Here we have a video demonstration of how to pickup items that are “behind” a portal, or too close to it to pick up by just direct tapping the item.
NOTE: This method has been mostly replaced by the new “intention filter” or “entity picker” as outlined here http://fevgames.net/ingress/ingress-guide/actions/droppick-up/ and here http://fevgames.net/ingress-apk-teardown-1-76-0/