Collectionview在NavigationBar下不隐藏

collectionView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
    collectionView.topAnchor.constraint(equalTo: view.topAnchor),
    collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
    collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
    collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor)
])

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    collectionView.isHidden = false // 或者根据需要设置为 true 来隐藏
}

class MyViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
    
    var collectionView: UICollectionView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let layout = UICollectionViewFlowLayout()
        collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "cell")
        
        view.addSubview(collectionView)
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            collectionView.topAnchor.constraint(equalTo: view.topAnchor),
            collectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            collectionView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            collectionView.trailingAnchor.constraint(equalTo: view.trailingAnchor)
        ])
    }
    
    // UICollectionViewDataSource methods...
}