Progress of UIPageViewController

Question

I would like to receive updates from the uipageviewcontroller during the page scrolling process. I want to know the transitionProgress in %. (This value should update when t

Answer 1

KVO approach for Swift 4

var myContext = 0

override func viewDidLoad() {
    for view in self.view.subviews {
        if view is UIScrollView {
            view.addObserver(self, forKeyPath: "contentOffset", options: .new, context: &introPagingViewControllerContext)
        }
    }
}

// MARK: KVO

override func observeValue(forKeyPath keyPath: String?,
                           of object: Any?,
                           change: [NSKeyValueChangeKey : Any]?,
                           context: UnsafeMutableRawPointer?)
{
    guard let change = change else { return }
    if context != &myContext {
        super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
        return
    }

    if keyPath == "contentOffset" {
        if let contentOffset = change[NSKeyValueChangeKey.newKey] as? CGPoint {
            let screenWidth = UIScreen.main.bounds.width
            let percent = abs((contentOffset.x - screenWidth) / screenWidth)
            print(percent)
        }
    }
}