如何在不移动单元格的情况下为collectionView设置动画？

Question

我正在尝试创建一个collectionView，当用户向上滑动时该视图会向上滑动。现在，我使用按钮而不是滚动手势来触发动画。动画开始时，我希望collectionView的高度扩大，但单元格保持原样，然后随着用户滚动向上滑动。如何在不移动单元格的情况下为collectionView设置动画？这可能吗？我想让collectionView扩大并显示滚动过程中被掩盖的隐藏单元格而不显示，或者显示collectionView中的空白，而不仅仅是将屏幕上的所有单元格移高。

相关代码的功能

var buttonPressed:Bool = true
@IBAction func changeView(_ sender: Any) {
    if buttonPressed{
    UIView.animate(withDuration: 0.05){
        self.animateCollectionView.frame = CGRect(x: 0, y: 100, width: 600, height: 1000)
     //   self.animateCollectionView.transform = CGAffineTransform(translationX: 0, y: -20)
        self.view.sendSubview(toBack: self.animateCollectionView)
        self.buttonPressed = !self.buttonPressed
        print("Ive been expanded")
    }
    }
    else{
        UIView.animate(withDuration: 0.05){
            self.animateCollectionView.frame = CGRect(x: 0, y: 20, width: 600, height: 1000)
           // self.animateCollectionView.transform = CGAffineTransform(translationX: 0, y: 20)
            self.buttonPressed = !self.buttonPressed
        }
    }
}

整体代码：

import UIKit

class ViewController: UIViewController,UICollectionViewDataSource,UICollectionViewDelegate {

    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 200
    }

    var counter:Int = 0
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = self.animateCollectionView.dequeueReusableCell(withReuseIdentifier: "cell", for: indexPath) as! customCell
        counter+=1
        cell.cellLabel.text = "\(counter)"
        cell.backgroundColor = UIColor.orange
        return cell
    }


    @IBOutlet weak var animateCollectionView: UICollectionView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        animateCollectionView.dataSource = self
        animateCollectionView.delegate = self
        animateCollectionView.backgroundColor = UIColor.blue
        animateCollectionView.frame = CGRect(x: 0, y: 100, width: 600, height: 1000)
         self.view.sendSubview(toBack: self.animateCollectionView)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    var buttonPressed:Bool = true
    @IBAction func changeView(_ sender: Any) {
        if buttonPressed{
        UIView.animate(withDuration: 0.05){
            self.animateCollectionView.frame = CGRect(x: 0, y: 100, width: 600, height: 1000)
         //   self.animateCollectionView.transform = CGAffineTransform(translationX: 0, y: -20)
            self.view.sendSubview(toBack: self.animateCollectionView)
            self.buttonPressed = !self.buttonPressed
            print("Ive been expanded")
        }
        }
        else{
            UIView.animate(withDuration: 0.05){
                self.animateCollectionView.frame = CGRect(x: 0, y: 20, width: 600, height: 1000)
               // self.animateCollectionView.transform = CGAffineTransform(translationX: 0, y: 20)
                self.buttonPressed = !self.buttonPressed
            }
        }
    }

}

class customCell :UICollectionViewCell{
    @IBOutlet weak var cellLabel: UILabel!
}