Question

Update:Michael got it right. Here is my solution:

- (void) connectNextCarOnMainThread:(id)annotation{
    [self performSelectorOnMainThread:@selector(connectNextCar:) withObject:annotation waitUntilDone:YES];
}

- (void) connectNextCar:(id)annotation{
    Pin *pin = (Pin *)annotation;
    MKMapRect zoomRect = MKMapRectNull;
    MKMapPoint annotationPoint = MKMapPointForCoordinate(pin.coordinate);
    MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 3, 3);
    if (MKMapRectIsNull(zoomRect)) {
         zoomRect = pointRect;
    } else {
         zoomRect = MKMapRectUnion(zoomRect, pointRect);
    }
    [mapView setVisibleMapRect:zoomRect animated:YES];
    [mapView selectAnnotation:pin animated:YES];

    NSInteger currentIndex=[self.annotations indexOfObject:annotation];
    if(currentIndex < [self.annotations count]){
        [self performSelector:@selector(connectNextCarOnMainThread:) withObject:[self.annotations objectAtIndex:currentIndex+1] afterDelay:5];
    }
}

---

I want to achieve a simple feature: center and select one of my annotations every X seconds. But I’m getting some strange behavior in my annotation callouts.

Here is my code:

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated{
    if(self.movedToFitPins){
        for(id <MKAnnotation> pin in self.annotations)
            [self.mapView addAnnotation:pin];
        self.movedToFitPins = NO;
        [self performSelectorInBackground:@selector(fakeCarConnections) withObject:nil];
    }
}

- (void) fakeCarConnections {
    for (Pin *annotation in self.annotations)
    {
        [NSThread sleepForTimeInterval : 10.0];
        MKMapRect zoomRect = MKMapRectNull;
        MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);
        MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 3, 3);
        if (MKMapRectIsNull(zoomRect)) {
            zoomRect = pointRect;
        } else {
            zoomRect = MKMapRectUnion(zoomRect, pointRect);
        }
        [mapView setVisibleMapRect:zoomRect animated:YES];
        [mapView selectAnnotation:annotation animated:YES];
    }
}

So, what is happening is that I do focus on the Annotation, the callout bubble does open but with no text inside. If i click in the annotation, the callout opens up correctly with the text.
Here is the catch: if I comment the sleepForTimeInterval line, the code works fine, but I only see the last annotation since it passes trough all the others.

Answer 1

All UI modifications/messages should occur on the main thread. I’d suggest that you modify your looping code so that instead of a sleep it uses performSelectorOnMainThread after a time interval (and each subsequent call calls the next one). That way you won’t block the main thread and will still get the desired effect.