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I am trying to stick the UIView on top while scrolling. Tried using max(x:T, y:T) method as suggested here on stackOverflow but it does not work. I manage to detect when the scrollView should be re-positioned but updating frame does not have any affect.

import UIKit

class ViewController: UIViewController, UIScrollViewDelegate{

@IBOutlet var objectView: UIView!
@IBOutlet var scrollView: UIScrollView!

//var originalOffsetY : CGFloat!
//var originalOffestX : CGFloat!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    let size = CGSize.init(width: self.view.frame.width, height: self.view.frame.height*2)
    scrollView.contentSize = size
    scrollView.backgroundColor = UIColor.blueColor()
    objectView.backgroundColor = UIColor.whiteColor()
    scrollView.delegate = self

    scrollView.addSubview(objectView)
}

    // override func viewWillAppear(animated: Bool) {
    // originalOffsetY = objectView.frame.origin.y
    // originalOffestX = objectView.frame.origin.x

    // } 


func scrollViewDidScroll(scrollView: UIScrollView) {

    print("ScrollView \(scrollView.contentOffset.y)")
    print("ObjectView \(objectView.frame.origin.y)")


    let location = CGPointMake(0, scrollView.contentOffset.y)
    let size = objectView.frame.size


    if scrollView.contentOffset.y >= objectView.frame.origin.y {
        objectView.frame = CGRect.init(origin: location, size: size)
        print("Detected \(objectView.frame)")

    }

    //        var newRect = objectView.frame
    //        newRect.origin.y = max(originalOffsetY!, scrollView.contentOffset.y)
    //        objectView.frame = newRect


}

}

The condition is matched successfully as can be seen here in Logs . But the view remains unchanged. I require the objectView to scroll a bit.. from around y=270 to 0 .. but not beyond it.

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user3626615
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    If you need objectView to stay put as scrollView is scrolled, instead of making it a subview of scrollView, why not make them sibling views instead (i.e. make objectView a subview of your viewController's view alongside scrollview)? This is the way I've done things when trying to implement a search bar on a table view, for instance - generally speaking I find it much simpler! – Marcus Sep 17 '16 at 15:53
  • @Sparky - I need the objectView to scroll a bit.. from around y=270 to 0 .. but not beyond it. – user3626615 Sep 17 '16 at 17:38

1 Answers1

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You need to keep track of the original position of the view within the scroll view, and calculate using that value, here's a very simplified example:

class StickyScrollViewController: UIViewController {

    var stickyView = UIView(frame: CGRect(x: 0, y: 100, width: 300, height: 100))
    var originalStickyOrigin: CGPoint = CGPoint(x: 0, y: 100)

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        var nextYOffset = max(originalStickyOrigin.y, scrollView.contentOffset.y)
        stickyView.frame = CGRect(x: 0, y: nextYOffset, width: 300, height: 100)
    }
}
Dave Lyon
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