酸梅拯救地球

摘要： 1.This is a unique instance ofUINavigationItemcreated to represent the view controller when it is pushed onto a navigation controller. The first time the property is accessed, theUINavigationItemobject is created. Therefore, you shouldn’t access this property if you are not using a navigation contro 阅读全文

摘要： 1.When you present a modal view controller, the system creates a relationship between the view controller that did the presenting and the view controller that was presented. Specifically, the view controller that did the presenting updates itspresentedViewControllerproperty to point to its presented 阅读全文