View does not stick on top (does not change position) - ios

Question

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.

Answer 1

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)
}
}