问题
How does one get a list (array) of currently visible overlay from a MapkitView?
Background - for example I want to show direction arrows to the center of certain Overlay types on my mapkitview, however how do I get the visible ones? There seems to be no way to do this I can see? So do I need to got through all overlays (actually ~8000) and do my own check to see what would be showing on the screen? Seems a waste if MapKit would have already effectively done this as part of deciding what overlays need to be displayed at a given time.
回答1:
I've been tinkering with some similar problems and the most efficient way I could figure out was to add the overlays as annotations as well, since MKOverlay implements MKAnnotation. Then you would be able to use annotationsInMapRect for the currently displayed mapRect. However this would also return any regular MKAnnotations, and only uses the calculated middle of the overlay. The only way (so far as I figured) to only get the overlays would be to iterate over each overlay and use:
-(BOOL)intersectsMapRect:(MKMapRect)mapRect;
on the currently visible mapRect. If you found another way I'd be happy to hear!
来源：https://stackoverflow.com/questions/37433336/how-to-get-visible-overlays-in-mapkit-i-e-mkoverlay-mkoverlayrender-from-a-ma