UIScrollView在iOS11上的新变化

automaticallyAdjustsScrollViewInsets
A Boolean value that indicates whether the view controller should automatically adjust its scroll view insets.
iOS 7.0–11.0Deprecated
tvOS 9.0–11.0Deprecated

看看官方的废气声明

QQ20170915-101510.png

再来看看官方对该属性的替换说明

@property(nonatomic,assign) BOOL automaticallyAdjustsScrollViewInsets API_DEPRECATED_WITH_REPLACEMENT("Use UIScrollView's contentInsetAdjustmentBehavior instead", ios(7.0,11.0),tvos(7.0,11.0)); // Defaults to YES

所以需要我们使用contentInsetAdjustmentBehavior来替换，这个属性究竟是干什么用的？

QQ20170915-101820.png

进而研究一下该Behavior都有哪些状态可供选择：

英文版：
typedef NS_ENUM(NSInteger, UIScrollViewContentInsetAdjustmentBehavior) {
    UIScrollViewContentInsetAdjustmentAutomatic, // Similar to .scrollableAxes, but for backward compatibility will also adjust the top & bottom contentInset when the scroll view is owned by a view controller with automaticallyAdjustsScrollViewInsets = YES inside a navigation controller, regardless of whether the scroll view is scrollable
    UIScrollViewContentInsetAdjustmentScrollableAxes, // Edges for scrollable axes are adjusted (i.e., contentSize.width/height > frame.size.width/height or alwaysBounceHorizontal/Vertical = YES)
    UIScrollViewContentInsetAdjustmentNever, // contentInset is not adjusted
    UIScrollViewContentInsetAdjustmentAlways, // contentInset is always adjusted by the scroll view's safeAreaInsets
} API_AVAILABLE(ios(11.0),tvos(11.0));

中文版：
typedef NS_ENUM(NSInteger, UIScrollViewContentInsetAdjustmentBehavior) {
    UIScrollViewContentInsetAdjustmentAutomatic, // 与.scrollableAxes相似,但为了向后兼容依然会对navigationController里的且设置或者默认为automaticallyAdjustsScrollViewInsets = YES的scrollView来调整top和bottom contentInset，无论是否设置了scrollView的可滑动属性scrollable。
    UIScrollViewContentInsetAdjustmentScrollableAxes, // 可理解为可滑动轴边缘始终会被调整（例如：contentSize.width/height > frame.size.width/height or alwaysBounceHorizontal/Vertical = YES） 
    UIScrollViewContentInsetAdjustmentNever, // contentInset 不会被调整
    UIScrollViewContentInsetAdjustmentAlways, // contentInset 始终会被scrollView的safeAreaInsets来调整
}(ios(11.0),tvos(11.0))可见;

在iOS11之前，系统会通过动态调整UIScrollView的contentInset属性来实现视图内容的偏移，但是在iOS11中，系统不再调整UIScrollView的contentInset，而是通过contentInsetAdjustmentBehavior和adjustedContentInset来配合完成。

所以遇到NavigationController被隐藏的页面时，如果内部视图为scrollview或其子类tableView等，iOS11下将默认采用UIScrollViewContentInsetAdjustmentAutomatic属性，自然视图会被下移到UIStatusBar下（如果你的布局为scrollview.top = superview.top），这时我们只需要将scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;即可。注意这里是对scrollview设置的，而iOS11之前，我们设置不要自动偏移的行为则是对当前的UIViewController进行的。 self.automaticallyAdjustsScrollViewInsets = NO;

if (@available(iOS 11.0, *)) {
    scrollView.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
} else {
    self.automaticallyAdjustsScrollViewInsets = NO;
}