Problem of Three20: How to refresh TTLauncherItem

Question

After adding TTLauncherItem into TTLauncherView, I want to change the image and title for the added TTLauncherItem。

But when I changed the value of image and title, it was not working. There is no change on the view.

Exit the program, and enter again, the image and title was changed.

How can I refresh image and title of TTLauncherItem immediately？

Thanks all～～