It adds the controller's view as a subview of the window.

它创建了一个视图控制对象用来管理窗口视图对象的内容。

youdao

How to find the kind of subview object the view is containing in it?

如何找到对象视图的子视图包含吗?。

youdao

One way I can do is to set the leading space and trailing space of the top subview with respect to the main view and also centering horizontally in the main view.

我可以做的一个方法是设置顶部子视图相对于主视图的前导空格和尾随空格，并且在主视图中水平居中。

youdao

This would give you a scroll view that resized as the view controller's view resized (such as on device rotation), and the image view would be a scrolling subview.

ENGADGET: Apple seeds iOS 6 beta 4 to developers: here's the changelog

Note that you can make a subview of the scroll view appear to float (not scroll) over the other scrolling content by creating constraints between the view and a view outside the scroll view's subtree, such as the scroll view's superview.

ENGADGET: Apple seeds iOS 6 beta 4 to developers: here's the changelog