Thank u~ once the same case happened on my pentax k10d, which i solve it on menu?
By default the lens should autofocus when you have it in A mode. You may have switched the camera to manual focus somewhere in a menu, but that's hardly something you could have done accidentally. Without knowing further details i'd reset the camera
Pentax is a brand name used by Pentax Ricoh Imaging Company for cameras, sport optics (e.g. binoculars), etc., Hoya Corporation for its medical-related products & services, TI Asahi for its surveying...