Offset UIScrollView from a child ViewController

Question

I currently have an application with a UI Similar to the Snapchat ScrollView. The MainViewController contains a UIScroll, in which three child ViewControllers are added as child ViewControllers:

override func viewDidLoad() {

    super.viewDidLoad()
    scrollView.contentSize = CGSizeMake((self.view.bounds.width*3 + 4), self.view.bounds.height)
    self.view.addSubview(scrollView)

    let view1 = UIView(frame: CGRectMake(0, 0, self.view.bounds.width, self.view.bounds.height))
    scrollView.addSubview(view1)
    let aVC = self.storyboard?.instantiateViewControllerWithIdentifier("One")
    view1.addSubview(aVC!.view)
    self.addChildViewController(aVC!)

    let view2 = UIView(frame: CGRectMake((self.view.bounds.width), 0, self.view.bounds.width, self.view.bounds.height))
    scrollView.addSubview(view2)
    let bVC = self.storyboard?.instantiateViewControllerWithIdentifier("Two")
    view2.addSubview(bVC!.view)
    self.addChildViewController(bVC!)

    let view3 = UIView(frame: CGRectMake(2*view.bounds.width), 0, self.view.bounds.width, self.view.bounds.height))
    scrollView.addSubview(view3)
    let cVC = self.storyboard?.instantiateViewControllerWithIdentifier("LocationViewController")
    view3.addSubview(cVC!.view)
    self.addChildViewController(cVC!)

    scrollView.contentOffset = CGPointMake(self.view.frame.width, 0
    }

I attempting to add buttons two the middle ViewController, which will offset the ScrollView to either the left or right View Controllers. I know I can use setContentOffset() in the MainViewController, but I cannot call this in the child view controllers. Both self.presentingViewController and self.parentViewController both return nil.

What is the best way to call setContentOffset() for the UIScrollView, within a child ViewController?

GetSwifty GetSwifty · Accepted Answer · 2016-03-21T22:39:38

This seems like a good use case for delegation. Add a delegate to the ViewControllers with views that will change, then have your parent ViewController get itself as the delegate. Then you can inspect the views and resize accordingly.

Offset UIScrollView from a child ViewController

1 Answers