How to center region in iOS6 - ios

Question

I have a problem with centering the map to a particular region. I don't know where the problem is
Map.h
#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
#interface Map : UIViewController {
MKMapView * mapView;
}
#property(nonatomic,retain) IBOutlet MKMapView * mapView;
- (IBAction)setMap:(id)sender;
- (IBAction)getLocation:(id)sender;
#end
Map.m
#import "Map.h"
#import "Annotation.h"
#interface Map ()
#end
//define coordinates
#define Sofia_LATITUDE 42.745826;
#define Sofia_LONGITUDE 23.270186;
#define Plovdiv_LATITUDE 42.1333;
#define Plovdiv_LONGITUDE 24.75;
#define Varna_LATITUDE 43.2;
#define Varna_LONGITUDE 27.9167;
#define THE_SPAN 3.8;
#implementation Map
#synthesize mapView;
- (IBAction)getLocation:(id)sender {
mapView.showsUserLocation = YES;
[self.view addSubview:mapView];
}
- (IBAction)setMap:(id)sender {
switch (((UISegmentedControl *)sender).selectedSegmentIndex) {
case 0:
mapView.mapType = MKMapTypeStandard;
break;
case 1:
mapView.mapType = MKMapTypeSatellite;
break;
case 2:
mapView.mapType = MKMapTypeHybrid;
break;
default:
break;
}
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
MKCoordinateRegion myRegion;
//Center the map
CLLocationCoordinate2D center;
center.latitude = 42.1333;
center.longitude = 24.75;
MKCoordinateSpan span;
span.latitudeDelta = THE_SPAN;
span.longitudeDelta = THE_SPAN;
myRegion.center = center;
myRegion.span = span;
[mapView setRegion:myRegion animated:TRUE];
NSMutableArray * locations = [[NSMutableArray alloc]init];
CLLocationCoordinate2D location;
Annotation * myAnn;
//make annotations
myAnn = [[Annotation alloc]init];
location.latitude = Sofia_LATITUDE;
location.longitude = Sofia_LONGITUDE;
myAnn.coordinate = location;
myAnn.title = #"Милото";
myAnn.subtitle = #"Моята любов е ТУК!!!";
[locations addObject:myAnn];
myAnn = [[Annotation alloc]init];
location.latitude = Plovdiv_LATITUDE;
location.longitude = Plovdiv_LONGITUDE;
myAnn.coordinate = location;
myAnn.title = #"Plovdiv";
myAnn.subtitle = #"Plovdiv";
[locations addObject:myAnn];
myAnn = [[Annotation alloc]init];
location.latitude = Varna_LATITUDE;
location.longitude = Varna_LONGITUDE;
myAnn.coordinate = location;
myAnn.title = #"Varna";
myAnn.subtitle = #"Varna";
[locations addObject:myAnn];
[self.mapView addAnnotations:locations];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
Annotation.h
#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>
#interface Annotation : NSObject <MKAnnotation>
#property (nonatomic, assign) CLLocationCoordinate2D coordinate;
#property (nonatomic, copy) NSString * title;
#property (nonatomic, copy) NSString * subtitle;
#end
Annotation.m
#import "Annotation.h"
#implementation Annotation
#synthesize coordinate, title, subtitle;
#end
So when I launch the program and click the button to see the map, it appears but it is not centered. When I move back and again click to see the map everything is OK. Where is the problem?

Answer 1

You need to set the region for the mapview. The region has a coordinate (the middle) and a span (the numbers of the span stand for the degrees of the world that is shown on the map), play around with the span numbers to get the result you desire. You can set the region when you set your coordinate.
MKCoordinateRegion region;
MKCoordinateSpan span;
span.latitudeDelta = 0.2;
span.longitudeDelta = 0.2;
region.span = span;
region.center = self.coordinate;
[mapView setRegion:region animated:YES];