UICollectionView中删除一个单元格后刷新单元格布局

Posted 2023-03-13

【中文标题】UICollectionView中删除一个单元格后刷新单元格布局

【英文标题】：Cell Layout refresh after deleting one cell in UICollectionView

【发布时间】：2017-11-11 07:41:00

【问题描述】：

我创建了一个 UICollectionView 动态调整单元格高度。 我正在像这样调整单元格的大小：

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize 
let approximatedwidthoftextview = view.frame.width - 70
let size = CGSize(width: approximatedwidthoftextview, height: 1000)
let attributes = [NSAttributedStringKey.font: UIFont(name: "Avenir Next", size: 18)]
let estimatedFrame = NSString(string: allnotes[indexPath.row].note).boundingRect(with: size, options: .usesLineFragmentOrigin, attributes: attributes, context: nil)
return CGSize(width: view.frame.width, height: estimatedFrame.height + 38)

当我删除一个单元格时，剩余单元格的布局会有点奇怪。内容被截断。

奇怪的是，导航到前一个视图控制器，然后返回到这个控制器修复了单元格布局，单元格恢复正常。

知道这里有什么问题吗？

import UIKit

private let reuseIdentifier = "Cell"

class AddedNotesCollectionViewController: UICollectionViewController, 
UICollectionViewDelegateFlowLayout 

var allnotes = [notesarray]()


override func viewDidAppear(_ animated: Bool) 

    print(allnotes.count)


override func viewDidLoad() 
    super.viewDidLoad()

    view.backgroundColor = UIColor(red:0.15, green:0.20, blue:0.22, alpha:1.0)
    // Uncomment the following line to preserve selection between presentations
    // self.clearsSelectionOnViewWillAppear = false

    // Register cell classes
    self.collectionView!.register(AddedNotesCollectionViewCell.self, forCellWithReuseIdentifier: reuseIdentifier)

    // Do any additional setup after loading the view.


override func didReceiveMemoryWarning() 
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.






override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int 
    // #warning Incomplete implementation, return the number of items
    return allnotes.count


override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) 
    var tag = indexPath.row
    print(tag)


override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell 
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath) as! AddedNotesCollectionViewCell

    // Configure the cell

    cell.deleteBtn.layer.setValue(indexPath.row, forKey: "index")
    cell.deleteBtn.addTarget(self, action: #selector(deleteUser(sender:)), for: UIControlEvents.touchUpInside)
    cell.backgroundColor = allnotes[indexPath.row].prioritycolor
    cell.textview.text = allnotes[indexPath.row].note

    // Remove the button from the first cell

    return cell

//deleting cell func

@objc func deleteUser(sender:UIButton) 
    let i : Int = (sender.layer.value(forKey: "index")) as! Int
    allnotes.remove(at: i)
    addedNotesArrayGlobal.addednotesarrays.remove(at: i)

    collectionView?.reloadData()





override func viewDidLayoutSubviews() 
    super.viewDidLayoutSubviews()
    collectionView?.collectionViewLayout.invalidateLayout()

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize 
    let approximatedwidthoftextview = view.frame.width - 70
    let size = CGSize(width: approximatedwidthoftextview, height: 1000)
    let attributes = [NSAttributedStringKey.font: UIFont(name: "Avenir Next", size: 18)]
    let estimatedFrame = NSString(string: allnotes[indexPath.row].note).boundingRect(with: size, options: .usesLineFragmentOrigin, attributes: attributes, context: nil)
    return CGSize(width: view.frame.width, height: estimatedFrame.height + 32)

【问题讨论】：

您需要在 viewDidLayoutSubviews() 中为布局更改编写代码。删除单元格后，该方法会自动调用，如果没有，则需要调用。

@Jacky 你能详细说明一下吗？你说的是哪个代码？？

@Jacky 对什么是“布局更改代码”感到困惑？无效布局（）？

您需要为集合视图布局编写代码。

@Jacky Proper 很困惑。这就是为什么-> 我正在更改“sizeforitematindexPath”中的单元格高度，仅此而已。你说的是哪个collectionViewLayout代码？

【参考方案1】：

尽管使用上述算法在collectionView 中动态调整大小效果很好，但它只是不完整。我切换到 UITableView 并使用自动布局进行动态调整大小。它简单、容易而且效果很好。