ios - 为什么 UICollectionView 根本没有响应？

Question

我正在 ViewController 中设置一个 UICollectionView。但是，它不会响应任何用户交互，didSelectItemAt 函数未被调用，我无法滚动它。

我已经在 viewDidLoad() 中正确设置了 DataSource 和 Delegate。这是我的代码:

class WelcomeController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {

let padding: CGFloat = 30
var sources = [Source]()
let sourceCellId = "sourceCellId"

func fetchSources() {
    ApiSourceService.sharedInstance.fetchSources() { (root: Sources) in
        self.sources = root.source
        self.sourceCollectionView.reloadData()
    }
}

let backgroundImage: UIImageView = {
   let iv = UIImageView()
    iv.image = UIImage(named: "background")
    iv.contentMode = .scaleAspectFill
    iv.translatesAutoresizingMaskIntoConstraints = false
    iv.clipsToBounds = false
    return iv
}()

let overlayView: UIView = {
   let view = UIView()
    view.translatesAutoresizingMaskIntoConstraints = false
    view.backgroundColor = .white
    return view
}()

let logo: UIImageView = {
    let iv = UIImageView()
    iv.image = UIImage(named: "mylogo")
    iv.translatesAutoresizingMaskIntoConstraints = false
    iv.clipsToBounds = false
    return iv
}()

let defaultButton: UIButton = {
    let ub = UIButton()
    ub.translatesAutoresizingMaskIntoConstraints = false
    ub.setTitle("Inloggen met E-mail", for: .normal)
    ub.setImage(UIImage(named: "envelope"), for: .normal)
    ub.imageEdgeInsets = UIEdgeInsetsMake(15, 0, 15, 0)
    ub.imageView?.contentMode = .scaleAspectFit
    ub.contentHorizontalAlignment = .left
    ub.titleLabel?.font = UIFont.init(name: "Raleway-Regular", size: 16)
    ub.backgroundColor = .cuOrange
    return ub
}()

let continueWithoutButton: UIButton = {
    let ub = UIButton()
    ub.translatesAutoresizingMaskIntoConstraints = false

    let attributedString: NSMutableAttributedString = NSMutableAttributedString(string: "Doorgaan zonder in te loggen")
    let textRange = NSMakeRange(0, attributedString.length)
    attributedString.setColor(color: .cuOrange, forText: "Doorgaan")
    ub.setAttributedTitle(attributedString, for: .normal)

    ub.contentHorizontalAlignment = .center
    ub.titleLabel?.font = UIFont.init(name: "Raleway-Regular", size: 16)
    ub.titleLabel?.textColor = .white
    return ub
}()


let sourceCollectionView: UICollectionView = {
   let layout = UICollectionViewFlowLayout()
    let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
    cv.translatesAutoresizingMaskIntoConstraints = false
    cv.backgroundColor = .white
    return cv
}()



let termsButton: UIButton = {
    let ub = UIButton()
    ub.translatesAutoresizingMaskIntoConstraints = false

    let attributedString: NSMutableAttributedString = NSMutableAttributedString(string: "Met het maken van een account \nof bij inloggen, ga ik akkoord \nmet servicevoorwaarden.")
    let textRange = NSMakeRange(0, attributedString.length)
    attributedString.setColor(color: .cuOrange, forText: "servicevoorwaarden")
    ub.setAttributedTitle(attributedString, for: .normal)

    ub.contentHorizontalAlignment = .center
    ub.contentVerticalAlignment = .bottom
    ub.titleLabel?.lineBreakMode = .byWordWrapping
    ub.titleLabel?.font = UIFont.init(name: "Raleway-Regular", size: 14)
    ub.titleLabel?.textColor = .white
    ub.titleLabel?.textAlignment = .center
    return ub
}()

override func viewDidLoad() {
    super.viewDidLoad()

    fetchSources()

    sourceCollectionView.dataSource = self
    sourceCollectionView.delegate = self
    sourceCollectionView.register(SourceCell.self, forCellWithReuseIdentifier: sourceCellId)

    view.addSubview(backgroundImage)
    view.addSubview(overlayView)
    backgroundImage.addSubview(termsButton)
    backgroundImage.addSubview(logo)
    backgroundImage.addSubview(sourceCollectionView)

    backgroundImage.widthAnchor.constraint(lessThanOrEqualToConstant: 375).isActive = true
    backgroundImage.heightAnchor.constraint(lessThanOrEqualToConstant: 667).isActive = true
    backgroundImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    backgroundImage.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true



    logo.centerXAnchor.constraint(equalTo: backgroundImage.centerXAnchor).isActive = true
    logo.topAnchor.constraint(equalTo: backgroundImage.topAnchor, constant: padding).isActive = true
    logo.widthAnchor.constraint(equalToConstant: 107).isActive = true
    logo.heightAnchor.constraint(equalToConstant: 100).isActive = true

    sourceCollectionView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    sourceCollectionView.widthAnchor.constraint(equalTo: view.widthAnchor, constant: -(padding*1.5)).isActive = true
    sourceCollectionView.topAnchor.constraint(equalTo: logo.bottomAnchor, constant: padding).isActive = true
    sourceCollectionView.bottomAnchor.constraint(equalTo: termsButton.topAnchor, constant: -(padding*2)).isActive = true

    termsButton.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -padding).isActive = true
    termsButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    termsButton.widthAnchor.constraint(equalTo: view.widthAnchor, constant: -(padding*2)).isActive = true
    termsButton.heightAnchor.constraint(equalToConstant: 40).isActive = true

    sourceCollectionView.reloadData()

}

@objc func closeWelcomeController() {

    let appDelegate = UIApplication.shared.delegate as! AppDelegate
    appDelegate.switchViewControllers()

    self.dismiss(animated: true, completion: {

    })

}


func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

    let width = self.sourceCollectionView.frame.width
    let height = CGFloat(50)

    return CGSize(width: width, height: height)

}

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

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    print(sources[indexPath.item].feed_name)

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: sourceCellId, for: indexPath) as! SourceCell
    cell.preservesSuperviewLayoutMargins = true
    cell.source = sources[indexPath.item]

    return cell

}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    print("selecting")
}}

有人知道我在这里做错了什么吗？

我希望代码中不只是一个“愚蠢”的错误导致它不起作用，但在过去的几个小时里它一直在折磨我。

Answer 1

在 backgroundImage 即 UIImageView 中添加 sourceCollectionView 作为 subview 似乎不合适!从逻辑上讲， ImageView 不代表容器 View (例如 UIView UIStackView、UIScrollView)，即即使代码允许您这样做，它仍然不明智；此外，即使向 ImageView 添加 subview 是可以的(不是)，默认情况下 ImageView 是禁用用户交互的(userInteractionEnabled 默认为 false ImageView )，这就是为什么您甚至无法滚动 Collection View ，它是禁用的用户交互组件的一部分( subview )。

在您的 viewDidLoad() 中，您正在实现:

backgroundImage.addSubview(termsButton)
backgroundImage.addSubview(logo)
backgroundImage.addSubview(sourceCollectionView)

不要这样做，而是将它们添加到 View Controller 的主视图中:

view.addSubview(termsButton)
view.addSubview(logo)
view.addSubview(sourceCollectionView)

为了检查是否是问题的原因，至少对 Collection View (view.addSubview(sourceCollectionView)) 执行此操作。

为了组织 View 的层次结构(一个在另一个之上)，您可以同时使用:bringSubview(toFront:)或 sendSubview(toBack:) .例如，将 Collection View 添加到 view 之后，您可能需要:

view.bringSubview(toFront: sourceCollectionView)

确保 Collection View 位于所有组件之上。