Zoom to random annotation and show bubble when map view loads - ios

Question

I am trying to zoom to a random annotation AND have the bubble open automatically as well.
I am pinning my annotations in the viewDidLoad as follows:
...arrays...
for (int i=0; i<22; i++){
MKPointAnnotation *annot = [[MKPointAnnotation alloc] init];
annot.title = [wineryName objectAtIndex:i];
annot.subtitle = [wineryAddress objectAtIndex:i];
annot.coordinate = CLLocationCoordinate2DMake([[lat objectAtIndex:i]doubleValue], [[lon objectAtIndex:i]doubleValue]);
[mapView setCenterCoordinate:annot.coordinate animated:YES];
[mapView addAnnotation:annot];
then I am styling the bubble as follows:
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
if ([annotation isKindOfClass:[MKUserLocation class]])
return nil;
//dequeue an existing pin view first
static NSString* AnnotationIdentifier = #"AnnotationIdentifier";
MKPinAnnotationView* pinView = [[[MKPinAnnotationView alloc]
initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier] autorelease];
pinView.animatesDrop=YES;
pinView.canShowCallout=YES;
pinView.pinColor=MKPinAnnotationColorRed;
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
button.frame = CGRectMake(0, 0, 35, 35);
button.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
button.contentHorizontalAlignment = UIControlContentHorizontalAlignmentCenter;
[button setImage:[UIImage imageNamed:#"RightArrow.png"] forState:UIControlStateNormal];
[button addTarget:self action:#selector(showDetails:) forControlEvents:UIControlEventTouchUpInside];
pinView.rightCalloutAccessoryView = button;
...arrays...
for (int i = 0; i < 22; i++) {
if ([wineryTitle[i] isEqualToString:[annotation title]]) {
UIImageView *profileIconView = [[UIImageView alloc] init];
profileIconView.frame = CGRectMake(0, 0, 40, 33);
profileIconView.image = [UIImage imageNamed:wineryImage[i]];
pinView.leftCalloutAccessoryView = profileIconView;
[profileIconView release];
break;
}
}
return pinView;
}
then I am trying to zoom to a random location as follows:
- (void)zoomToUserLocation:(MKUserLocation *)userLocation
{
if (!userLocation)
return;
MKCoordinateRegion region;
//zoom to random pin when page loads
int randomNumber = rand() % 22;
switch (randomNumber) {
case 1:
region.center = CLLocationCoordinate2DMake(34.642109, -120.440292);
[self.mapView selectAnnotation:[self.mapView.annotations objectAtIndex:0] animated:TRUE];
break;
case 2:
region.center = CLLocationCoordinate2DMake(34.667408, -120.334781);
[self.mapView selectAnnotation:[self.mapView.annotations objectAtIndex:1] animated:TRUE];
break;
case 3:
...etc
}
region.span = MKCoordinateSpanMake(5.0, 5.0);
region = [self.mapView regionThatFits:region];
[self.mapView setRegion:region animated:YES];
}
ALL OF THIS WORKS< EXCEPT: In the zoomToUserLocation method, the map is zooming to one location and then showing the bubble of a different location. It seems like the random operator is randomly selecting a location and a bubble separately. Does anyone know how to fix this so that the bubble automatically appears at the same location that is randomly selected?

Answer 1

The code in the zoomToUserLocation method is making the wrong assumption that the map view's annotations array only contains the annotations you explicitly added and (more importantly) that the annotations array will be in the same order that you added the annotations in.
Both of those assumptions are unsafe to make.
For some more discussion, see MKMapView annotations changing/losing order?.
Your app is apparently adding 22 annotations but:
If showsUserLocation is YES, then the map view's annotations array will contain 23 annotations (your 22 and the user location that the map adds itself).
There is no guarantee that the annotation at index N of the map's annotations array will be the same annotation that is at index N in your winery array.
For your purpose of simply zooming to a random location, it is not really necessary to establish a link between the map's annotations array and your own array(s).
Instead, the coordinates to center on can be retrieved from the randomly chosen annotation from the annotations array itself.
For example:
MKCoordinateRegion region;
//make list of annotations excluding the user location
NSMutableArray *myAnnotations = [NSMutableArray arrayWithCapacity:10];
for (id<MKAnnotation> ann in self.mapView.annotations)
{
if (! ([ann isKindOfClass:[MKUserLocation class]]))
[myAnnotations addObject:ann];
}
int numOfAnnotations = myAnnotations.count;
//if no annotations to choose from, do nothing
if (numOfAnnotations == 0)
return;
int randomNumber = rand() % numOfAnnotations;
//suggest using arc4random instead of rand
//see https://stackoverflow.com/questions/160890/generating-random-numbers-in-objective-c
id<MKAnnotation> randomAnnotation = [myAnnotations objectAtIndex:randomNumber];
region.center = randomAnnotation.coordinate;
[self.mapView selectAnnotation:randomAnnotation animated:YES];
region.span = ... //rest of the code as-is
//however, calling regionThatFits is unnecessary
There are numerous other unrelated improvements that could be made to the code but those will have to be the topic of separate questions. Here are a couple of them however...
One major improvement I can suggest is to create a custom annotation class (called Winery perhaps) which consolidates all the data of a winery into a single object rather than using separate arrays for the name, address, latitude, longitude, image, etc.
This will make development and future changes much easier to manage.
The second major improvement is to remove the inefficient loop in the viewForAnnotation delegate method which searches for the winery name in order to set the left accessory view's image. This search loop is executed every time the annotation view is needed. With just 22 annotations, you may not notice a performance issue but it's unnecessary work. If the first improvement is done, the search loop can be eliminated since all the annotation's properties will already be in the annotation object.
See Optimizing Code for MKMapView - Large Number of Annotations for some idea of the above.