設(shè)置按頁滾動時篙贸，注意設(shè)置pagingEnabled屬性禽篱，只有這樣八千，滾動才會一頁頁滾動慷吊。
1.bounds屬性：origin為當(dāng)前內(nèi)容偏移量
2.frame屬性：scrollview本身的大小
3.contentsize屬性：包含內(nèi)容的大小
4.contentoffset屬性：內(nèi)容偏移量
5.center屬性：scrollview本身的中心
如下示例
(lldb) po (CGRect)[self.contentScrollView bounds]
(origin = (x = 1280, y = 0), size = (width = 320, height = 379))
(origin = (x = 1280, y = 0), size = (width = 320, height = 379))
(lldb) po (CGRect)[self.contentScrollView frame]
(origin = (x = 0, y = 52), size = (width = 320, height = 379))
(origin = (x = 0, y = 52), size = (width = 320, height = 379))
(lldb) po (CGSize)[self.contentScrollView contentSize]
(width = 1920, height = 0)
(width = 1920, height = 0)
(lldb) po (CGPoint)[self.contentScrollView contentOffset]
(x = 1280, y = 0)
(x = 1280, y = 0)
(lldb) po (CGPoint)[self.contentScrollView center]
(x = 160, y = 241.5)
(x = 160, y = 241.5)
