Refresh MKAnnotationView on a MKMapView

Question

I'd like to a-synchronically load images for my custom MKAnnotationView; I'm already using the EGOImageView-framework (it goes very well with UITableViews), but I fail to make it work on MKMapView. Images seem to be loaded, but I cannot refresh them on the map - [myMap setNeedsDisplay] does nothing.

Answer 1

I haven't tried it myself, but it might work:
Get a view for annotation using MKMapView - (MKAnnotationView *)viewForAnnotation:(id <MKAnnotation>)annotation method and set new image to it.

Edit: Tried to do that myself and this approach worked fine for me:

//  Function where you got new image and want to set it to annotation view
for (MyAnnotationType* myAnnot in myAnnotationContainer){
    MKAnnotationView* aView = [mapView viewForAnnotation: myAnnot];
    aView.image = [UIImage imageNamed:@"myJustDownloadedImage.png"];
}

After calling this method all annotations images were updated.

Answer 2

I found only one reliable way to update annotation, others methods didn't work for me: just removing and adding annotation again:

id <MKAnnotation> annotation;

// ...

[mapView removeAnnotation:annotation];
[mapView addAnnotation:annotation];

This code will make -[mapView:viewForAnnotation:] to be called again and so your annotation view will be created again (or maybe reused if you use dequeueReusableAnnotationViewWithIdentifier) with correct data.

Answer 3

This is the only way I've found to force redraw of MKAnnotationViews:

// force update of map view (otherwise annotation views won't redraw)

CLLocationCoordinate2D center = mapView.centerCoordinate;

mapView.centerCoordinate = center;

Seems useless, but it works.

Answer 4

This worked for me

#import "EGOImageView.h"

- (MKAnnotationView *)mapView:(MKMapView *)theMapView viewForAnnotation:(id <MKAnnotation>)annotation
{
    //ENTER_METHOD;    
    if([annotation isKindOfClass:[MKUserLocation class]]) return nil;  
    MKPinAnnotationView *annView;

    static NSString *reuseIdentifier = @"reusedAnnView";
    annView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:reuseIdentifier];
    annView.canShowCallout = YES;
    annView.calloutOffset = CGPointMake(-5.0f, 0.0f);
    annView.opaque = NO;
    annView.image = [[UIImage imageNamed:@"tempImage.png"] retain];

    YourModel *p = annotation; // make this conform to <MKAnnotation>
    EGOImageView *egoIV = [[EGOImageView alloc] initWithPlaceholderImage:[UIImage imageNamed:@"tempImage.png"]];
    [egoIV setDelegate:self];
    egoIV.imageURL = [NSURL URLWithString:p.theUrlToDownloadFrom];
    [annView addSubview:egoIV];
    [egoIV release];


    return [annView autorelease];
}

Answer 5

Thank you @Vladimir for the help! Your answer inspired my answer. I made some changes to make it clearer.

func addAnnotation(coordinate: CLLocationCoordinate2D) {
    let annotation = Annotation()
    annotation.coordinate = coordinate
    annotations.append(annotation)
    mapView.addAnnotation(annotation)
    for index in 0..<annotations.count {
        if let view = mapView.view(for: annotations[index]) as? AnnotationView {
            if index == 0 {
                view.imageView.image = NSImage(named: "icon_positioning")
            } else {
                view.imageView.image = NSImage(named: "icon_positioning")
            }
        }
    }
}

Also the protocol in MKMapview needs to implement:

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    let view = mapView.dequeueReusable(withClass: AnnotationView.self, annotation: annotation)
    if index == 0 {
        view.imageView.image = NSImage(named: "icon_positioning")
    } else {
        view.imageView.image = NSImage(named: "icon_positioning")
    }
    return view
}

By the way, the AnnotationView initialization here is:

public extension MKMapView {
    func dequeueReusable<T: MKAnnotationView>(withClass name: T.Type,annotation: MKAnnotation?) -> T {
        if let view = dequeueReusableAnnotationView(withIdentifier: T.identifier()) as? T {
            return view
        }
        let view = T.init(annotation: annotation, reuseIdentifier: T.identifier())
        return view
    }
}

Thanks again @Vladimir for the answer

Answer 6

(I don't see how to indicate that this post pertains to zerodiv's answer.) I was able to get zerodiv's method to work by adding a kickstart of sorts, forcing a meaningless but different coordinate, then restoring the prior, correct one. The screen doesn't flash at all because of the first location.

CLLocationCoordinate2D center = mapView.centerCoordinate; 
CLLocationCoordinate2D forceChg;
forceChg.latitude = 0;
forceChg.longitude = curLongNum;

mapView.centerCoordinate = forceChg;
mapView.centerCoordinate = center;

Answer 7

I wanted to refresh user location pin with new selected avatar. I found another fast solution for that case. I have 2 screens. The first one is for selecting avatar and the second is for displaying user on map.

swift 5 You can change user location image by creating MKAnnotationView

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {

    if annotation is MKUserLocation {
        let userIdentifier = "UserLocation"
        var userView = mapView.dequeueReusableAnnotationView(withIdentifier: userIdentifier)
        if userView == nil {
            userView = MKAnnotationView(annotation: annotation, reuseIdentifier: userIdentifier)
        } else {
            userView?.annotation = annotation
        }

        userView!.image = UIImage(named: "avatar1") //your image

        return userView
    }

    return nil
 }

So if user will change avatar to something else, for example to "avatar2" it won't refresh.

In order to refresh user location image i added this code in viewWillAppear()

 self.mapView.showsUserLocation = false
 self.mapView.showsUserLocation = true