如何轻轻地从地图视图中删除注释？

Question

I'm adding and removing annotations to a map view. When I remove one it disappears abruptly and looks a bit startling, I'd rather it faded away gracefully.

I tried removing it with UIView:animateWithDuration: but it wasn't an animatable attribute.

If there's no other easy solution I was thinking I could get the annotation view to fade its alpha and then remove its annotation from the map. However the problem with this is it doesn't seem like an annotation view has a reference to its map view? Adding one starts to get a bit messy. Is there some easy quick solution to removing an annotation gracefully?

Answer 1

Using animateWithDuration should work fine. To fade the removal of an annotation, one can:

MKAnnotationView *view = [self.mapView viewForAnnotation:annotation];

if (view) {
    [UIView animateWithDuration:0.5 delay:0.0 options:0 animations:^{
        view.alpha = 0.0;
    } completion:^(BOOL finished) {
        [self.mapView removeAnnotation:annotation];
        view.alpha = 1.0;   // remember to set alpha back to 1.0 because annotation view can be reused later
    }];
} else {
    [self.mapView removeAnnotation:annotation];
}

Answer 2

I think your proposed solution is the correct one. Set up an animation to opacity = 0, then, upon completion, remove the annotation from the MKMapView . The code that starts the animation doesn't have to be in the view itself; a better location for the code may be the view controller. Consider using NSNotificationCenter to notify the view controller that an annotation is requesting fade-out-and-remove.