How to make custom MKAnnotation draggable

Question

I need MKAnnotation with different pin image.
So I created following:

@interface NavigationAnnotation : NSObject <MKAnnotation>
- (id)initWithName:(NSString*)name address:(NSString*)address coordinate:(CLLocationCoordinate2D)coordinate;
...
@interface NavigationAnnotation ()
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *address;
@property (nonatomic, assign) CLLocationCoordinate2D theCoordinate;
@end

@implementation NavigationAnnotation


- (id)initWithName:(NSString*)name address:(NSString*)address coordinate:(CLLocationCoordinate2D)coordinate {
    if ((self = [super init])) {
        if ([name isKindOfClass:[NSString class]]) {
            self.name = name;
        } else {
            self.name = @"Unknown charge";
        }
        self.address = address;
        self.theCoordinate = coordinate;
    }
    return self;
}

- (NSString *)title {
    return _name;
}

- (NSString *)subtitle {
    return _address;
}

- (CLLocationCoordinate2D)coordinate {
    return _theCoordinate;
}

And add it like this:

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation{

    static NSString *identifier_OrderAnnotation = @"NavigateAnnotation";

    if ([annotation isKindOfClass:[MKUserLocation class]])
        return nil;

    if ([annotation isKindOfClass:[NavigationAnnotation class]]) {

        MKAnnotationView *annotationView = (MKAnnotationView *) [_mapView dequeueReusableAnnotationViewWithIdentifier:identifier_OrderAnnotation];
        if (annotationView == nil) {
            annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier_OrderAnnotation];
            annotationView.enabled = YES;
            annotationView.canShowCallout = YES;
            annotationView.draggable = YES;
            annotationView.image = [UIImage imageNamed:@"myimage.png"];
        } else {
            annotationView.annotation = annotation;
        }

        return annotationView;
    }
}

Annotation shows on map fine but it is not draggable from some reason :(

Answer 1

As already mentioned, for an annotation to be draggable, it must implement a setCoordinate: method.

Additionally, since iOS 7, you may also need to implement the mapView:annotationView:didChangeDragState: method (see Draggable Pin does not have a fixed position on map and iOS MapKit dragged annotations (MKAnnotationView) no longer pan with map).

You can either implement the setCoordinate: method explicitly yourself or just declare a writeable coordinate property (named exactly like that) and synthesize it (and the getter and setter methods will be automatically implemented for you).

(Note that if you use the pre-defined MKPointAnnotation class, you don't need to do this because that class already implements a settable coordinate property.)

In your NavigationAnnotation class, to implement the explicit, manual solution to work with the existing theCoordinate property, just add the setCoordinate: method to your class implementation (keep the existing getter method):

-(void)setCoordinate:(CLLocationCoordinate2D)newCoordinate
{
    self.theCoordinate = newCoordinate;
}

You may also need to implement the didChangeDragState: method in the class that implements the map view delegate (the same one that has the viewForAnnotation method) otherwise after dragging, the annotation view will hover in-place above the map even while it is panned or zoomed underneath. An example implementation of the method as given by Chris K. in his answer:

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)annotationView didChangeDragState:(MKAnnotationViewDragState)newState fromOldState:(MKAnnotationViewDragState)oldState
{
    if (newState == MKAnnotationViewDragStateStarting)
    {
        annotationView.dragState = MKAnnotationViewDragStateDragging;
    }
    else if (newState == MKAnnotationViewDragStateEnding || newState == MKAnnotationViewDragStateCanceling)
    {
        annotationView.dragState = MKAnnotationViewDragStateNone;
    }
}

Answer 2

Just went through this issue... After some struggling, reason was different (title, coordinate were ok), so adding possible cause here

In my annotation view, I did override - (void) setSelected:(BOOL)selected

Without calling [super setSelected:selected]; This prevented the dragging from occuring...