contentSize膏燕、contentInset和contentOffset 是 scrollView三個(gè)基本的屬性。
contentSize: The size of the content view. 其實(shí)就是scrollview可以滾動(dòng)的區(qū)域悟民，比如frame = (0 ,0 ,320 ,480) contentSize = (320 ,960)坝辫，代表你的scrollview可以上下滾動(dòng)，滾動(dòng)區(qū)域?yàn)閒rame大小的兩倍射亏。
contentOffset:The point at which the origin of the content view is offset from the origin of the scroll view. 是scrollview當(dāng)前顯示區(qū)域頂點(diǎn)相對(duì)于frame頂點(diǎn)的偏移量近忙，比如上個(gè)例子你拉到最下面，contentoffset就是(0 ,480)智润，也就是y偏移了480
contentInset:The distance that the content view is inset from the enclosing scroll view.是scrollview的contentview的頂點(diǎn)相對(duì)于scrollview的位置及舍，例如你的contentInset = (0 ,100)，那么你的contentview就是從scrollview的(0 ,100)開始顯示
