Swift-解决NavigationBar遮挡住view内容的问题

edgesForExtendedLayout

The extended edges to use for the layout.

automaticallyAdjustsScrollViewInsets

A Boolean value that indicates whether the view controller should automatically adjust its scroll view insets.

extendedLayoutIncludesOpaqueBars
A Boolean value indicating whether or not the extended layout includes opaque bars.

代码示例：

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.
    //解决 NavigationBar 挡住 view 内容的问题
    //将edgesForExtendedLayout设置成UIRectEdgeNone,表明View是不要扩展到整个屏幕的
    self.edgesForExtendedLayout = UIRectEdge.None

    //打印查看:automaticallyAdjustsScrollViewInsets默认为true
    //print(self.automaticallyAdjustsScrollViewInsets.boolValue)
    //self.automaticallyAdjustsScrollViewInsets

    ... ...
}

参考：

http://www.cocoachina.com/bbs/read.php?tid=153502
http://www.cocoachina.com/bbs/read.php?tid-195157-page-e-fpage-705.html
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