Cell Layout refresh after deleting one cell in UIC

问题:

I created a UICollectionView with dynamic resizing of cell height. I am resizing the cell like this:

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)

}

When I delete one cell, the remaining cell’s layout get a bit strange. The content gets cut off.

Strangely enough, navigating to a previous viewcontroller and then coming back to this controller fixes the cell layout and cells go back to normal.

Any idea what’s wrong here?

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)
}

}

回答1:

Even though dynamic resizing works well in collectionView using the above algorithm, it's just not complete. I switched to UITableView and used auto-layouts to do dynamic resizing. It's simple, easy and works quite well.