Set the correct zoom in a MKMapView - iphone

Question

I made a count-steps app, I count the steps with the iPhone accelerometer and now I want to display the path I made on a mapView. I can easily show the map and catch the right position with the iPhone GPS, I can display the start and the end point and I can to draw a polyline to show the path I made. Now my problem is how to set a correct zoom on the map? When I open the ViewController with map the zoom it's too far and I've to zoom to see the path I made.
So my question is how to set a correct zoom?
I post here the code of the View Controller with the mapView:
ResultViewController.m
#import "ResultViewController.h"
#import "MapAnnotation.h"
#interface ResultViewController ()
#property (nonatomic, strong)NSMutableArray *mapAnnotation;
#property (nonatomic) BOOL needUpdateRegion;
#end
#implementation ResultViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.labelResult.text = self.totalSteps;
[self.mapView setDelegate:self];
self.needUpdateRegion = YES;
self.mapAnnotation = [[NSMutableArray alloc]initWithCapacity:2];
CLLocation *startLocation = [self.locationArray objectAtIndex:0];
CLLocation *stopLocation = [self.locationArray lastObject];
NSString *startLatitude = [NSString stringWithFormat:#"%f", startLocation.coordinate.latitude];
NSString *startLongitude = [NSString stringWithFormat:#"%f", startLocation.coordinate.longitude];
NSString *stopLatitude = [NSString stringWithFormat:#"%f", stopLocation.coordinate.latitude];
NSString *stopLongitude = [NSString stringWithFormat:#"%f", stopLocation.coordinate.longitude];
MapAnnotation *startPlace = [[MapAnnotation alloc]initWithCoordinate:startLatitude andLong:startLongitude];
MapAnnotation *stopPlace = [[MapAnnotation alloc]initWithCoordinate:stopLatitude andLong:stopLongitude];
[self.mapAnnotation insertObject:startPlace atIndex:0];
[self.mapAnnotation insertObject:stopPlace atIndex:1];
if (self.mapAnnotation) {
[self.mapView removeAnnotations:self.mapView.annotations];
}
[self.mapView addAnnotation:self.mapAnnotation[0]];
[self.mapView addAnnotation:self.mapAnnotation[1]];
[self updateRegion];
[self createMKpolylineAnnotation];
}
- (void)updateRegion
{
self.needUpdateRegion = NO;
CGRect boundingRect;
BOOL started = NO;
for (id <MKAnnotation> annotation in self.mapView.annotations) {
CGRect annotationRect = CGRectMake(annotation.coordinate.latitude, annotation.coordinate.longitude, 0, 0);
if (!started) {
started = YES;
boundingRect = annotationRect;
} else {
boundingRect = CGRectUnion(boundingRect, annotationRect);
}
}
if (started) {
boundingRect = CGRectInset(boundingRect, -0.2, -0.2);
if ((boundingRect.size.width < 20) && (boundingRect.size.height < 20)) {
MKCoordinateRegion region;
region.center.latitude = boundingRect.origin.x + boundingRect.size.width / 2;
region.center.longitude = boundingRect.origin.y + boundingRect.size.height / 2;
region.span.latitudeDelta = boundingRect.size.width;
region.span.longitudeDelta = boundingRect.size.height;
[self.mapView setRegion:region animated:YES];
}
}
}
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay {
MKPolylineView *polylineView = [[MKPolylineView alloc] initWithPolyline:overlay];
polylineView.strokeColor = [UIColor blueColor];
polylineView.lineWidth = 5.0;
return polylineView;
}
- (void)createMKpolylineAnnotation {
NSInteger numberOfSteps = self.locationArray.count;
CLLocationCoordinate2D *coords = malloc(sizeof(CLLocationCoordinate2D) * numberOfSteps);
for (NSInteger index = 0; index < numberOfSteps; index++) {
CLLocation *location = [self.locationArray objectAtIndex:index];
CLLocationCoordinate2D coordinate = location.coordinate;
coords[index] = coordinate;
}
MKPolyline *polyLine = [MKPolyline polylineWithCoordinates:coords count:numberOfSteps];
[self.mapView addOverlay:polyLine];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)restart:(id)sender {
[self dismissViewControllerAnimated:YES completion:nil];
}
#end
What's wrong with this code? There's someone that can help me to zoom the map correctly?
Thank you

Answer 1

In that case I would recommend you to call the following method in order to zoom to a region of the map, you could add the call at the end your method - (void)createMKpolylineAnnotation;
Call:
[self zoomToPolyLine: self.mapView polyLine:polyLine animated:YES];
Method:
-(void)zoomToPolyLine:(MKMapView*)map polyLine:(MKPolyline*)polyLine
animated:(BOOL)animated
{
MKPolygon* polygon = [MKPolygon polygonWithPoints:polyLine.points count:polyLine.pointCount];
[map setRegion:MKCoordinateRegionForMapRect([polygon boundingMapRect])
animated:animated];
}

Answer 2

firstly add this line in view did load after you set the mapview delegate as
[self.mapView setDelegate:self];
self.needUpdateRegion = YES;
mapView.zoomEnabled = YES;
mapView.scrollEnabled = YES;
....
}
then modify the below line to set the zoom level as required by you 60000=60 km..
[mapView setRegion: MKCoordinateRegionMakeWithDistance(site.coordinate, 60000, 60000) animated:YES];
or you can try this method for setting scale of zoom as
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {
CGImageRef imageReference = self.overlayImage.CGImage;
MKMapRect theMapRect = self.overlay.boundingMapRect;
CGRect theRect = [self rectForMapRect:theMapRect];
CGContextScaleCTM(context, 1.0, -1.0);
CGContextTranslateCTM(context, 0.0, -theRect.size.height);
CGContextDrawImage(context, theRect, imageReference);
}
hope this helps you..Cheers!!