[Collection Single Selection] single selection in UICollectionView with swift #swift #UICollectionView #selection #select #single select

readme.txt

UICollectionView单选cell的解决方法
解决了：
1. 单选时改变cell状态
2. 单选状态的保存，避免cell重用时状态乱跳的问题

CollectionViewCell.swift

//custom cell class

import UIKit

class CollectionViewCell: UICollectionViewCell {
    @IBOutlet weak var nameLabel: UILabel!
    
    override var isSelected: Bool{
        didSet(newValue){
            contentView.backgroundColor = newValue ? UIColor.green : UIColor.white
        }
    }
}

ViewController.swift

import UIKit

class ViewController: UIViewController {
   //save the indexPath of last selected cell
    var lastSelectedIndexPath:IndexPath?

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

extension ViewController: UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        //if selected item is equal to current selected item, ignore it
        guard lastSelectedIndexPath != indexPath else {
            return
        }
        
        if lastSelectedIndexPath != nil {
            collectionView.deselectItem(at: lastSelectedIndexPath!, animated: false)
        }
        
        print("Selected:\(indexPath)")
        let selectedCell = collectionView.cellForItem(at: indexPath) as! CollectionViewCell
        selectedCell.isSelected = true
        lastSelectedIndexPath = indexPath
    }
}

extension ViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 20
    }
    
    func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 10
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! CollectionViewCell
        cell.nameLabel.text = "S\(indexPath.section)-R\(indexPath.row)"
        //update last select state from lastSelectedIndexPath
        cell.isSelected = (lastSelectedIndexPath == indexPath)
        return cell
        
    }
}

Not working

 override func viewDidLoad() { 
   collectionView.allowsMultipleSelection = false
 }

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
     guard lastIndex != indexPath else { return }

     if let index = lastIndex {
        let cell = collectionView.cellForItem(at: index) as? YourCell
        cell?.isSelected = false
      }
      
      let cell = collectionView.cellForItem(at: indexPath) as? YourCell
      cell?.isSelected = true
      lastIndex = indexPath
}

This works 100%!!!

`In my case, I want to change the background of the button in other words the background of the cell in the collection view:

class CustomCVCell: UICollectionViewCell {

override var isSelected: Bool {
        didSet {
            grayBackgroundViewWithImage.image =
                isSelected ? UIImage(named: "") : UIImage()
        }
    }

In the main class where the collection view is stored create this variable:

class CustomViewController: UIViewController {

///save the indexPath of last selected cell
private var lastSelectedIndexPath: IndexPath? }

In viewDidLoad() set this value to false:

customCollectionView.allowsMultipleSelection = false

Further code in data source. In my case, the first cell should be is selected:

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: CustomCVCell.cellID(),
                                                  for: indexPath) as! CustomCVCell
    
    if indexPath.row == 0 {
        lastSelectedIndexPath = indexPath
        cell.isSelected = true
    }
    
    //update last select state from lastSelectedIndexPath
    cell.isSelected = (lastSelectedIndexPath == indexPath)
    
    return cell
}

Further code in the delegate:

///UICollectionViewDelegate
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    guard lastSelectedIndexPath != indexPath else { return }

         if let index = lastSelectedIndexPath {
            let cell = collectionView.cellForItem(at: index) as! CustomCVCell
            cell.isSelected = false
          }

          let cell = collectionView.cellForItem(at: indexPath) as! CustomCVCell
          cell.isSelected = true
    lastSelectedIndexPath = indexPath
}

`

For constant index if scrolling.

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: CustomCVCell.cellID(),
for: indexPath) as! CustomCVCell

if indexPath.row == 0 && lastSelectedIndexPath == nil {
            lastSelectedIndexPath = indexPath
            cell?.isSelected = true
        } else {
            cell?.isSelected = (lastSelectedIndexPath == indexPath)
}
return cell

}