span defines how much of the map at the given point should be visible and is also how you set the zoom level. Specifying a large span results in the user seeing a wide geographical area and corresponds to a low zoom level. Specifying a small span results in the user seeing a more narrow geographical area and corresponds to a higher zoom level.
In addition to setting the span programmatically, the
MKMap class supports many standard interactions for changing the position and zoom level of the map. In particular, map views support flick and pinch gestures for scrolling around the map and zooming in and out. Support for these gestures is enabled by default but can also be disabled using the
You can also use projected map coordinates instead of regions to specify some values. When you project the curved surface of the globe onto a flat surface, you get a two-dimensional version of a map where longitude lines appear to be parallel. To specify locations and distances, you use the
MKMap data types.
Although you should not subclass the
MKMap class itself, you can get information about the map view’s behavior by providing a delegate object. The map view calls the methods of your custom delegate to let it know about changes in the map status and to coordinate the display of custom annotations, which are described in more detail in Annotating the Map. The delegate object can be any object in your application as long as it conforms to the
MKMap protocol. For more information about implementing the delegate object, see
Annotating the Map
MKMap class supports the ability to annotate the map with custom information. Because a map may have potentially large numbers of annotations, map views differentiate between the annotation objects used to manage the annotation data and the view objects for presenting that data on the map.
An annotation object is any object that conforms to the
MKAnnotation protocol. Annotation objects are typically implemented using existing classes in your application’s data model. This allows you to manipulate the annotation data directly but still make it available to the map view. Each annotation object contains information about the annotation’s location on the map along with descriptive information that can be displayed in a callout.
The presentation of annotation objects on the screen is handled by an annotation view, which is an instance of the
MKAnnotation class. An annotation view is responsible for presenting the annotation data in a way that makes sense. For example, the Maps application uses a pin icon to denote specific points of interest on a map. (The Map Kit framework offers the
MKPin class for similar annotations in your own applications.) You could also create annotation views that cover larger portions of the map.
Because annotation views are needed only when they are onscreen, the
MKMap class provides a mechanism for queueing annotation views that are not in use. Annotation views with a reuse identifier can be detached and queued internally by the map view when they move offscreen. This feature improves memory use by keeping only a small number of annotation views in memory at once and by recycling the views you do have. It also improves scrolling performance by alleviating the need to create new views while the map is scrolling.
When configuring your map interface, you should add all of your annotation objects right away. The map view uses the coordinate data in each annotation object to determine when the corresponding annotation view needs to appear onscreen. When an annotation moves onscreen, the map view asks its delegate to create a corresponding annotation view. If your application has different types of annotations, it can define different annotation view classes to represent each type.
Adding Overlays to the Map
You can use overlays to layer content over a wide portion of the map. An overlay object is any object that conforms to the
MKOverlay protocol. An overlay object is a data object that contains the points needed to specify the shape and size of the overlay and its location on the map. Overlays can represent shapes such as circles, rectangles, multi-segment lines, and simple or complex polygons. You can also define your own custom overlays to represent other shapes.
In iOS 7 and macOS 10.9 and later, the presentation of an overlay is handled by an overlay renderer object, which is an instance of the
MKOverlay class. The job of the renderer is to draw the overlay’s content onto the screen when asked to do so by the map view. For example, if you have a simple overlay that represents a bus route, you could use a polyline renderer to draw the line segments that trace the route of the bus. You could also define a custom renderer that draws both the bus route and icons at the location of each bus stop. When specifying overlays, you can add them to specific levels of the map, which allows them to be rendered above or below other types of map content. Prior to iOS 7, overlays are drawn on onscreen using overlay views, which are instances of the
When configuring your map interface, you can add overlay objects at any time. The map view uses the data in each overlay object to determine when the corresponding overlay view needs to appear onscreen. When an overlay moves onscreen, the map view asks its delegate to create a corresponding overlay renderer.