Drag an annotation pin on a mapview

Question

The annotation pin is draggable but I couldn't drop it to the destination location. The problem is how could I get the destination location's coordinate where i drop the annotation pin? Any method exist?

Edit 1:

The center of the annotation pin seems never changed where ever I drop the pin.

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)annotationView didChangeDragState:(MKAnnotationViewDragState)newState 
fromOldState:(MKAnnotationViewDragState)oldState 
{
if (newState == MKAnnotationViewDragStateEnding)
{
    NSLog(@"x is %f", annotationView.center.x);
    NSLog(@"y is %f", annotationView.center.y);

    CGPoint dropPoint = CGPointMake(annotationView.center.x, annotationView.center.y);
    CLLocationCoordinate2D newCoordinate = [self.mapView convertPoint:dropPoint toCoordinateFromView:annotationView.superview];
    [annotationView.annotation setCoordinate:newCoordinate];

}
}

Edit 2:

Annotation.h

@property (nonatomic,readwrite,assign) CLLocationCoordinate2D coordinate;

Annotation.m

- (void)setCoordinate:(CLLocationCoordinate2D)newCoordinate {
coordinate = newCoordinate; 
}

Edit 3: where ever I drag the pin, the NSLog out put of the droppedAt is always the same.

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)annotationView didChangeDragState:(MKAnnotationViewDragState)newState 
fromOldState:(MKAnnotationViewDragState)oldState 
{
if (newState == MKAnnotationViewDragStateEnding)
{
    CLLocationCoordinate2D droppedAt = annotationView.annotation.coordinate;
    NSLog(@"Pin dropped at %f,%f", droppedAt.latitude, droppedAt.longitude);
}
}

Edit 4:

Annotaion.m @dynamic startAddr;

- (CLLocationCoordinate2D)coordinate
{
coordinate.latitude = [self.startAddr.latitude doubleValue];
coordinate.longitude = [self.startAddr.longitude doubleValue];    
return coordinate;
}

- (void)setCoordinate:(CLLocationCoordinate2D)newCoordinate {
//I need to update the self.startAddr.latitude and longitude here. Problem solved.
self.startAddr.latitude = [NSNumber numberWithDouble:newCoordinate.latitude];
self.startAddr.longitude = [NSNumber numberWithDouble:newCoordinate.longitude];

coordinate = newCoordinate; 
}

Answer 1

First you have to create a custom annotation like this:

MyAnnotation.h

#import <MapKit/MapKit.h>

@interface MyAnnotation : NSObject <MKAnnotation>{

    CLLocationCoordinate2D coordinate;

}
- (id)initWithCoordinate:(CLLocationCoordinate2D)coord;
- (void)setCoordinate:(CLLocationCoordinate2D)newCoordinate;
@end

MyAnnotation.m

#import "MyAnnotation.h"

@implementation MyAnnotation
@synthesize coordinate;

- (NSString *)subtitle{
    return nil;
}

- (NSString *)title{
    return nil;
}

-(id)initWithCoordinate:(CLLocationCoordinate2D)coord {
    coordinate=coord;
    return self;
}

-(CLLocationCoordinate2D)coord
{
    return coordinate;
}

- (void)setCoordinate:(CLLocationCoordinate2D)newCoordinate {
    coordinate = newCoordinate; 
}

@end

After that, you just have to use your annotation like this:

// Assuming you have imported MyAnnotation.h and you have a self.map property pointing to a MKMapView
MyAnnotation *myPin = [[MyAnnotation alloc] initWithCoordinate:self.map.centerCoordinate]; // Or whatever coordinates...
[self.map addAnnotation:myPin];

Also, you have to return a view for your annotation. You can do so like this:

- (MKAnnotationView *) mapView: (MKMapView *) mapView viewForAnnotation: (id<MKAnnotation>) annotation {
    MKPinAnnotationView *pin = (MKPinAnnotationView *) [self.map dequeueReusableAnnotationViewWithIdentifier: @"myPin"];
    if (pin == nil) {
        pin = [[[MKPinAnnotationView alloc] initWithAnnotation: annotation reuseIdentifier: @"myPin"] autorelease]; // If you use ARC, take out 'autorelease'
    } else {
        pin.annotation = annotation;
    }
    pin.animatesDrop = YES;
    pin.draggable = YES;

    return pin;
}

Then, once you have adopted the MKMapViewDelegate protocol in your controller, you grab the coordinates of a pin after dragging it like this:

- (void)mapView:(MKMapView *)mapView 
 annotationView:(MKAnnotationView *)annotationView 
didChangeDragState:(MKAnnotationViewDragState)newState 
   fromOldState:(MKAnnotationViewDragState)oldState 
{
    if (newState == MKAnnotationViewDragStateEnding)
    {
        CLLocationCoordinate2D droppedAt = annotationView.annotation.coordinate;
        NSLog(@"Pin dropped at %f,%f", droppedAt.latitude, droppedAt.longitude);
    }
}

Answer 2

Out of the blue, implement the setCoordinates method of your annotation and make a callBAck when your annotation coordinates have changed

edit : beware of the dragState property of your annotation while its moving.

Answer 3

Don't you wan't to do this :

Setting the annotation delegate, then

- (void)setCoordinate:(CLLocationCoordinate2D)newCoordinate {
   coordinate = newCoordinate; 
   if (self.delegate respondsToSelector:@selector(mapAnnotationCoordinateHaveChanged))
    [self.delegate performSelector(@selector(mapAnnotationCoordinateHaveChanged))];
}

In your delegate :

- (void) mapAnnotationCoordinateHaveChanged{
 //some coordinates update code
}

Answer 4

- (MKAnnotationView *) mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>) annotation
{
    MKAnnotationView *a = [ [ MKAnnotationView alloc ] initWithAnnotation:annotation reuseIdentifier:@"currentloc"];
    //  a.title = @"test";
    if ( a == nil )
        a = [ [ MKAnnotationView alloc ] initWithAnnotation:annotation reuseIdentifier: @"currentloc" ];

    NSLog(@"%f",a.annotation.coordinate.latitude);
    NSLog(@"%f",a.annotation.coordinate.longitude);

    CLLocation* currentLocationMap = [[[CLLocation alloc] initWithLatitude:a.annotation.coordinate.latitude longitude:a.annotation.coordinate.longitude] autorelease];
    [self coordinatesToDMS:currentLocationMap];


    MKPinAnnotationView *annView=[[MKPinAnnotationView alloc] initWithAnnotation:a reuseIdentifier:@"currentloc"];
    if(a.annotation.coordinate.longitude == mapView.userLocation.coordinate.longitude ||  a.annotation.coordinate.latitude == mapView.userLocation.coordinate.latitude  )
    {
        if ([annotation isKindOfClass:MKUserLocation.class])
        {
            //user location view is being requested,
            //return nil so it uses the default which is a blue dot...
            return nil;
        }       
        //a.image = [UIImage imageNamed:@"userlocation.png"];
        //a.pinColor=[UIColor redColor];
    }
    else 
    {

        // annView.image =[UIImage imageNamed:@"map-pin.png"];
        //PinFirst=FALSE;
        //annView.pinColor = [UIColor redColor];
        // annView.annotation=annotation;
    }

    annView.animatesDrop = YES;
    annView.draggable = YES;

    annView.canShowCallout = YES;

    return annView;
}

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated
{
    NSLog(@"map Drag");
}

- (void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view didChangeDragState:(MKAnnotationViewDragState)newState
fromOldState:(MKAnnotationViewDragState)oldState;
{
    NSLog(@"pin Drag");

    if (newState == MKAnnotationViewDragStateEnding)
    {
        CLLocationCoordinate2D droppedAt = view.annotation.coordinate;
        NSLog(@"Pin dropped at %f,%f", droppedAt.latitude, droppedAt.longitude);

        CLLocation* draglocation = [[[CLLocation alloc] initWithLatitude:droppedAt.latitude longitude:droppedAt.longitude] autorelease];



    }
}

Answer 5

Example for Swift 2.2, Xcode 7.3.1:

• Create custom class adopting MKAnnotation protocol

  (note: Swift doesn't have automatic notification for KVO-compliant properties, so I have added my own - this is not required):

   import MapKit class MyAnnotation: NSObject, MKAnnotation { // MARK: - Required KVO-compliant Property var coordinate: CLLocationCoordinate2D { willSet(newCoordinate) { let notification = NSNotification(name: "VTAnnotationWillSet", object: nil) NSNotificationCenter.defaultCenter().postNotification(notification) } didSet { let notification = NSNotification(name: "VTAnnotationDidSet", object: nil) NSNotificationCenter.defaultCenter().postNotification(notification) } } // MARK: - Required Initializer init(coordinate: CLLocationCoordinate2D) { self.coordinate = coordinate } } 

• Declare pin view as draggable:

   // MARK: - MKMapViewDelegate Actions func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? { let pinView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: pinViewReuseIdentifier) pinView.draggable = true return pinView } 

---

Now, when the pin is dragged, it invokes the delegate method:

func mapView(mapView: MKMapView, didSelectAnnotationView view: MKAnnotationView)

Here, you can retrieve the new end coordinates.

---

Alternatively, you could create a userInfo dictionary for the custom annotation's coordinate property's notifications. Observers could then retrieve the values upon receipt of the notification.

Answer 6

In Swift my problem was that the coordinate attribute was a let in my subclass and not a var as it is in the MKAnnotation .

class MyAnnotation  : NSObject, MKAnnotation {

    let title       : String?
    let subtitle    : String?
    var coordinate  : CLLocationCoordinate2D

    init(title: String, subtitle: String, coordinate: CLLocationCoordinate2D) {
        self.title = title
        self.subtitle = subtitle
        self.coordinate = coordinate
        super.init()
    }
}