摘要： Any time a user interacts with your user interface, or any time your own code programmatically changes something, a complex sequence of events takes p 阅读全文

摘要： The UIView class uses an on-demand drawing model for presenting content. When a view first appears on the screen, the system asks it to draw its conte 阅读全文

摘要： A view object defines a rectangular region on the screen and handles the drawing and touch events in that region. A view can also act as a parent for 阅读全文