Show annotation AFTER the pin is dropped?

I have been checking a couple of related posts regarding the callout behaviour. I know didAddAnnotationViews could bring annotation view along with the pin when it starts dropping. But what I开发者_高级运维 actually want is show the annotation AFTER the pin is dropped onto the map, just like when you search an address in "Maps" application on iPhone, the pin drops on the map, and then the annotation pops up. Does anyone know how to do that? Do I need to do some customisation on the annotation view? Thanks.