无法在 Swift 中更改 CollectionView 单元格背景颜色

Question

我已经给出了这样的图像和标签的约束

。

代码：使用此代码我可以获得

selectedNamesArray

，但无法更改单元格颜色。我哪里错了？故事板约束是否有问题，导致单元 BG 没有改变？或任何其他编码错误？谁能解释一下细胞背景变化的问题和解决方案

class TestCollectionCell: UICollectionViewCell{
@IBOutlet weak var roundImg: UIImageView!
@IBOutlet weak var titleLbl: UILabel!

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

override func layoutSubviews() {
    super.layoutSubviews()
    roundImg.layer.cornerRadius = roundImg.frame.width / 2
    roundImg.contentMode = .scaleToFill
    roundImg.clipsToBounds = true
}
}


override func viewDidLoad() {
super.viewDidLoad()

collectionView.delegate = self
collectionView.dataSource = self

let layOut = UICollectionViewFlowLayout()
layOut.scrollDirection = .vertical

collectionView.collectionViewLayout = layOut
collectionView.allowsMultipleSelection = true
GenericCodableServicecall()
}

var cvWidth: CGFloat = -1.0

override func viewDidLayoutSubviews() {
super.viewDidLayoutSubviews()
if cvWidth != collectionView.frame.size.width {
    cvWidth = collectionView.frame.size.width
    if let fl = collectionView.collectionViewLayout as? UICollectionViewFlowLayout {

        let nColumns: Int = 4
        
        let sideSpace: CGFloat = fl.sectionInset.left + fl.sectionInset.right
        
        let totalEmptyspace: CGFloat = sideSpace + (CGFloat(nColumns) * 3.0)
        
        let w = (cvWidth - totalEmptyspace) / CGFloat(nColumns)
        fl.itemSize = .init(width: w, height: w)

        fl.minimumInteritemSpacing = 0.0
    }
}
}

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
namesArray.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "TestCollectionCell", for: indexPath) as! TestCollectionCell
cell.layoutIfNeeded()
cell.titleLbl.text = namesArray[indexPath.row]
return cell
}

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

print("in select..")

let cell = collectionView.cellForItem(at: indexPath) as! TestCollectionCell
let selectedName = namesArray[indexPath.row]
if let inx = selectedNamesArray.firstIndex(of: selectedName){
    selectedNamesArray.remove(at: inx)
    cell.backgroundColor = UIColor.red
}
else{
    selectedNamesArray.append(selectedName)
    cell.backgroundColor = UIColor.yellow
}
print(selectedNamesArray)
}

当我选择/取消选择时无法更改单元格背景，始终仅显示绿色背景。

Answer 1

尝试

let cell = collectionView.cellForItem(at: indexPath) as! TestCollectionCell
cell.contentView.backgroundColor = UIColor.white (What ever color u want change)

Answer 2

为

selected

状态添加一个额外的数组是非常糟糕的做法。如果您使用一个，则必须在

cellForItemAt

中设置颜色，因为当用户滚动时会重复使用单元格。

更好的方法是使用带有成员的数据源结构

isSelected

struct Person {
    let name: String
    var isSelected = false
}

那么数据源数组就是

var people = [Person]()

数据来源和方法是

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    people.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "TestCollectionCell", for: indexPath) as! TestCollectionCell
    cell.layoutIfNeeded()
    let person = people[indexPath.row]
    cell.titleLbl.text = person.name
    cell.backgroundColor = person.isSelected ? .red : .yellow
    return cell
}

在

didSelect

中，只需在给定的

isSelected

处切换项目的

indexPath

并重新加载项目

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

    print("in select..")

    people[indexPath.row].isSelected.toggle()
    collectionView.reloadItems(at: [indexPath])
}