如何将UIScrollView移动一帧的宽度？(Xcode， Swift)

我正在尝试制作一款应用程序，该应用程序使用与Snapchat类似的功能，用户可以在水平相邻的3帧之间滑动。一切似乎都正常，但默认情况下，滚动视图会在最左边显示视图，并允许用户向右滑动两次以到达最右边的视图。我希望滚动视图首先显示中间视图，允许用户向左或向右滑动，但似乎无法获得。提前谢谢。

class ViewController: UIViewController {
@IBOutlet weak var scrollView: UIScrollView!
override func viewDidLoad() {
super.viewDidLoad()
scrollView.frame = self.view.bounds
let ViewOne = HomeViewController(nibName: "HomeViewController", bundle: nil)
ViewOne.view.frame = self.view.bounds
let ViewTwo = ExploreViewController(nibName: "ExploreViewController", bundle: nil)
ViewTwo.view.frame = self.view.bounds
let ViewThree = ProfileViewController(nibName: "ProfileViewController", bundle: nil)
ViewThree.view.frame = self.view.bounds
self.addChildViewController(ViewOne)
self.scrollView.addSubview(ViewOne.view)
ViewOne.didMove(toParentViewController: self)
self.addChildViewController(ViewTwo)
self.scrollView.addSubview(ViewTwo.view)
ViewTwo.didMove(toParentViewController: self)
self.addChildViewController(ViewThree)
self.scrollView.addSubview(ViewThree.view)
ViewThree.didMove(toParentViewController: self)
ViewTwo.view.center = CGPoint(x: ViewOne.view.center.x + self.view.frame.width, y: self.view.center.y)
ViewThree.view.center = CGPoint(x: ViewOne.view.center.x - self.view.frame.width, y: self.view.center.y)
scrollView.contentSize = CGSize(width: self.view.frame.width * 3, height: self.view.frame.height)
print(self.view.center.x)
}