如何在返回查看 swift 时停止 collection 触发代码

Question

我很新，如果我的标题没有正确表述，我深表歉意。我一直在努力，一直没能找到这个问题的答案。

我有水平滚动条collection。我正在尝试根据 Firestore 数组中保存的投票数据，以编程方式将 CGRect 添加到 collection 中的相关项目来直观地显示投票结果。

这是可行的，但问题是当您滚动离开（因此 collection 中的项目不在屏幕上）然后返回时，绘制 CGRects 的代码会再次触发并添加更多图形到视图。有没有办法在用户将项目滚动到屏幕外时删除这些 CGRects collection，以便当用户将项目滚动回视图时，再次触发代码它不会创建重复项？

这是显示第一次和第二次加载的几个屏幕截图

这是我的代码（单元格 b 是触发 CGrect 的地方）

//COLLECTION VIEW CODE    
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        if collectionView == self.sentCollectionView {
            let cellA = collectionView.dequeueReusableCell(withReuseIdentifier: "sCell", for: indexPath) as! SentCollectionViewCell
            
            cellA.sentQuestionLabel.text = sentMessages[indexPath.row].shoutText
            // Set up cell
            return cellA
        }
        else {
            let cellB = receivedCollectionView.dequeueReusableCell(withReuseIdentifier: "pCell", for: indexPath) as! ReceivedCollectionViewCell
            
            receivedMessages[indexPath.row].pollTotal = receivedMessages[indexPath.row].pollResults.reduce(0, +)
            print("Sum of Array is : ", receivedMessages[indexPath.row].pollTotal!)
            cellB.receivedShoutLabel.text = receivedMessages[indexPath.row].shoutText
            
            print(receivedMessages[indexPath.row].pollResults.count)
            
            if receivedMessages[indexPath.row].pollResults != [] {
                for i in 0...receivedMessages[indexPath.row].pollResults.count - 1 {
                    cellB.resultsView.addSubview(sq(pollSum: receivedMessages[indexPath.row].pollTotal!, pollResult: receivedMessages[indexPath.row].pollResults[i]))
                }
            }

            return cellB
        }
    }

//THIS DRAWS THE CGRECT
    func sq(pollSum: Int, pollResult: Int) -> UIView {
        // divide the width by total responses
        let screenDivisions = Int(view.frame.size.width) / pollSum

        // the rectangle top left point x axis position.
        let xPos = 0
        
        // the rectangle width.
        let rectWidth = pollResult * screenDivisions
        
        // the rectangle height.
        let rectHeight = 10
        
        // Create a CGRect object which is used to render a rectangle.
        let rectFrame: CGRect = CGRect(x:CGFloat(xPos), y:CGFloat(yPos), width:CGFloat(rectWidth), height:CGFloat(rectHeight))
        
        // Create a UIView object which use above CGRect object.
        let greenView = UIView(frame: rectFrame)
        
        // Set UIView background color.
        greenView.backgroundColor = UIColor.green
        
        //increment y position
        yPos = yPos + 25
        
        return greenView
        
    }

Answer 1

集合单元格已出列 dequeueReusableCell ，您需要覆盖 prepareForReuse

或设置标签

greenView.tag = 333

并在 cellForItemAt 内执行此操作

cellB.resultsView.subviews.forEach {  
   if [=11=].tag == 333 {
      [=11=].removeFromSuperview()
    }
}
if receivedMessages[indexPath.row].pollResults != [] {
    for i in 0...receivedMessages[indexPath.row].pollResults.count - 1 {
        cellB.resultsView.addSubview(sq(pollSum: receivedMessages[indexPath.row].pollTotal!, pollResult: receivedMessages[indexPath.row].pollResults[i]))
    }
}

如何在返回查看 swift 时停止 collection 触发代码

How to stop collection triggering code when scrolling back in to view swift

ios

cgrect

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