How to change UINavigationBar background image - iphone sdk?

first of all, i read all "changing uinavigationbar color & backgound image",开发者_如何学Go but i couldnt get over my problem.

i have a tabbar app with 4 tabs. each tab has navigationcontroller. (i arranged all the objects in mainwindow.xib file in IB)

in thew first tab, i wanna display 1.jpg on navigationbars background image in first view. when the use taps the tableviews row, how can i display "2.jpg" on navigationbar for second view?

i also wanna display different images for each tabs.

how can i solve it?

thanx for all.

---

you can do self.navigationController.navigationBar.layer.contents = (id)image.CGImage to change the navigation bar's background.