问在滚动视图中嵌入3个视图控制器

EN

    let storyboard = UIStoryboard(name: "Main", bundle: Bundle.main)

    self.mainScrollView.delaysContentTouches = false

    let v1 = storyboard.instantiateViewController(withIdentifier: "profileViewController") as! profileViewController

    self.addChildViewController(v1)
    self.mainScrollView.addSubview(v1.view)
    v1.didMove(toParentViewController: self)

    //--------

    let v2 : recordViewController = recordViewController(nibName: "recordViewController", bundle: nil)

    self.addChildViewController(v2)
    self.mainScrollView.addSubview(v2.view)
    v2.didMove(toParentViewController: self)

    //--------

    let v3 = storyboard.instantiateViewController(withIdentifier: "discoverViewController") as! discoverViewController

    self.addChildViewController(v3)
    self.mainScrollView.addSubview(v3.view)
    v3.didMove(toParentViewController: self)


    //--------
    var v1frame : CGRect = self.mainScrollView.bounds
    v1frame.origin.x = 0
    v1.view.frame = v1frame

    var v2frame : CGRect = self.mainScrollView.bounds
    v2frame.origin.x = self.view.frame.width
    v2.view.frame = v2frame

    var v3frame : CGRect = self.mainScrollView.bounds
    v3frame.origin.x = self.view.frame.width*2
    v3.view.frame = v3frame

    //v1.view.translatesAutoresizingMaskIntoConstraints = false

    let csH1 = NSLayoutConstraint.constraints(withVisualFormat: "|-[v]-|", options: [.alignAllTop], metrics: [:], views: ["v": v1.view])
    let csH2 = NSLayoutConstraint.constraints(withVisualFormat: "|-[v]-|", options: [.alignAllTop], metrics: [:], views: ["v": v2.view])
    let csH3 = NSLayoutConstraint.constraints(withVisualFormat: "|-[v]-|", options: [.alignAllTop], metrics: [:], views: ["v": v3.view])

    let csB1 = NSLayoutConstraint.constraints(withVisualFormat: "|-[v]-|", options: [.alignAllBottom], metrics: [:], views: ["v": v1.view])
    let csB2 = NSLayoutConstraint.constraints(withVisualFormat: "|-[v]-|", options: [.alignAllBottom], metrics: [:], views: ["v": v2.view])
    let csB3 = NSLayoutConstraint.constraints(withVisualFormat: "|-[v]-|", options: [.alignAllBottom], metrics: [:], views: ["v": v3.view])

    self.mainScrollView.addConstraints(csH1)
    self.mainScrollView.addConstraints(csH2)
    self.mainScrollView.addConstraints(csH3)

    self.mainScrollView.addConstraints(csB1)
    self.mainScrollView.addConstraints(csB2)
    self.mainScrollView.addConstraints(csB3)



    //UI
    self.mainScrollView.contentSize = CGSize(width: self.view.frame.width * 3, height: self.view.frame.size.height)
    self.mainScrollView.setContentOffset(CGPoint(x: self.view.frame.width, y: 0), animated: false)