我有一个包含uicollectionview的视图控制器。每个collectionview单元均包含一个按钮，单击该按钮可在该单元中添加一个新标签。为了扩大每个单元格的高度，我称reloadItems(at: [indexPath])。
[不幸的是，调用reloadItems(at: [indexPath])会淡出旧标签并淡入新标签，如何防止任何标签褪色？
每当我单击addLabel按钮时，该错误就会更加明显：一个新标签淡入，但是以前不可见的标签突然又出现了，而以前可见的任何标签又变魔术了。
reloadItems(at: [indexPath])似乎以不同的方式切换了每个新标签的字母。我想调整大小并将新标签添加到单元中，而不会丢失任何标签。
这是我的代码：
ViewController
class ViewController: UIViewController {
weak var collectionView: UICollectionView!
var expandedCellIdentifier = "ExpandableCell"
var cellWidth:CGFloat{
return collectionView.frame.size.width
}
var expandedHeight : CGFloat = 200
var notExpandedHeight : CGFloat = 50
//the first Int gives the row, the second Int gives the amount of labels in the row
var isExpanded = [Int:Int]()
override func viewDidLoad() {
super.viewDidLoad()
for i in 0..<4 {
isExpanded[i] = 1
}
}
}
extension ViewController:UICollectionViewDataSource{
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return isExpanded.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: expandedCellIdentifier, for: indexPath) as! ExpandableCell
cell.indexPath = indexPath
cell.delegate = self
cell.setupCell = "true"
return cell
}
}
extension ViewController:UICollectionViewDelegateFlowLayout{
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
if isExpanded[indexPath.row]! > 1{
let height = (collectionView.frame.width/10)
let newHeight = height * CGFloat(isExpanded[indexPath.row]!)
return CGSize(width: cellWidth, height: newHeight)
}else{
return CGSize(width: cellWidth, height: collectionView.frame.width/6 )
}
}
}
extension ViewController:ExpandedCellDeleg{
func topButtonTouched(indexPath: IndexPath) {
isExpanded[indexPath.row] = isExpanded[indexPath.row]! + 1
UIView.animate(withDuration: 0.8, delay: 0.0, usingSpringWithDamping: 0.9, initialSpringVelocity: 0.9, options: UIView.AnimationOptions.curveEaseInOut, animations: {
self.collectionView.reloadItems(at: [indexPath])
}, completion: { success in
print("success")
})
}
}
协议
protocol ExpandedCellDeleg:NSObjectProtocol{
func topButtonTouched(indexPath:IndexPath)
}
ExpandableCell
class ExpandableCell: UICollectionViewCell {
weak var delegate:ExpandedCellDeleg?
public var amountOfIntervals:Int = 1
public var indexPath:IndexPath!
var setupCell: String? {
didSet {
print("cell should be setup!!")
}
}
let ivAddLabel: UIImageView = {
let imageView = UIImageView()
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.image = #imageLiteral(resourceName: "plus")
imageView.tintColor = .black
imageView.contentMode = .scaleToFill
imageView.backgroundColor = UIColor.clear
return imageView
}()
override init(frame: CGRect) {
super.init(frame: .zero)
contentView.addSubview(ivAddLabel)
let name = UILabel(frame: CGRect(x: 0, y: 0, width: 100, height: 18))
name.center = CGPoint(x: Int(frame.width)/2 , y: 20)
name.textAlignment = .center
name.font = UIFont.systemFont(ofSize: 16)
name.textColor = UIColor.black
name.text = "Fred"
contentView.addSubview(name)
ivAddLabel.rightAnchor.constraint(equalTo: self.rightAnchor, constant: -14).isActive = true
ivAddLabel.topAnchor.constraint(equalTo: self.topAnchor, constant: 10).isActive = true
ivAddLabel.widthAnchor.constraint(equalToConstant: 20).isActive = true
ivAddLabel.heightAnchor.constraint(equalToConstant: 20).isActive = true
ivAddLabel.layer.masksToBounds = true
ivAddLabel.isUserInteractionEnabled = true
let addGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(ivAddLabelSelected))
ivAddLabel.addGestureRecognizer(addGestureRecognizer)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
@objc func ivAddLabelSelected(){
print("add button was tapped!")
if let delegate = self.delegate{
amountOfIntervals = amountOfIntervals + 1
let height = (20*amountOfIntervals)
let name = UILabel(frame: CGRect(x: 0, y: 0, width: 100, height: 18))
name.center = CGPoint(x: Int(frame.width)/2, y: height)
name.textAlignment = .center
name.font = UIFont.systemFont(ofSize: 16)
name.textColor = UIColor.black
name.text = "newFred"
name.alpha = 0.0
contentView.addSubview(name)
UIView.animate(withDuration: 0.2, animations: { name.alpha = 1.0 })
delegate.topButtonTouched(indexPath: indexPath)
}
}
}
[建议您阅读自定义大小的UICollectionViewCells（例如UICollectionView Self Sizing Cells with Auto Layout）和UIStackView（例如https://janthielemann.de/ios-development/self-sizing-uicollectionviewcells-ios-10-swift-3/）。
您应该使用UIStackView，并限制单元格contentView的顶部和底部边缘。然后，您可以将Labels作为managedSubviews添加到stackView中。这将为标签添加动画。使用自动调整大小的单元，您无需reloadItems，它应会按预期工作。
是因为您为新标签设置了动画
UIView.animate(withDuration: 0.2, animations: { name.alpha = 1.0 })
并并行地重新加载创建新单元格的单元格/重复使用现有单元格并显示它，但同时您也将重新包装到动画块中，这看起来很奇怪而且没用：
UIView.animate(withDuration: 0.8, delay: 0.0, usingSpringWithDamping: 0.9, initialSpringVelocity: 0.9, options: UIView.AnimationOptions.curveEaseInOut, animations: {
self.collectionView.reloadItems(at: [indexPath])
}, completion: { success in
print("success")
})
您需要删除两个动画，然后重新加载单元格。如果您需要一个漂亮的单元扩展动画，则需要实现集合布局，该布局将处理所有状态-动画的开始，中间，结束。这个很难（硬。
如果无法解决问题，请尝试使用其他答案“具有自动布局的UICollectionView自动调整大小的单元格”中的建议，然后忘记动画的想法或实现自定义布局。