How to open callout of annotation on map automatic

问题:

I have a navigation based application for the iPhone that I am working that allows the user to view a selection from a table, on a map. I have an annotation that pinpoints the user's selected location on the map. As per normal behaviour, if the user clicks on the annotation, a callout appears with the details about the location. No problems here.

My question is, I'd like the callout to appear automatically from the annotation, once the user is taken to the screen containing the map, so that the user does not have to click on the annotation in order to see the details about the location, but I'm not sure how to do this. I have the following method in my "MapViewController" class, where the bulk of the map display work is performed:

- (void)viewDidLoad {

   [super viewDidLoad];
MKCoordinateRegion region;
MKCoordinateSpan span;

NavButtonAppDelegate *delegate = [[UIApplication sharedApplication] delegate];
userCoord = delegate.userLocation.coordinate;

region.center = userCoord; 
span.latitudeDelta = 0.4;
span.longitudeDelta = 0.4;
region.span = span;

[mapView setMapType:MKMapTypeStandard];
[mapView setZoomEnabled:YES];
[mapView setScrollEnabled:YES];
mapView.showsUserLocation = YES;
[mapView setRegion:region animated:YES]; 

RestaurantAnnotation *rAnnotation = [[RestaurantAnnotation alloc] init];
rAnnotation.title = restaurantObj.name;  
rAnnotation.subtitle = restaurantObj.address;
rAnnotation.subtitle = [restaurantObj.address stringByAppendingFormat:@" %@", restaurantObj.hours]; 
rAnnotation.subtitle = [restaurantObj.address stringByAppendingFormat:@" %@", restaurantObj.phoneNumber]; 


CLLocationCoordinate2D newCoord = {restaurantObj.latitude, restaurantObj.longitude};
rAnnotation.coordinate = newCoord;
[mapView addAnnotation:rAnnotation];

}

The MapViewController is called from the following method in the previous screen:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

Restaurant *rLocation = [restaurantList objectAtIndex:indexPath.row];

MapViewController *mapController = [[MapViewController alloc] initWithRestaurant:rLocation];
[self.navigationController pushViewController:mapController animated:YES];
[mapController release];
}

I realize that I have to use the following method to accomplish this:

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views
{
    id<MKAnnotation> myAnnotation = [mapView.annotations objectAtIndex:0];
    [mapView selectAnnotation:myAnnotation animated:YES];
}

However, I'm not sure how. I don't have many annotations that I am using all at once, I only have one annotation that I need this to work with.

Where do I put this method in my app, and where do I call it from?
Do I call this method from the viewDidLoad method and put the actual method inside my MapViewController class?

回答1:

You have to add

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views { 
    id myAnnotation = [mapView.annotations objectAtIndex:0]; 
    [mapView selectAnnotation:myAnnotation animated:YES]; 
}

to the class that you set as the delegate for the MKMapView.