timer issue at displaying view

hi i am new to iphone. what i am doign is displaying 20 images as grid and by selecting image it is displayed on imageview after 4 sec it will come back to main screen,for that i am using timer it works fine but there is a sm开发者_开发技巧all problem with out selecting image the timer is continually running.if i am selecting button on 2 sec late then with in remaining 2 sec it will come back how can i solve this pls help me

Instead of having the timer continuously running, only start it when the user selects an image. That way you get the full 4 seconds. Also, make sure you set it not to repeat.

In the selector you're calling with your timer, you need to invalidate that timer. That means you need to assign the timer to a property in your view controller, so you can talk about it later. So say you've got an ivar of NSTimer *backTimer, then in the method that the timer calls, you'll say [backTimer invalidate], and that timer will go away.

You should also invalidate it when somebody backs out of the "full image" view. Probably in -viewDidUnload or -viewDidDissapear.