iOS SDK Mapview Annotation callout redraw error

Question

I'm trying to add the distance from the user's position to a selected annotation's subtitle in a mapview. The mechanics of it are working, but the actual callout gets messed up the first time it's displayed. There appears to be a redraw problem.

mapView annotation redraw problem

Subsequent taps on the pin show the correct layout.

Here's the relevant code:

// called when selecting annotations

- (void)mapView:(MKMapView *)mapView didSelectAnnotationView:(MKAnnotationView *)view{

MKPointAnnotation *selectedAnnotation = view.annotation;

//attempt to add distance on annotation
CLLocation *pointALocation = [[CLLocation alloc] 
                              initWithLatitude:selectedAnnotation.coordinate.latitude 
                              longitude:selectedAnnotation.coordinate.longitude];
float distanceMeters = [pointALocation distanceFromLocation:locationManager.location];

//for sending info to detail
myPinTitle = selectedAnnotation.title;

[selectedAnnotation setSubtitle:[NSString stringWithFormat:@"%.2f miles away", (distanceMeters / 1609.344)]];

} I've tried calling [view setNeedsDisplay], but to no avail.

Thanks in advance for your help.

The Solution that Worked

Here's the solution I finally came up with. It seems to work.

I edited out the duplicate code from the didSelectAnnotationView method, above, and came up with:

//called when user location changes

- (void)updatePinsDistance
{
for (int x=0; x< [[mapView annotations]count]; x++) {
    MKPointAnnotation *thisPin =[[mapView annotations] objectAtIndex:x];

    //attempt to add distance on annotation
    CLLocation *pointALocation = [[CLLocation alloc] 
                                 initWithLatitude:thisPin.coordinate.latitude 
                                 longitude:thisPin.coordinate.longitude];
    float distanceMeters = [pointALocation distanceFromLocation:locationManager.location];
    NSString *distanceMiles = [NSString stringWithFormat:@"%.2f miles from you",
                                                    (distanceMeters / 1609.344)];

    [thisPin setSubtitle:distanceMiles];
    }
}

Cyril Godefroy Cyril Godefroy · Accepted Answer · 2012-04-09T17:03:54

You should set your subtitle in another place than didSelectAnnotationView. Actually all annotationViews should have their title and subtitle set before they are returned by the mapView:viewForAnnotation: method.

The fact that you set a long subtitle certainly explains that the callout is not the right size. The size must be calculated before the didSelectAnnotationView is called.

iOS SDK Mapview Annotation callout redraw error

The Solution that Worked

1 Answers