scrollView在iOS11新增的兩個(gè)屬性：adjustContentInset 和 contentInsetAdjustmentBehavior草讶。
/* When contentInsetAdjustmentBehavior allows, UIScrollView may incorporate
its safeAreaInsets into the adjustedContentInset.
*/
@property(nonatomic, readonly) UIEdgeInsets adjustedContentInset API_AVAILABLE(ios(11.0),tvos(11.0));
adjustContentInset表示contentView.frame.origin偏移了scrollview.frame.origin多少；是系統(tǒng)計(jì)算得來(lái)的闭专，計(jì)算方式由contentInsetAdjustmentBehavior決定。有以下幾種計(jì)算方式：
UIScrollViewContentInsetAdjustmentAutomatic：如果
scrollview在一個(gè)automaticallyAdjustsScrollViewContentInset = YES的controller上侥涵，并且這個(gè)Controller包含在一個(gè)navigation controller中卖陵，這種情況下會(huì)設(shè)置在top & bottom上adjustedContentInset = safeAreaInset + contentInset不管是否滾動(dòng)。其他情況下與UIScrollViewContentInsetAdjustmentScrollableAxes相同UIScrollViewContentInsetAdjustmentScrollableAxes: 在可滾動(dòng)方向上
adjustedContentInset = safeAreaInset + contentInset侧啼，在不可滾動(dòng)方向上adjustedContentInset = contentInset牛柒；依賴(lài)于scrollEnabled和alwaysBounceHorizontal / vertical = YES，scrollEnabled默認(rèn)為yes痊乾，所以大多數(shù)情況下皮壁，計(jì)算方式還是adjustedContentInset = safeAreaInset + contentInsetUIScrollViewContentInsetAdjustmentNever:
adjustedContentInset = contentInsetUIScrollViewContentInsetAdjustmentAlways:
adjustedContentInset = safeAreaInset + contentInset
當(dāng)contentInsetAdjustmentBehavior設(shè)置為UIScrollViewContentInsetAdjustmentNever的時(shí)候，adjustContentInset值不受SafeAreaInset值的影響哪审。
