MKAnnotationView drag state ending animation

Question

I'm using the custom MKAnnotationView animations provided by Daniel here: Subclassing MKAnnotationView and overriding setDragState but I run into an issue.

After the pin drop animation, when I go to move the map the mkannotationview jumps back to its previous location before the final pin drop animation block is called.

It seems to me that dragState=MKAnnotationViewDragStateEnding is being called before the animation runs? How can I get around this issue and set the final point of the mkannotationview to be the point it's at when the animation ends?

#import "MapPin.h"

NSString *const DPAnnotationViewDidFinishDrag = @"DPAnnotationViewDidFinishDrag";
NSString *const DPAnnotationViewKey = @"DPAnnotationView";

// Estimate a finger size
// This is the amount of pixels I consider
// that the finger will block when the user
// is dragging the pin.
// We will use this to lift the pin even higher during dragging

#define kFingerSize 20.0

@interface MapPin()
@property (nonatomic) CGPoint fingerPoint;
@end

@implementation MapPin
@synthesize dragState, fingerPoint, mapView;

- (void)setDragState:(MKAnnotationViewDragState)newDragState animated:(BOOL)animated
{
    if(mapView){
        id<MKMapViewDelegate> mapDelegate = (id<MKMapViewDelegate>)mapView.delegate;
        [mapDelegate mapView:mapView annotationView:self didChangeDragState:newDragState fromOldState:dragState];
    }

    // Calculate how much to life the pin, so that it's over the finger, no under.
    CGFloat liftValue = -(fingerPoint.y - self.frame.size.height - kFingerSize);

    if (newDragState == MKAnnotationViewDragStateStarting)
    {
        CGPoint endPoint = CGPointMake(self.center.x,self.center.y-liftValue);
        [MapPin animateWithDuration:0.2
                         animations:^{
                             self.center = endPoint;
                         }
                         completion:^(BOOL finished){
                             dragState = MKAnnotationViewDragStateDragging;
                         }];

    }
    else if (newDragState == MKAnnotationViewDragStateEnding)
    {
        // lift the pin again, and drop it to current placement with faster animation.

        __block CGPoint endPoint = CGPointMake(self.center.x,self.center.y-liftValue);
        [MapPin animateWithDuration:0.2
                         animations:^{
                             self.center = endPoint;
                         }
                         completion:^(BOOL finished){
                             endPoint = CGPointMake(self.center.x,self.center.y+liftValue);
                             [MapPin animateWithDuration:0.1
                                              animations:^{
                                                  self.center = endPoint;
                                              }
                                              completion:^(BOOL finished){
                                                  dragState = MKAnnotationViewDragStateNone;
                                                  if(!mapView)
                                                      [[NSNotificationCenter defaultCenter] postNotificationName:DPAnnotationViewDidFinishDrag object:nil userInfo:[NSDictionary dictionaryWithObject:self.annotation forKey:DPAnnotationViewKey]];
                                              }];
                         }];
    }
    else if (newDragState == MKAnnotationViewDragStateCanceling)
    {
        // drop the pin and set the state to none

        CGPoint endPoint = CGPointMake(self.center.x,self.center.y+liftValue);
        [UIView animateWithDuration:0.2
                         animations:^{
                             self.center = endPoint;
                         }
                         completion:^(BOOL finished){
                             dragState = MKAnnotationViewDragStateNone;
                         }];
    }
}

- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent*)event
{
    // When the user touches the view, we need his point so we can calculate by how
    // much we should life the annotation, this is so that we don't hide any part of
    // the pin when the finger is down.

    fingerPoint = point;
    return [super hitTest:point withEvent:event];
}

@end

Answer 1

I had the same problem, especially under iOS 8. After many hours of testing I believe that iOS keeps track of where it thinks self.center of the annotation is during the time that the state is MKAnnotationViewDragStateDragging. You need to use extreme caution if you animate self.center when handling MKAnnotationViewDragStateEnding. Read that as "I couldn't get that to work, ever."

Instead, I kept Daniel's original code when handling states MKAnnotationViewDragStateStarting and MKAnnotationViewDragStateCanceling, I animated self.center. When handling MKAnnotationViewDragStateEnding I animated self.transform instead of self.center. This maintains the actual location of the annotation and just changes how it is rendered.

This works well for me running either iOS 7.1 and iOS 8.0. Also fixed a bug in hitTest, and added some code to reselect the annotation after dragging or canceling. I think that is the default behavior of MKPinAnnotationView.

- (void)setDragState:(MKAnnotationViewDragState)newDragState animated:(BOOL)animated
{
    if(mapView){
        id<MKMapViewDelegate> mapDelegate = (id<MKMapViewDelegate>)mapView.delegate;
        [mapDelegate mapView:mapView annotationView:self didChangeDragState:newDragState fromOldState:dragState];
    }

    // Calculate how much to lift the pin, so that it's over the finger, not under.
    CGFloat liftValue = -(fingerPoint.y - self.frame.size.height - kFingerSize);

    if (newDragState == MKAnnotationViewDragStateStarting)
    {
        CGPoint endPoint = CGPointMake(self.center.x,self.center.y-liftValue);
        [UIView animateWithDuration:0.2
                         animations:^{
                             self.center = endPoint;
                         }
                         completion:^(BOOL finished){
                             dragState = MKAnnotationViewDragStateDragging;
                         }];

    }
    else if (newDragState == MKAnnotationViewDragStateEnding)
    {
        CGAffineTransform theTransform = CGAffineTransformMakeTranslation(0, -liftValue);
        [UIView animateWithDuration:0.2
                         animations:^{
                             self.transform = theTransform;
                         }
                         completion:^(BOOL finished){
                             CGAffineTransform theTransform2 = CGAffineTransformMakeTranslation(0, 0);
                             [UIView animateWithDuration:0.2
                                              animations:^{
                                                  self.transform = theTransform2;
                                              }
                                              completion:^(BOOL finished){
                                                  dragState = MKAnnotationViewDragStateNone;
                                                  if(!mapView)
                                                      [[NSNotificationCenter defaultCenter] postNotificationName:DPAnnotationViewDidFinishDrag object:nil userInfo:[NSDictionary dictionaryWithObject:self.annotation forKey:DPAnnotationViewKey]];
                                                  // Added this to select the annotation after dragging.
                                                  // This is the behavior for MKPinAnnotationView
                                                  if (mapView)
                                                      [mapView selectAnnotation:self.annotation animated:YES];
                                              }];
                         }];
    }
    else if (newDragState == MKAnnotationViewDragStateCanceling)
    {
        // drop the pin and set the state to none
        CGPoint endPoint = CGPointMake(self.center.x,self.center.y+liftValue);

        [UIView animateWithDuration:0.2
                         animations:^{
                             self.center = endPoint;
                         }
                         completion:^(BOOL finished){
                             dragState = MKAnnotationViewDragStateNone;
                             // Added this to select the annotation after canceling.
                             // This is the behavior for MKPinAnnotationView
                             if (mapView)
                                 [mapView selectAnnotation:self.annotation animated:YES];
                         }];
    }
}

- (UIView*)hitTest:(CGPoint)point withEvent:(UIEvent*)event
{
    // When the user touches the view, we need his point so we can calculate by how 
    // much we should life the annotation, this is so that we don't hide any part of
    // the pin when the finger is down.

    // Fixed a bug here.  If a touch happened while the annotation view was being dragged
    // then it screwed up the animation when the annotation was dropped.
    if (dragState == MKAnnotationViewDragStateNone)
    {
        fingerPoint = point;
    }
    return [super hitTest:point withEvent:event];
}