swift playground tutorial

When doing the project, assume that when using the system's Uitabbarcontroller, the bottom tab itself defines the picture to be blue and gray. This is not the effect we want.Suppose you want to display your own defined, pressed and bouncing picture effects. At this time, the Tabbaritem needs to be changed.Here is a detailed demo sample:var itemnamearray:[String] = ["down_32","add_32", "Plane_32" , "Circle_32" ]var itemnameselectarray:[String] = ["down_click_32","Add_click_32" ,"plane_click_32",

the task and execute the task. First open Xcode to build a new project, select the Swift language, then just modify the default created Viewcontroller(1) Define an abstract implementation scheme (protocol), which follows the implementation of two eventsProtocol hwcsleepdelegate{func Willstarttosleep ()func Didfinishedsleep ()}(2) Define function classes to simulate long-time tasksclass hwcsleep{ var delegate:hwcsleepdelegate?func starttosleep (time