UICollectionView无法正确滚动

Question

我正在填充一个UICollectionView，其中的单元格为全屏，并且它们水平滚动。正确的数据显示在屏幕上，但是当我按我的按钮打印出当前价格时，它将继续打印下一个indexPath的价格。我认为我在滚动时做错了什么。如果分页启用是打开还是关闭，也没有任何区别。

   class PostCell: UICollectionViewCell {
let containerView:UIView = {
       let view = UIView()
       view.translatesAutoresizingMaskIntoConstraints = false
       view.clipsToBounds = true
       return view
   }()

let priceLabel:UILabel = {
         let label = UILabel()
         label.font = UIFont.boldSystemFont(ofSize: 20)
         label.text = "price"
         label.textColor = .black
         label.translatesAutoresizingMaskIntoConstraints = false
         return label
     }()
let myButton: UIButton = {
    let button = UIButton(type: .system)
    button.titleLabel?.font = UIFont.systemFont(ofSize: 18)
    button.backgroundColor =  .red 
    return button

}()
func set(name: String, brand: String, price: String){
       priceLabel.text = price

   }
  override init(frame: CGRect) {
     super.init(frame: frame)
    self.contentView.addSubview(containerView)
    containerView.addSubview(priceLabel)
    containerView.addSubview(myButton)
    setupCellConstraints()
    }
     private func setupCellConstraints(){

       containerView.anchor(top: contentView.topAnchor, left: contentView.leftAnchor, bottom: contentView.bottomAnchor, right: contentView.rightAnchor, paddingTop: 0, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)

       nameLabel.anchor(top: containerView.topAnchor, left: nil, bottom: nil, right: nil, paddingTop: 50, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
    brandLabel.anchor(top: nameLabel.bottomAnchor, left: nil, bottom: nil, right: nil, paddingTop: 50, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
    priceLabel.anchor(top: brandLabel.bottomAnchor, left: nil, bottom: nil, right: nil, paddingTop: 50, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 0, height: 0)
    myButton.anchor(top: priceLabel.bottomAnchor, left: nil, bottom: nil, right: nil, paddingTop: 60, paddingLeft: 0, paddingBottom: 0, paddingRight: 0, width: 70, height: 70)

   }
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}



   class CollectionViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {

 let cellId = "cellId"
 var itemsArr = [Item]()
     init() {
       super.init(collectionViewLayout: UICollectionViewFlowLayout())
   }
   required init?(coder: NSCoder) {
       fatalError("init(coder:) has not been implemented")
   }

  private var collectionViewFlowLayout: UICollectionViewFlowLayout {
    return collectionViewLayout as! UICollectionViewFlowLayout
}
override func viewDidLoad() {
    parseData()
    collectionView.showsHorizontalScrollIndicator = false
    collectionView.showsVerticalScrollIndicator = false
    collectionViewFlowLayout.minimumLineSpacing = 0
    self.collectionView.isPagingEnabled = true
    if let layout = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {
        layout.scrollDirection = .horizontal
    }

    collectionView?.register(PostCell.self, forCellWithReuseIdentifier: cellId)

} 

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

    return CGSize(width: view.frame.width, height: view.frame.height)
   }

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

@objc func buttonPressed(){
    print(price)
}

var price: String = ""
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

      let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! PostCell
    let item = itemsArr[indexPath.row]]
    price = item.price
    cell.set(name: item.name, brand: item.brand, price: item.price)
    cell.myButton.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside)
      print(item)
      return cell
  }

Answer 1

原因：

这是因为每当创建或重新使用新的cellForItemAt时都会多次调用cell。因此，在price值中保存的CollectionViewController将用于最近为其调用cell的cellForItemAt。

解决方案：

而不是将price值保存在CollectionViewController中，然后打印出来，请使用closure来获取特定price的cell确切值。

在PostCell中，创建一个handler并以设置为buttonPressed()的target的myButton方法调用，即

class PostCell: UICollectionViewCell {
    //rest of the code...

    var handler: ((String?)->())? //here....

    let myButton: UIButton = {
        let button = UIButton(type: .system)
        button.titleLabel?.font = UIFont.systemFont(ofSize: 18)
        button.backgroundColor =  .red
        button.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside) //here....
        return button
    }()

    @objc func buttonPressed(){
        handler?(priceLabel.text) //here....
    }
}

现在，在collectionView(_:cellForItemAt:)中将handler设置为cell，即

override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! PostCell
    let item = itemsArr[indexPath.row]
    cell.set(name: item.name, brand: item.brand, price: item.price)
    cell.handler = {(price) in //here....
        print(price)
    }
    return cell
}

Answer 2

这是给您的另一个建议；

// we capture the tag of the button and tag points the index of array.
@objc func buttonPressed(_ sender : UIButton){
    let item = itemArr[sender.tag]
    print(item)
}

var price: String = ""
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! PostCell
    let item = itemsArr[indexPath.row]]
    price = item.price
    cell.set(name: item.name, brand: item.brand, price: item.price)
    cell.myButton.tag = indexPath.row // added that line.
    cell.myButton.addTarget(self, action: #selector(buttonPressed(:)), for: .touchUpInside) // changed that line little bit.
    print(item)
    return cell
}