iOS只有一半的视图显示

Question

我有这个问题。所以我在横向滚动视图中使用切换屏幕制作这个Snapchat样式菜单。所有视图控制器都在一个故事板上。

let storyBoard = UIStoryboard(name: "Main", bundle: nil)
let V1 = storyBoard.instantiateViewControllerWithIdentifier("FirstViewController")
let V2 = storyBoard.instantiateViewControllerWithIdentifier("SecondViewController")
let V3 = storyBoard.instantiateViewControllerWithIdentifier("ThirdViewController")
let V4 = storyBoard.instantiateViewControllerWithIdentifier("FourthViewController")

self.addChildViewController(V1)
self.scrollView.addSubview(V1.view)
V1.didMoveToParentViewController(self)

self.addChildViewController(V2)
self.scrollView.addSubview(V2.view)
V2.didMoveToParentViewController(self)

self.addChildViewController(V3)
self.scrollView.addSubview(V3.view)
V3.didMoveToParentViewController(self)

self.addChildViewController(V4)
self.scrollView.addSubview(V4.view)
V4.didMoveToParentViewController(self)

var V2Frame : CGRect = V2.view.frame
V2Frame.origin.x = self.view.frame.width
V2.view.frame = V2Frame

var V3Frame : CGRect = V3.view.frame
V3Frame.origin.x = self.view.frame.width * 2
V3.view.frame = V3Frame

var V4Frame : CGRect = V4.view.frame
V4Frame.origin.x = self.view.frame.width * 3
V4.view.frame = V4Frame

self.scrollView.contentSize = CGSizeMake(self.view.frame.width * 4, self.view.frame.size.height)

但是，如前所述......每个视图中只有大约一半显示....