Working with Apple Maps on the iPhone with MapKit and the MKMapView Class

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In the preceding chapters we spent some time looking at handling raw geographical location information in the form of longitude, latitude and altitude data. The next step is to learn about the presentation of location information to the user in the form of maps and satellite images. The goal of this chapter, therefore, is provide an overview of the steps necessary to present the iPhone iOS 6 application user with location, map and satellite imagery using the MapKit framework and, in particular, the MKMapView class.




About the MapKit Framework

The MapKit Framework is based on the Apple Maps data and APIs and provides iPhone developers with a simple mechanism for integrating detailed and interactive mapping capabilities into any application.

The core element of the MapKit framework from the point of view of the app developer is the MKMapView class. This class is a subclass of UIView and provides a canvas onto which map and satellite information may be presented to the user. Information may be presented in map, satellite or hybrid (whereby the map is superimposed onto the satellite image) form. The displayed geographical region may be changed manually by the user via a process of pinching stretching and panning gestures, or programmatically from within the application code via methods calls and property manipulation on the MkMapView instance. The current location of the device may also be displayed and tracked on the map view. The MapKit framework also includes support for adding annotations to a map. This takes the form of a pin or custom image, title and subview that may be used to mark specific locations on a map.

Implementation of the MKMapViewDelegate protocol allows an application to receive notifications of events relating to the map view such as a change in either the location of the user or region of the map displayed or the failure of the device to identify the user’s current location or to download map data.

Understanding Map Regions

The area of the map that is currently displayed to the user is referred to as the region. This is defined in terms of a center location (declared by longitude and latitude) and span of the surrounding area to be displayed. Adjusting the span has the effect of zooming in and out of the map relative to the specified center location. The region’s span may be specified using either distance (in meters) or coordinate based degrees. When using degrees, one degree of latitude is equivalent to 111 km. Latitude, however, varies depending on the longitudinal distance from the equator. Given this complexity, the map view tutorial in this chapter will declare the span in terms of distance.


About the iPhone MKMapView Tutorial

The objective of this tutorial is to develop an iPhone application designed to display a map with a marker indicating the user’s current location. Buttons located in a navigation bar are provided to allow the user to zoom in on the current location and to toggle between map and satellite views. Through the implementation of the MKMapViewDelegate protocol the map will update as the user’s location changes so that the current location marker is always the center point of the displayed map region. Finally, a basic annotation will be implemented to mark a specific location on the map with a pin and title.

Creating the iPhone Map Tutorial

Begin by launching Xcode and creating a new iOS iPhone project named MapSample using the Single View Application template with Storyboards and Automatic Reference Counting enabled.

Adding the MapKit Framework to the Xcode Project

Since we will be making use of the MapKit framework during this tutorial the first step is to add the framework to the project. To achieve this, select the Build Phases tab on the MapSample summary panel and unfold the Link Binary with Libraries section. Click on the ‘+’ button, locate the MapKit.framework entry from the resulting list and click Add.

Creating the MKMapView Instance and Toolbar

The next step is to create an instance of the MKMapView class we will be using in our application and to add a toolbar instance to the user interface. Begin by selecting the MainStoryboard.storyboard and dragging a Tool Bar from the Object Library, placing it at the bottom of the view canvas. Next, drag and drop a Map View object onto the canvas and resize and position it so that it takes up the remaining space in the view above the toolbar. By default the Interface Builder tool will have added a single UIBarButtonItem to the new toolbar. For the purposes of this example, however, two buttons will be required so drag and drop a second Bar Button Item from the Object Library panel onto the toolbar. Finally, double click on the toolbar button items and change the text to “Zoom” and “Type” respectively:


<google>ADSDAQBOX_FLOW</google> Iphone ios 6 mapkit ui2.png

Figure 63-1


Select the MKMapView object in the view canvas, display the Assistant Editor panel and verify that the editor is displaying the contents of the MapSampleViewController.h file. Ctrl-click on the MKMapView object and drag to a position just below the @interface line in the Assistant Editor. Release the line and in the resulting connection dialog establish an outlet connection named mapView.

Click on the “Zoom” button to select it (note that in order to select a toolbar button item it may be necessary to click on it twice since the first click selects the toolbar parent). With the button item selected, Ctrl-click on the button object and drag the line to the area immediately beneath the newly created outlet in the Assistant Editor panel. Release the line and, within the resulting connection dialog, establish an Action method on the Touch Up Inside event configured to call a method named zoomIn. Repeat this step to connect the “Type” button to a method named changeMapType.

Select the MapSampleViewController.h file from the project navigator panel and verify that the outlets and actions have been set up correctly. Also take this opportunity to import <MapKit/MapKit.h> file and to declare the class as implementing the <MKMapViewDelegate> protocol:

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>

@interface MapSampleViewController : UIViewController
    <MKMapViewDelegate>

@property (strong, nonatomic) IBOutlet MKMapView *mapView;
- (IBAction)zoomIn:(id)sender;
- (IBAction)changeMapType:(id)sender;
@end

Perform a test run of the application’s progress so far by clicking on the Run button in the Xcode toolbar. The application should run in the iOS simulator as illustrated in Figure 63-2:


Iphone ios 6 mapview running.png

Figure 63-2

Configuring the Map View

By default the Map View does not indicate the user’s current location. By setting the showsUserLocation property of the MKMapView class the map is instructed to display a representation of the current location on the map in the form of a blue translucent ball. In order to set this property, select the MapSampleViewController.m file and locate and modify viewDidLoad: method as follows:

- (void)viewDidLoad
{
    [super viewDidLoad];
    _mapView.showsUserLocation = YES;
    
}

Changing the MapView Region

When the Zoom button is tapped by the user the map view region needs to be changed so that the user’s current location is set as the center location and the region span needs to be changed to 50 meters (analogous to zooming in to the map region). The code to implement this belongs in the zoomIn method which now needs to be implemented in the mapSampleViewController.m file:

- (IBAction)zoomIn:(id)sender {
    MKUserLocation *userLocation = _mapView.userLocation;
    MKCoordinateRegion region =
       MKCoordinateRegionMakeWithDistance (
          userLocation.location.coordinate, 50, 50);
    [_mapView setRegion:region animated:NO];
}

This method performs some very simple operations in order to achieve the desired effect in the mapView object. Firstly, the user’s current location is ascertained by accessing the userLocation property of the map view object. This is stored in the form of an MKUserLocation object which, in turn, contains the coordinates of the user. Next, the MKCoordinateRegionMakeWithDistance function is called in order to generate an MKCoordinateRegion object consisting of the user’s location coordinates and a span that stretches 50 meters both to the North and South of the current location. Finally, this region object is passed through to the setRegion method of the mapView object.

Now that the Zoom functionality has been implemented it is time to configure the map type switching feature of the application.

Changing the Map Type

The map type of a map view is controlled by the object’s mapType property. Supported values for this property are MKMapTypeStandard, MKMapTypeSatellite and MKMapTypeHybrid. For the purposes of this example application the map will switch between standard and satellite modes. Within the MapSampleViewController.m file modify the changeMapType action method connected to the Type button as follows:

- (IBAction)changeMapType:(id)sender {
    if (_mapView.mapType == MKMapTypeStandard)
        _mapView.mapType = MKMapTypeSatellite;
    else
        _mapView.mapType = MKMapTypeStandard;
} 

This very simple method simply toggles between the two map types when the button is tapped by the user.

Testing the iPhone MapView Application

Now that more functionality has been implemented, it is a good time to build and run the application again so click on the Xcode Run button to load the application into the iOS iPhone Simulator. Once the application has loaded, a blue dot should appear over Northern California. Since the application is running in the simulator environment the location information is simulated to match the coordinates of Apple’s headquarters in Cupertino, CA. Select the Type button to display the satellite view and then zoom in to get a better look at the company’s buildings:


Iphone ios 6 mapview apple.png

Figure 63-3


To get real location information, load the application onto an iPhone device (details of which can be found in the Testing iOS 6 Apps on the iPhone – Developer Certificates and Provisioning Profiles chapter of this book).

Updating the Map View based on User Movement

Assuming that you installed the application on a physical iPhone device and went somewhere with the device in your possession you may have noticed that the map did not update as your location changed and that the blue dot marking your current location eventually went off the screen (also assuming, of course, that you had zoomed in).

In order to configure the application so that the map automatically tracks the movements of the user, the first step is to make sure the application is notified when the location changes. At the start of this tutorial the view controller was declared as conforming to the MKMapViewDelegate delegate protocol. One of the methods that comprise this protocol is the didUpdateUserLocation method. When implemented, this method is called by the map view object whenever the location of the device changes. We must, therefore, first specify that the MapSampleViewContoller class is the delegate for the mapView object, which can be performed by adding the following line to the viewDidLoad method located in the MapSampleViewController.m file:

_mapView.delegate = self; 

The next task involves the implementation of the didUpdateUserLocation method in the MapSampleViewController.m file:

- (void)mapView:(MKMapView *)mapView 
didUpdateUserLocation:
(MKUserLocation *)userLocation
{
    _mapView.centerCoordinate = 
          userLocation.location.coordinate;
} 

The delegate method is passed as an argument an MKUserLocation object containing the current location coordinates of the user. This value is simply assigned to the center coordinate property of the mapView object such that the current location remains at the center of the region. When the application is now installed and run on a device the current location will no longer move outside the displayed region as the device location changes. To experience this effect within the simulator, simply select the Debug -> Location -> City Run menu option and then select the Zoom button in the user interface.

Adding Basic Annotations to a Map View

The last task in this tutorial is to add an annotation at a specific location on the map view. For the purposes of this example, we will add a standard annotation (represented by default by a red pin) at the coordinates of Microsoft’s headquarters in Redmond, Washington. Although this is a very simple example it is important to keep in mind that annotations may also be used to perform more advanced tasks such as displaying custom images and multiple annotations on a single map.

The annotation in this example will also display a title and subtitle when selected by the user. In order to create a basic annotation it is necessary to create a CLLocationCoordinate2D object containing the coordinates at which the annotation is to appear. An MKPointAnnotation object is then created and assigned the coordinate object, title and subtitle strings. Finally the addAnnotation method of the map view object is called to add the annotation to the map. The code fragment for these steps is as follows:

CLLocationCoordinate2D annotationCoord;

annotationCoord.latitude = 47.640071;
annotationCoord.longitude = -122.129598;

MKPointAnnotation *annotationPoint = [[MKPointAnnotation alloc] init];
annotationPoint.coordinate = annotationCoord;
annotationPoint.title = @"Microsoft";
annotationPoint.subtitle = @"Microsoft's headquarters";
[_mapView addAnnotation:annotationPoint]; 

Add this code to the end of the viewDidLoad method and build and run the application. The map should now appear with a red pin located at the designated location. Tapping the pin will display the title and subtitle:


Iphone ios 6 mapkit annotation.png

Figure 63-4


Purchase the fully updated iOS 10 / Swift 3 / Xcode 8 edition of this book in eBook ($19.99) or Print ($45.99) format.
iOS 10 App Development Essentials Print and eBook (ePub/PDF/Kindle) edition contains over 100 chapters. Learn more...

Buy eBook Buy Print Preview Book



PreviousTable of ContentsNext
An Example iOS 6 iPhone Location ApplicationUsing iOS 6 Event Kit to Create Date and Location Based Reminders