Background: I have created an application that allows users to submit an entry to an online database, and view other entries from that database. These entries contain geocodes for latitude and longitude which are used for positioning the annotations on the MapKit. Users can submit the location using either their current location or an address, which is then geocoded.
Question: What is the proper or suggested method of handling annotations that fall on the exact same coordinates?
I was thinking of checking if there are any duplicate geocodes in the XML file pulled from the database and creating a single annotation with a custom annotationView that displays all of the separate ones. In addition, I was thinking of checking for duplicates and displaying "Multiple Entries..." and having the detail view display a table view with all of the entries.
Am I on the right track?
I think you are on the right track, you should check for duplicate geocodes and merge them into one. Displaying many annotations with the same location could be confusing because the pins will stack on top of each other and will be hard to diffrentiate and to click one by one.
Are you talking exact same geocode or kinda sorta close? Because if it's exact, then you're on the right track, but if it's +/- delta-T then you may have to come up with a different way of handling them since when zoomed-in all the way each location could be distinct. An easy way to hanle it is to drop or round-off decimal points in the lat/long value based on the zoom factor before checking for coordinate equality.
Other than that it sounds like you're on the right track. You will probably want to do both the custom annotation view (but that could work for only a few items) with the option to move on to a separate table view if there are more items to show.
One other thing I'd add is you could make it so your placemarker shows the number of items that co-reside in that location. You can do this by sticking a text label on top of your custom placemarker view and putting the number in it or by having pre-rendered icons with say, 1-9 and "..." (for more than that) in the heads of the markers. That way the user can quickly see there's more items to look for.
来源：https://stackoverflow.com/questions/1322509/iphone-3-0-mapkit-multiple-annotations-in-the-same-location