Why does the whole view jerk up when the keyboard hides?

Question

When the keyboardWillHideFunction is called the whole view from the viewController jerks upward. Below is a video of the probelm occuring.

vidoe of screen jerking

Below is the code I am using to control keyboard notifications. I have tried playing around with the animation times and the layout constraints but I havent been able to get much further. Any suggestions on how to fix it thank you.

EDITED CODE BASED ON SUGGESTIONS- Ive tried creating a variable for the layout constraints as suggested however the problem still persists any ideas why?

import UIKit
import Foundation

extension UIView {
    func currentFirstResponder() -> UIResponder? {
        if self.isFirstResponder {
            return self
        }

        for view in self.subviews {
            if let responder = view.currentFirstResponder() {
                return responder
            }
        }

        return nil
    }
}

extension Notification.Name{
    static let showKeyboard = Notification.Name("showKeyboard")
}

class KeyboardSlider: NSObject {
    // variables to hold and process information from the view using this class
    weak var view: UIView?
    var searchBarTopTags:SearchBarTopTagsViewController?
    var amountToShiftBy:CGFloat!
    var originalFrame:CGRect!
    var previewController:PreviewController!

    @objc func keyboardWillShow(notification: NSNotification) {
self.searchBarTopTags?.myViewBottomLayoutConstraint.constant =  -self.getKeyboardHeight(notification as! Notification) + previewController.view.safeAreaInsets.bottom
        UIView.animate(withDuration: 0, animations: {
            self.view?.layoutIfNeeded()
            self.searchBarTopTags?.myView.layoutIfNeeded()

        })
    }

    @objc func keyboardWillHide(notification:NSNotification){

        self.searchBarTopTags?.myViewBottomLayoutConstraint.constant = 0
        UIView.animate(withDuration: 0, animations: {
            self.view?.layoutIfNeeded()
            self.searchBarTopTags?.myView.layoutIfNeeded()
        })
    }
    func getKeyboardHeight(_ notification:Notification) -> CGFloat {
        // get exact height of keyboard on all devices and convert to float value to return for use
        let userInfo = notification.userInfo
        let keyboardSize = userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue
        return keyboardSize.cgRectValue.height
    }

    func subscribeToKeyboardNotifications(view: UIView) {
        // assigning view to class' counterpart
        self.view = view
        // when UIKeyboardWillShow do keyboardWillShow function
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
    }


    func subscribeToKeyboardNotifications(view: UIView, previewController:PreviewController? = nil) {
        // assigning view to class' counterpart
        self.view = view
        self.searchBarTopTags = previewController?.searchBarTopTags
        self.previewController = previewController

        // when UIKeyboardWillShow do keyboardWillShow function
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(notification:)), name: .UIKeyboardWillHide, object: nil)
    }


    func unsubscribeFromKeyboardNotifications() {
        NotificationCenter.default.removeObserver(self, name: .UIKeyboardWillShow, object: nil)
        NotificationCenter.default.removeObserver(self, name: .UIKeyboardWillHide, object: nil)
    }

}

ORIGINAL CODE:

import UIKit
import Foundation

extension UIView {
    func currentFirstResponder() -> UIResponder? {
        if self.isFirstResponder {
            return self
        }

        for view in self.subviews {
            if let responder = view.currentFirstResponder() {
                return responder
            }
        }

        return nil
    }
}

extension Notification.Name{
    static let showKeyboard = Notification.Name("showKeyboard")
}

class KeyboardSlider: NSObject {
    // variables to hold and process information from the view using this class
    weak var view: UIView?
    var searchBarTopTags:SearchBarTopTagsViewController?
    var amountToShiftBy:CGFloat!
    var originalFrame:CGRect!

    @objc func keyboardWillShow(notification: NSNotification) {
        self.originalFrame = self.searchBarTopTags?.myView.frame
        self.amountToShiftBy = (self.searchBarTopTags?.view.frame.maxY)! - self.getKeyboardHeight(notification as! Notification) - (self.searchBarTopTags?.myView.frame.height)!
        self.amountToShiftBy = (searchBarTopTags?.view.bounds.height)! - self.getKeyboardHeight(notification as! Notification) - (searchBarTopTags?.myView.bounds.height)!
        self.searchBarTopTags?.myView.bottomAnchor.constraint(equalTo: (self.searchBarTopTags?.view.bottomAnchor)!, constant: -self.amountToShiftBy).isActive = true

        UIView.animate(withDuration: 0, animations: {
            self.view?.layoutIfNeeded()
            self.searchBarTopTags?.view.layoutIfNeeded()
            self.searchBarTopTags?.myView.layoutIfNeeded()        })

    }

    @objc func keyboardWillHide(notification:NSNotification){

        self.searchBarTopTags?.myView.bottomAnchor.constraint(equalTo: (self.searchBarTopTags?.view.bottomAnchor)!, constant: 0).isActive = true
        UIView.animate(withDuration: 0, animations: {
            self.view?.layoutIfNeeded()
            self.searchBarTopTags?.view.layoutIfNeeded()
            self.searchBarTopTags?.myView.layoutIfNeeded()
        })
    }
    func getKeyboardHeight(_ notification:Notification) -> CGFloat {
        // get exact height of keyboard on all devices and convert to float value to return for use
        let userInfo = notification.userInfo
        let keyboardSize = userInfo![UIKeyboardFrameEndUserInfoKey] as! NSValue
        return keyboardSize.cgRectValue.height
    }

    func subscribeToKeyboardNotifications(view: UIView) {
        // assigning view to class' counterpart
        self.view = view
        // when UIKeyboardWillShow do keyboardWillShow function
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
    }


    func subscribeToKeyboardNotifications(view: UIView, seachBarTopTagsVC:SearchBarTopTagsViewController? = nil) {
        // assigning view to class' counterpart
        self.view = view
        self.searchBarTopTags = seachBarTopTagsVC

        // when UIKeyboardWillShow do keyboardWillShow function
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow(notification:)), name: .UIKeyboardWillShow, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillHide(notification:)), name: .UIKeyboardWillHide, object: nil)
    }


    func unsubscribeFromKeyboardNotifications() {
        NotificationCenter.default.removeObserver(self, name: .UIKeyboardWillShow, object: nil)
        NotificationCenter.default.removeObserver(self, name: .UIKeyboardWillHide, object: nil)
    }

}

Answer 1

Inside keyboardWillShow there is

self.searchBarTopTags?.myView.bottomAnchor.constraint(equalTo: (self.searchBarTopTags?.view.bottomAnchor)!, constant: -self.amountToShiftBy).isActive = true

And inside keyboardWillHide

self.searchBarTopTags?.myView.bottomAnchor.constraint(equalTo: (self.searchBarTopTags?.view.bottomAnchor)!, constant: 0).isActive = true

which off course will cause a conflict as the keyboard hides/shows , you need to create the bottom constraint only once say in viewDidLoad , then play with the constant value inside those methods , like this

var bottomConstraint:NSLayoutConstraint!

//

bottomConstraint = self.searchBarTopTags?.myView.bottomAnchor.constraint(equalTo: (self.searchBarTopTags?.view.bottomAnchor)!, constant: 0)
bottomConstraint.isActive = true

//

@objc func keyboardWillShow(notification: NSNotification) {

   // other code
   bottomConstraint.constant = -self.amountToShiftBy
}

@objc func keyboardWillHide(notification: NSNotification) {

   bottomConstraint.constant = 0 
   // other code
}

Answer 2

Each time you call the following line, a new constraint will be added:

self.searchBarTopTags?.myView.bottomAnchor.constraint(equalTo: (self.searchBarTopTags?.view.bottomAnchor)!, constant: -self.amountToShiftBy).isActive = true

You need to add a reference to the constraint and just change its constant.

let constraint = self.searchBarTopTags?.myView.bottomAnchor.constraint...
contraint.constant = ...