有一个大问题我几天都解决不了。
我有一个带UICollectionView的UIViewController，其中有3个单元格具有不同的内容。这是我的课：
class PostView: AppViewAddMenu, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {
var homeController: FeedController?
var contentArray = [PostContentModel]()
var postInfo: PostModel?
lazy var collectionView: UICollectionView = {
let layout = UICollectionViewFlowLayout()
layout.minimumLineSpacing = 3
let cv = UICollectionView(frame: .zero, collectionViewLayout: layout)
cv.delegate = self
cv.dataSource = self
cv.backgroundColor = .white
return cv
}()
override func setupViewController() {
collectionView.register(PostViewCell.self, forCellWithReuseIdentifier: "cellId")
view.addSubview(collectionView)
view.addConstraintsWithFormat("H:|[v0]|", views: collectionView)
view.addConstraintsWithFormat("V:|-60-[v0]|", views: collectionView)
fetchPost(id: postInfo?.id)
}
func fetchPost(id: Int?){
guard let ID = id else {
print("ID faild")
return
}
let url: String = "https://FTP.ru/wp-json/mobileApi/v1/post/\(ID)"
ApiService.sharedInstance.fetchContent(url: url, completion: { (Posts: [PostContentModel]) in
self.contentArray = Posts
self.collectionView.reloadData()
})
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 2
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellId", for: indexPath) as! PostViewCell
cell.contentArray = contentArray
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: view.frame.width, height: 1000)
}
}
第一个单元格的想法是从如下站点获取json：
[switch, content]。从UICollectionViewCell中的开关值调用不同的函数，这些函数通过addSubview ()在UICollectionViewCell中添加元素。代码如下：class PostViewCell: UICollectionViewCell {
override init(frame: CGRect) {
super.init(frame: frame)
backgroundColor = .white
anchor = self.topAnchor
}
var anchor: NSLayoutYAxisAnchor?
var contentArray: [PostContentModel]?{
didSet{
for number in contentArray! {
if(number.switcher == 1) {
anchor = addTextContent(content: number.content!, bottomAnchor: anchor!)
}
if(number.switcher == 2){
anchor = addImageContent(content: number.content!, bottomAnchor: anchor!)
}
if(number.switcher == 3){
anchor = addCaptionFirst(content: number.content!, bottomAnchor: anchor!)
}
if(number.switcher == 4){
anchor = addButtonLink(content: number.content!, link: number.link!, bottomAnchor: anchor!)
}
}
}
}
func addTextContent(content: String, bottomAnchor: NSLayoutYAxisAnchor) -> NSLayoutYAxisAnchor{
let shortContentPost: UILabel = {
let label = UILabel()
label.text = content
label.numberOfLines = 0
label.font = UIFont.systemFont(ofSize: 16, weight: UIFont.Weight.regular)
return label
}()
addSubview(shortContentPost)
shortContentPost.anchor(bottomAnchor, left: self.leftAnchor, bottom: nil, right: self.rightAnchor, topConstant: 15, leftConstant: 15, bottomConstant: 0, rightConstant: 15, widthConstant: 0, heightConstant: 0)
return shortContentPost.bottomAnchor
}
func addImageContent(content: String, bottomAnchor: NSLayoutYAxisAnchor) -> NSLayoutYAxisAnchor {
let image: CustomImageView = {
let image = CustomImageView()
image.image = UIImage(named: content)
image.contentMode = .scaleAspectFill
image.clipsToBounds = true
return image
}()
let imageURL = "https://brodude.ru/wp-content/uploads/" + content.addingPercentEncoding(withAllowedCharacters: .urlHostAllowed)!
image.loadImageUsingUrlString(urlString: imageURL)
addSubview(image)
image.anchor(bottomAnchor, left: self.leftAnchor, bottom: nil, right: self.rightAnchor, topConstant: 15, leftConstant: 0, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 250)
return image.bottomAnchor
}
func addCaptionFirst(content: String, bottomAnchor: NSLayoutYAxisAnchor) -> NSLayoutYAxisAnchor {
let Caption: UILabel = {
let lb = UILabel()
lb.text = content
lb.numberOfLines = 0
lb.font = UIFont.systemFont(ofSize: 20, weight: UIFont.Weight.semibold)
return lb
}()
addSubview(Caption)
Caption.anchor(bottomAnchor, left: self.leftAnchor, bottom: nil, right: self.rightAnchor, topConstant: 30, leftConstant: 15, bottomConstant: 0, rightConstant: 15, widthConstant: 0, heightConstant: 0)
return Caption.bottomAnchor
}
func addButtonLink(content: String, link: String, bottomAnchor: NSLayoutYAxisAnchor) -> NSLayoutYAxisAnchor {
let button: LinkButton = {
let bt = LinkButton()
bt.LinkString = link
bt.titleLabel?.font = UIFont.systemFont(ofSize: 18, weight: UIFont.Weight.semibold)
bt.setTitle(content, for: UIControlState.normal)
bt.sizeToFit()
bt.titleLabel?.numberOfLines = 0
bt.contentHorizontalAlignment = .left
bt.setTitleColor(UIColor(red: 0.07, green: 0.32, blue: 0.89, alpha: 1.0), for: UIControlState.normal)
bt.addTarget(self, action: #selector(linkOut), for: .touchUpInside)
return bt
}()
addSubview(button)
button.anchor(bottomAnchor, left: self.leftAnchor, bottom: nil, right: self.rightAnchor, topConstant: 20, leftConstant: 15, bottomConstant: 0, rightConstant: 15, widthConstant: 0, heightConstant: 0)
return button.bottomAnchor
}
该算法运行良好，但问题从更新单元开始。滚动时，使用
collectionView.reloadData ()。新的子视图分层在过去，文本变得更胖和堵塞的设备内存。这个过程无限期地继续，直到出现错误为止。一个问题的例子：，
对不起我的英语。
最佳答案
首先，不要：
addSubview(shortContentPost)
使用：
contentView.addSubview(shortContentPost)
对添加的所有子视图执行此操作。
contentView应该保存您的内容。在你的单元中实现这个
prepareForReuse：override func prepareForReuse() {
super.prepareForReuse()
let subviews = contentView.subviews
for subview in subviews {
subview.removeFromSuperview()
}
}
这将在重用单元格之前清除单元格内容。
尽管我强烈建议不要动态添加这些子视图，因为这样会丢失很多重用机制。默认情况下，我会将所有视图（标签/图像视图）添加到单元格中，然后使用它们的
isHidden属性根据内容隐藏/取消隐藏它们（例如，如果应该显示图像，请将所有其他视图的isHidden设置为true）。对于重用来说，这将是一个性能更好的选择，因为这样一来，每次重用单元格时都不必重新创建UI对象，只需重新配置labels/imageViews的内容即可。