我正试图以编程方式创建UICollectionView。我需要在单元格内添加标签，因此我创建了CollectionViewCell类。
这是该类：
import UIKit
class MyCollectionViewCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
这是collectionView实现类：
import UIKit
class TwoViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, UICollectionViewDelegate {
let leftAndRightPaddings: CGFloat = 80.0
let numberOfItemsPerRow: CGFloat = 7.0
let screenSize: CGRect = UIScreen.main.bounds
private let cellReuseIdentifier = "collectionCell"
var items = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31"]
override func viewDidLoad() {
super.viewDidLoad()
let flowLayout = UICollectionViewFlowLayout()
let collectionView = UICollectionView(frame: self.view.bounds, collectionViewLayout: flowLayout)
collectionView.register(MyCollectionViewCell.self, forCellWithReuseIdentifier: cellReuseIdentifier)
collectionView.register(UICollectionViewCell.self, forCellWithReuseIdentifier: "collectionCell")
collectionView.delegate = self
collectionView.dataSource = self
collectionView.backgroundColor = UIColor.cyan
self.view.addSubview(collectionView)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int
{
return self.items.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellReuseIdentifier, for: indexPath) as! MyCollectionViewCell
cell.backgroundColor = UIColor.green
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize
{
let width = (screenSize.width-leftAndRightPaddings)/numberOfItemsPerRow
return CGSize(width: width, height: width)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets
{
return UIEdgeInsets(top: 20, left: 8, bottom: 5, right: 8)
}
}
当单元格被生成时，会出现错误：
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell
{
let cell = collectionView.dequeueReusableCellWithReuseIdentifier(cellReuseIdentifier, forIndexPath: indexPath) as! MyCollectionViewCell
错误原因是：
Could not cast value of type 'UICollectionViewCell' (0x1033cc820) to 'CollectionViewProgramatically.MyCollectionViewCell' (0x1015a4f88).
contentView属性（https://developer.apple.com/documentation/uikit/uicollectionviewcell）：为了配置单元格的外观，请将需要呈现数据项内容的视图作为子视图添加到`contentView`属性中的视图中。不要直接将子视图添加到单元格本身中。 - Yehor HromadskyiviewDidLayoutSubviews中设置你的集合视图，而不是在viewDidLoad中。请参见此处的讨论：https://stackoverflow.com/questions/49742156/programmatically-placing-collectionview-in-view?noredirect=1&lq=1 - Matt Bearsonrequired init?(coder aDecoder: NSCoder)中使用super.init(coder: aDecoder)才能使它在Swift 5中正常工作。如果其他人也遇到了这个问题，请注意。 - Mika Hämäläinen