swift - 将图像添加到 UICollection header Swift

Question

我希望在 Collection View 的 header 中实现图像。这是我到目前为止的代码，但在我测试时没有出现标题。我错过了什么吗？

    func collectionView(_ collectionView: UICollectionView, viewForHeaderInSection section: Int) -> UIView? {
    let view = UIView()
    let image = UIImageView()
    image.frame = CGRect(x: collectionView.frame.width - 10 , y: 0, width: 20, height: 20)
    image.image = UIImage.init(named: "trophyCase")
    view.addSubview(image)
    return view
}

Answer 1

UICollectionViewDelegate 不提供像 viewForHeaderInSection 这样的方法

相反，您可以使用 UICollectionViewDataSource 的 viewForSupplementaryElementOfKind 方法

func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
    guard kind == UICollectionView.elementKindSectionHeader else {
        fatalError("Unrecognized element of kind: \(kind)")
    }

    let view: ReusableHeaderView = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: kind, for: indexPath) as! ReusableHeaderView
    view.imageView.image = UIImage.init(named: "trophyCase")
    view.imageView.frame = CGRect(x: collectionView.frame.width - 10 , y: 0, width: 20, height: 20)
    return view
}

您还需要注册 elementKindSectionHeader

collectionView.register(ReusableHeaderView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: UICollectionView.elementKindSectionHeader)

以下是您的ReusableHeaderView

class ReusableHeaderView: UICollectionReusableView {
    let imageView = UIImageView()

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.setupUI()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.setupUI()
    }

    private func setupUI() {
        self.addSubview(imageView)

        // Instead of settings imageView.frame, add following to use autolayout constraints
        self.imageView.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            imageView.topAnchor.constraint(equalTo: self.topAnchor),
            imageView.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -10.0),
            imageView.widthAnchor.constraint(equalToConstant: 20.0),
            imageView.heightAnchor.constraint(equalToConstant: 20.0)
        ])
    }

}