Question

There are a few tutorials and questions on this, but I’m not knowledgeable enough yet to understand how to implement them into my particular app. I get JSON annotation data from a URL and parse it and add each annotation in for loop. I want to add a link on each annotation to open Maps for directions.

Here’s my ViewController.H

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

//MAP Setup
@interface ViewController : UIViewController <MKMapViewDelegate>

//map setup
@property (weak, nonatomic) IBOutlet MKMapView *mapView;
@property (nonatomic, strong) NSMutableData *downloadData;
//- (IBAction)refreshTapped:(id)sender;


@end

and my ViewController.m

- (void)viewDidLoad
{
    ////////////////////////
    //Connection to download JSON map info
    ////////////////////////
    self.downloadData = [NSMutableData new];

    NSURL *requestURL2 = [NSURL URLWithString:@"http:OMITTED"];
    NSURLRequest *request = [NSURLRequest requestWithURL:requestURL2];
    NSURLConnection *connection = [NSURLConnection connectionWithRequest:request delegate:self];

    //scroller
    [scroller setScrollEnabled:YES];
    [scroller setContentSize:CGSizeMake(320,900)];

    [super viewDidLoad];    

//Map
    [self.mapView.userLocation addObserver:self
                                forKeyPath:@"location"
                                   options:(NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld)
                                   context:nil];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    [self.downloadData appendData:data];

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

    id parsed = [NSJSONSerialization JSONObjectWithData:_downloadData options:kNilOptions error:nil];

    ////////////////////////
    //Iterating and adding annotations
    ////////////////////////
    for (NSDictionary *pointInfo in parsed)
    {
        NSLog([pointInfo objectForKey:@"name"]);
        double xCoord = [(NSNumber*)[pointInfo objectForKey:@"lat"] doubleValue];
        double yCoord = [(NSNumber*)[pointInfo objectForKey:@"lon"] doubleValue];
        CLLocationCoordinate2D coords = CLLocationCoordinate2DMake(xCoord, yCoord);


        MKPointAnnotation *point = [MKPointAnnotation new];
        point.coordinate = coords;
        point.title = [pointInfo objectForKey:@"name"];

        [self.mapView addAnnotation:point];// or whatever your map view's variable name is
    }
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

//centers map on user loc and then allows for movement of map without re-centering on userlocation check.
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
    if ([self.mapView showsUserLocation])
    {
        MKCoordinateRegion region;
        region.center = self.mapView.userLocation.coordinate;

        MKCoordinateSpan span;
        span.latitudeDelta  = .50; // Change these values to change the zoom
        span.longitudeDelta = .50;
        region.span = span;

        [self.mapView setRegion:region animated:YES];

        self.mapView.showsUserLocation = NO;}
}

- (void)dealloc
{
    [self.mapView.userLocation removeObserver:self forKeyPath:@"location"];
    [self.mapView removeFromSuperview]; // release crashes app
    self.mapView = nil;
}

@end

Answer 1

Launching the Maps App of the Location Awareness Programming Guide says:

If you would prefer to display map information in the Maps app as opposed to your own app, you can launch Maps programmatically using one of two techniques:

In iOS 6 and later, use an MKMapItem object to open Maps.
In iOS 5 and earlier, create and open a specially formatted map URL as described in Apple URL Scheme Reference.
The preferred way to open the Maps app is to use the MKMapItem class. This class offers both the openMapsWithItems:launchOptions: class method and the openInMapsWithLaunchOptions: instance method for opening the app and displaying locations or directions.

For an example showing how to open the Maps app, see “Asking the Maps App to Display Directions.”

So, you should:

1. Make sure to define your view controller to be the delegate for your map view;

2. Write a viewForAnnotation that turns on canShowCallout and turns on the callout accessory view:

   - (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
   {
       if ([annotation isKindOfClass:[MKUserLocation class]])
           return nil;
   
       MKAnnotationView* annotationView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation
                                                                       reuseIdentifier:@"MyCustomAnnotation"];
   
       annotationView.canShowCallout = YES;
       annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
   
       return annotationView;
   }
   

3. Then write a calloutAccessoryControlTapped method that opens the maps as outlined above, based upon what versions of iOS you’re supporting, e.g., for iOS 6:

   - (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control
   {
       id <MKAnnotation> annotation = view.annotation;
       CLLocationCoordinate2D coordinate = [annotation coordinate];
       MKPlacemark *placemark = [[MKPlacemark alloc] initWithCoordinate:coordinate addressDictionary:nil];
       MKMapItem *mapitem = [[MKMapItem alloc] initWithPlacemark:placemark];
       mapitem.name = annotation.title;
       [mapitem openInMapsWithLaunchOptions:nil];
   }
   

   I don’t know what additional geographic information your have in your KML, but you can presumably fill in the addressDictionary as you see fit.

---

In answer to your follow-up question about how to use the addressDictionary parameter of the MKPlacemark initializer method, initWithCoordinate, if you had NSString variables for the street address, the city, the state, the zip, etc., it would look like:

NSDictionary *addressDictionary = @{(NSString *)kABPersonAddressStreetKey : street,
                                    (NSString *)kABPersonAddressCityKey   : city,
                                    (NSString *)kABPersonAddressStateKey  : state,
                                    (NSString *)kABPersonAddressZIPKey    : zip};

For this to work, you have to add the appropriate framework, AddressBook.framework, to your project and import the header in your .m file:

#import <AddressBook/AddressBook.h>

The real question, though, was how to set the name for the MKMapItem so it doesn’t show up as “Unknown Location” in the maps app. That’s as simple as setting the name property, probably just grabbing the title from your annotation:

mapitem.name = annotation.title;