Swift数组追加不适用于collectionView重新加载数据

Posted 2023-03-14

【中文标题】Swift数组追加不适用于collectionView重新加载数据

【英文标题】：Swift array append not working on collectionView reload data

【发布时间】：2018-08-03 13:08:41

【问题描述】：

在我的 collectionView 单元格中，我有一个嵌套的集合视图。它在进行 api 调用 (didSet) 后首先更新，但是当我尝试将数据附加到数据源数组并重新加载 collectionView 时，在加载更多机制中。更改不会反映。这是我的代码

class PhotosCollectionViewController:    

   UICollectionViewCell,UICollectionViewDelegate,
   UICollectionViewDataSource, UICollectionViewDelegateFlowLayout 


let network = networkingService()
let keychain = KeychainSwift()

var userID: String?
var code: String?

 var platesID: String!

    didSet

         let parameters: Parameters = ["code": code!, "userID": userID!, 
  "plateID": platesID!]

        network.makeGetRequestDecodable(parameters: parameters, url: 
         "endpoint")  (reponse) in


            do 


                let modeled = try JSONDecoder().decode([gps_sing].self, from:reponse)

                self.gps_singleton_posts = modeled
                print("Reload Method Called")
                self.appsCollectionView?.reloadData()


             catch let err 
                print(err)
            


        


    


 var gps_singleton_posts: [gps_sing]?
let gridId = "gridID"
var appsCollectionView: UICollectionView? = 

    let layout = UICollectionViewFlowLayout()
    layout.minimumInteritemSpacing = 0
    layout.minimumLineSpacing = 3


    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
    collectionView.backgroundColor = UIColor.white

    collectionView.translatesAutoresizingMaskIntoConstraints = false
    return collectionView

()

override init(frame: CGRect) 

    super.init(frame: frame)





    if let value = keychain.get("userID") 
        self.userID = value
        // print("keychain\(self.userID!)")
    
    if let value = keychain.get("security_token") 
        self.code = value
        // print("keychain\(self.code!)")
    


    appsCollectionView?.dataSource = self
    appsCollectionView?.delegate = self
    appsCollectionView?.contentInset = UIEdgeInsetsMake(60, 0, 0, 0)
     appsCollectionView?.scrollIndicatorInsets =  UIEdgeInsetsMake(60, 
     0, 0, 0)

    addSubview(appsCollectionView!);


    addConstraintsWithFormat("H:|[v0]|", views: appsCollectionView!)
    addConstraintsWithFormat("V:|[v0]|", views: appsCollectionView!)
    appsCollectionView?.register(ImageCell.self, 
    forCellWithReuseIdentifier: gridId)


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




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

    return CGSize(width: 123, height: 123)



func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int 

    print(gps_singleton_posts)
    if let count = gps_singleton_posts?.count

        return count
    

    return 0

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 


let parameters: Parameters = ["code": code!, "userID": userID!, 
"plateID": platesID!,"token":"loadScroll","lim":gps_singleton_posts! 
[(gps_singleton_posts!.count)-1].id!]


  network.makeGetRequestDecodable(parameters: parameters, url: "get/getGridPS.php")  (reponse) in


        do 


            let modeled = try JSONDecoder().decode([gps_sing].self, from:reponse)

            for model in modeled
                self.gps_singleton_posts?.append(model)
            
           print("Reload Method Called")
            collectionView.reloadData()
            print(self.gps_singleton_posts)

         catch let err 
            print(err)
         
    

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

    print(self.gps_singleton_posts?.count)

    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: gridId, for: indexPath)
        as! ImageCell

    cell.backgroundColor = UIColor.red
    cell.singlePost = gps_singleton_posts![indexPath.row]

    return cell


func scrollViewDidScroll(_ scrollView: UIScrollView) 


    scrollView.isScrollEnabled = false



 


 class ImageCell: UICollectionViewCell 


var imageViewGrid: UIImageView = 
    let imageView = UIImageView()
    imageView.contentMode = .scaleAspectFill
    imageView.frame = CGRect(x: 0, y:0 , width: 100, height: 100)
    imageView.image = UIImage(named: "delete")
    imageView.clipsToBounds = true
    imageView.translatesAutoresizingMaskIntoConstraints = false
    return imageView
()

var textLabel: UILabel = 

    let lv = UILabel()
    lv.textColor = UIColor.red
    lv.translatesAutoresizingMaskIntoConstraints = false
    return lv
()

var singlePost: gps_sing! 

    didSet

        let imageUrl = singlePost.uid
        print(imageUrl!)

        imageViewGrid.setImageWith(NSURL(string: imageUrl!)! as URL)


    



override init(frame: CGRect) 
    super.init(frame: frame)
    setUpViews()


func setUpViews()

    addSubview(imageViewGrid)
    addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "H:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": imageViewGrid]))


    addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": imageViewGrid]))



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

在上面的代码中 (didSelectAt) 函数用于加载更多的项目..但没有反映更改。请帮帮我。非常感谢您回答我的问题。

【参考方案1】：

所以，我找到了解决问题的方法。在上面的集合视图中，我禁用了滚动..因为重新加载数据后添加的内容没有显示出来。一旦我启用滚动数据开始显示。

【参考方案2】：

首先：切勿在并行线程中更改布局。

我在 platesID 的didSet 中看到您正在执行 API 调用，并且在其响应中您正在尝试重新加载集合视图。这种操作必须在主线程中完成！尝试用这种方式包装collectionview.reloadData()

DispatchQueue.main.async  [weak self] in
    self?.appsCollectionView?.reloadData()

我不知道这是否能解决您的所有问题，但 reloadData() 操作可能无法在辅助线程中正常工作。

布局操作必须始终在主线程上启动。

【讨论】：

您好，感谢您的回答！将尝试并回复您

刚刚试了一下...没用 :( 还有什么我能做的吗？