滚动浏览集合视图后，为什么视图会消失？

Question

我正在尝试创建一个在键盘出现时向上滑动的视图，并且在此视图中是一个文本字段，用作搜索栏和集合视图以保存搜索结果。视图在键盘上方滑动得很好，但是一旦我点击其中一个单元格进行曲面滚动，视图就会消失。可能导致这种情况的原因。

我认为可能导致问题的代码

var offsetY:CGFloat = 0

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardFrameChangeNotification(notification:)), name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
}



@objc func keyboardFrameChangeNotification(notification: Notification) {
    if let userInfo = notification.userInfo {
        let endFrame = userInfo[UIKeyboardFrameEndUserInfoKey] as? CGRect
        let animationDuration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Double ?? 0
        let animationCurveRawValue = (userInfo[UIKeyboardAnimationCurveUserInfoKey] as? Int) ?? Int(UIViewAnimationOptions.curveEaseInOut.rawValue)
       let animationCurve = UIViewAnimationOptions(rawValue: Int(animationCurveRawValue))
        if let _ = endFrame, endFrame!.intersects(self.myView.frame) {
            self.offsetY = self.myView.frame.maxY - endFrame!.minY
            UIView.animate(withDuration: animationDuration, delay: TimeInterval(0), options: animationCurve, animations: {
                self.myView.frame.origin.y = self.myView.frame.origin.y - self.offsetY
            }, completion: nil)
        } else {
            if self.offsetY != 0 {
                UIView.animate(withDuration: animationDuration, delay: TimeInterval(0), options: animationCurve, animations: {
                    self.myView.frame.origin.y = self.myView.frame.origin.y + self.offsetY
                    self.offsetY = 0
                }, completion: nil)
            }
        }
    }
}

代码完整

import UIKit

class SearchCollectionViewController: UIViewController,UICollectionViewDelegate,UICollectionViewDelegateFlowLayout, UITextFieldDelegate, UICollectionViewDataSource {

@IBOutlet weak var searchBar: UITextField!
@IBOutlet weak var collectionView: UICollectionView!

@IBOutlet weak var myView: UIView!


var genericArray:[String] = ["A","B","C","D","E","F","G","Ab","Abc"]
var currentGenericArray:[String] = [String]()

override func viewDidLoad() {
    super.viewDidLoad()
    collectionView.delegate = self
    collectionView.dataSource = self
    let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
    layout.sectionInset = UIEdgeInsets(top: 0, left: 0, bottom: 10, right: 0)
    layout.itemSize = CGSize(width: (UIScreen.main.bounds.width-1)/2, height: (UIScreen.main.bounds.width-1)/2)
    layout.minimumInteritemSpacing = 1
    layout.minimumLineSpacing = 1
    layout.scrollDirection = .horizontal
    self.collectionView.collectionViewLayout = layout


    searchBar.delegate = self
    currentGenericArray = genericArray
    searchBar.addTarget(self, action: #selector(TableSearchViewController.textFieldDidChange), for: .editingChanged)



}

@objc func textFieldDidChange(){
    guard(!(searchBar.text?.isEmpty)!) else{
        currentGenericArray = genericArray
        collectionView.reloadData()
        return
    }
    currentGenericArray = genericArray.filter({letter -> Bool in
        letter.lowercased().contains(searchBar.text!)
    })
    collectionView.reloadData()
}


func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 1
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return currentGenericArray.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "collectionViewCell", for: indexPath) as! CollectionCell

    cell.collectionLabel.text = currentGenericArray[indexPath.row]

    return cell
}

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
    return 0
}

var offsetY:CGFloat = 0

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    NotificationCenter.default.addObserver(self, selector: #selector(ViewController.keyboardFrameChangeNotification(notification:)), name: NSNotification.Name.UIKeyboardWillChangeFrame, object: nil)
}



@objc func keyboardFrameChangeNotification(notification: Notification) {
    if let userInfo = notification.userInfo {
        let endFrame = userInfo[UIKeyboardFrameEndUserInfoKey] as? CGRect
        let animationDuration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Double ?? 0
        let animationCurveRawValue = (userInfo[UIKeyboardAnimationCurveUserInfoKey] as? Int) ?? Int(UIViewAnimationOptions.curveEaseInOut.rawValue)
        let animationCurve = UIViewAnimationOptions(rawValue: UInt(animationCurveRawValue))
        if let _ = endFrame, endFrame!.intersects(self.myView.frame) {
            self.offsetY = self.myView.frame.maxY - endFrame!.minY
            UIView.animate(withDuration: animationDuration, delay: TimeInterval(0), options: animationCurve, animations: {
                self.myView.frame.origin.y = self.myView.frame.origin.y - self.offsetY
            }, completion: nil)
        } else {
            if self.offsetY != 0 {
                UIView.animate(withDuration: animationDuration, delay: TimeInterval(0), options: animationCurve, animations: {
                    self.myView.frame.origin.y = self.myView.frame.origin.y + self.offsetY
                    self.offsetY = 0
                }, completion: nil)
            }
        }
    }
}

}


class CollectionCell:UICollectionViewCell{

@IBOutlet weak var collectionLabel: UILabel!

override func awakeFromNib() {
    collectionLabel.textAlignment = .center

}
}