uiviewcontroller顶级布局控制

@available(iOS 7.0, *)

open var edgesForExtendedLayout: UIRectEdge // Defaults to UIRectEdgeAll

@available(iOS 7.0, *)

open var extendedLayoutIncludesOpaqueBars: Bool // Defaults to NO, but bars are translucent by default on 7_0.

@available(iOS, introduced: 7.0, deprecated: 11.0, message: "Use UIScrollView's contentInsetAdjustmentBehavior instead")

open var automaticallyAdjustsScrollViewInsets: Bool // Defaults to YES

// Called just before the view controller's view's layoutSubviews method is invoked. Subclasses can implement as necessary. The default is a nop.

@available(iOS 5.0, *)

open func viewWillLayoutSubviews()

preferredContentSize

self.edgesForExtendedLayout = UIRectEdgeAll;

self.extendedLayoutIncludesOpaqueBars = YES;

self.automaticallyAdjustsScrollViewInsets = NO;

if #available(iOS 11.0, *){

scrollView.contentInsetAdjustmentBehavior = .never

} else {

self.automaticallyAdjustsScrollViewInsets = false

// Fallback on earlier versions

}