ios - UITabBarController switch tab is slow at first time -

i working on ipad project uitabbarcontroller (it's root) has 5 tabs.

the second tab tableview there quite rich ui elements.

the problem everytime launch app , click second tab, blocked 0.3 second show viewcontroller. however, after first time enter tab, takes me 0.03 enter tab again.

so thought viewdidload cost much, because lot addsubview or reloaddata there. add

[libraryvc viewdidload]; [libraryvc viewwillappear:yes]; [libraryvc viewdidappear:yes]; 

in application:didfinishlaunchingwithoptions, think if view load stuff before user enter second tab, there no block.

however after tested approach, found cost not reduced. guess time cost may used in view render when first show viewcontroller. when viewcontroller's view has been rendered before, following show fast. have no idea solve problem.

i think problem common when viewcontroller's view complicated, has idea of approach solve problem? or can give detail description of reason why block happens?

thanks help!

perhaps multithreading time intensive methods/calls solution looking for. if search "ios grand central dispatch" on google, great resources available. apple's grand central dispatch reference 1 of better pieces of documentation have.