Swift CollectionView 取消选择不起作用

Posted 2023-03-11

【中文标题】Swift CollectionView 取消选择不起作用

【英文标题】：Swift CollectionView Deselection not working

【发布时间】：2017-11-20 07:30:15

【问题描述】：

我正在使用自定义 UICollectionViewFlowLayout 类来实现滚动视图的多滚动行为。没有问题。 但是要进行自定义选择和取消选择，我需要在 shouldSelectItemAt 函数中使用自定义代码来正确选择/取消选择。 这是它的代码：

MyCustomCollectionViewController 内部：

func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool 
if(collectionView == customContentCollectionView)

let cell:MyContentCell = collectionView.cellForItem(at: indexPath)! as! MyCollectionViewController.MyContentCell
if(self.bubbleArray[indexPath.section][indexPath.item].umid != "")

// DESELECTION LOGIC
if(previouslySelectedIndex != nil)

let (bubbleBorder, bubbleFill) = getBubbleColor(selected: false)

// following line is error prone (executes but may or may not fetch the cell, sometimes deselect sometimes doesn't)
let prevCell = try collectionView.cellForItem(at: previouslySelectedIndex) as? MyCollectionViewController.MyContentCell

prevCell?.shapeLayer.strokeColor = bubbleBorder.cgColor
prevCell?.shapeLayer.fillColor = bubbleFill.cgColor
prevCell?.shapeLayer.shadowOpacity = 0.0
prevCell?.labelCount.textColor = bubbleBorder

previouslySelectedIndex = []
previouslySelectedIndex = indexPath


// SELECTION LOGIC
if(self.bubbleArray[indexPath.section][indexPath.item].interactions != "")
let (bubbleBorder, bubbleFill) = getBubbleColor(selected: true)
cell.shapeLayer.strokeColor = bubbleBorder.cgColor
cell.shapeLayer.fillColor = bubbleFill.cgColor
cell.shapeLayer.shadowOffset = CGSize(width: 0, height: 2)
cell.shapeLayer.shadowOpacity = 8
cell.shapeLayer.shadowRadius = 2.0
cell.labelCount.textColor = UIColor.white


return false

return true

MyContentCell 的代码：

class MyContentCell: UICollectionViewCell // CODE TO CREATE CUSTOM CELLS

var gradient = CAGradientLayer()
var shapeLayer = CAShapeLayer()
var horizontalLine = UIView()
var verticalLeftLine = UIView()

required init(coder aDecoder: NSCoder) 
super.init(coder: aDecoder)!
setup()


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


let labelCount: UILabel = 
let myLabel = UILabel()
return myLabel
()


func setup() // initializing cell components here as well as later in cellForItemAt method
............


override func prepareForReuse() 
self.shapeLayer.fillColor = UIColor.white.cgColor
self.shapeLayer.shadowOpacity = 0.0

问题可能是，当一个单元格被选中并且刚刚拖出屏幕时，它可能不会被破坏，这就是为什么准备重用功能没有跟踪它以进行取消选择。那么请告诉我如何取消选择刚刚离开屏幕的单元格（可见索引）？

【问题讨论】：

CollectionView?.collectionViewLayout.invalidateLayout()

【参考方案1】：

你需要使布局无效

collectionView?.collectionViewLayout.invalidateLayout() 

【讨论】：

它在里面没有工作应该选择方法。我应该把这段代码放在哪里？