How to control UIMenuController, in case I do not want it hide automatically?

I'm doing a chat tool, with a UITextField as input. The p开发者_如何转开发roblem is, when other UI control updates, like messages scroll on new arrivals, the UIMenuController, if currently visible, automatically hides. How can I forbid such automation? Even I can catch the event with UIMenuControllerWillHideMenuNotification or UIMenuControllerDidHideMenuNotification, there's no way I can control it.

Did u try its instance method

setMenuVisible:(BOOL)menuVisible animated:(BOOL)animated