UICollectionView.reloadData() 更改单元格顺序 | iOS Swift

Question

所以我正在使用一个简单的 UICollectionView，X 行 3 列，其中 X 由变量 matchesFromSelectedSession.count + 1 设置。以下是我用于 collectionView 的委托函数：

func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 3
}

func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    let cellHeight = 15.0 as CGFloat
    return CGSizeMake(collectionView.bounds.size.width/3, cellHeight)
}

func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
    return matchesFromSelectedSession.count + 1
}

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let reuseIdentifier = "MatchCollectionViewCell"
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! MatchCollectionViewCell
    cell.matchCollectionLabel = UILabel(frame: CGRectMake(0,0,collectionView.bounds.width/3 - 3.0,15))
    cell.matchCollectionLabel.textColor = UIColor.blackColor()
    cell.systemLayoutSizeFittingSize(cell.frame.size, withHorizontalFittingPriority: UILayoutPriorityDefaultHigh, verticalFittingPriority: UILayoutPriorityDefaultLow)
    cell.matchCollectionLabel.font = UIFont(name: "Helvetica Neue", size:12)
    if indexPath.section == 0 {
        switch indexPath.row {
        case 0:
            cell.matchCollectionLabel.text = "Match #"
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            cell.matchCollectionLabel.textAlignment = NSTextAlignment.Right
            break
        case 1:
            cell.matchCollectionLabel.text = "Record"
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            cell.matchCollectionLabel.textAlignment = NSTextAlignment.Center
            break
        case 2:
            cell.matchCollectionLabel.text = "Outcome"
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            break
        default:
            cell.matchCollectionLabel.text = ""
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            break
        }
    } else {
        switch indexPath.row {
        case 0:
            cell.matchCollectionLabel.text = "\(indexPath.section)"
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            cell.matchCollectionLabel.textAlignment = NSTextAlignment.Right
            break
        case 1:
            cell.matchCollectionLabel.text = matchesFromSelectedSession[indexPath.section - 1].matchRecord()
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            cell.matchCollectionLabel.textAlignment = NSTextAlignment.Center
            break
        case 2:
            let outcome = matchesFromSelectedSession[indexPath.section - 1].matchOutcome()
            switch outcome {
            case "W":
                cell.matchCollectionLabel.text = "Win"
                cell.matchCollectionLabel.textColor = UIColor.greenColor()
                break
            case "D":
                cell.matchCollectionLabel.text = "Draw"
                cell.matchCollectionLabel.textColor = UIColor.blueColor()
                break
            case "L":
                cell.matchCollectionLabel.text = "Loss"
                cell.matchCollectionLabel.textColor = UIColor.redColor()
                break
            default:
                cell.matchCollectionLabel.textColor = UIColor.blackColor()
                break
            }
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            break
        default:
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            cell.matchCollectionLabel.text = ""
            break
        }
    }
    //add subview if new cell otherwise tag cell to know to reuse next time
    if cell.tag != 19 {
        cell.addSubview(cell.matchCollectionLabel)
    }
    cell.tag = 19
    return cell
}

我使用的自定义单元格 MatchCollectionViewCell 仅包含一个标签 matchCollectionLabel，仅此而已。我在视图的 viewDidAppear 函数中使用 self.matchCollectionView.reloadData() 来处理辅助视图更改 table 并返回原始视图的情况。

我在第一次使用后标记单元格，我不会在每次 viewDidAppear 后不断向单元格添加不必要的子视图。

table 在初始设置后看起来不错，但在调用 reloadData 后，collectionView 的单元格顺序发生变化和混乱。如果我编辑单元格的数量，reloadData() 会更新以正确显示单元格数量的变化，但单元格的顺序仍然不正确。

这里是reloadData前后的图片

http://imgur.com/wqfXqLG.png

如有任何帮助，我们将不胜感激！谢谢！

Answer 1

您每次都在创建一个新标签。如果标签不是 19，则只能将它添加为子视图，但你总是分配一个新标签。

这意味着当您重复使用一个单元格时，您正在更新一个新标签，而不是已添加到该单元格的标签，因此您的更改不可见。

您可以将标签检查移动到函数的顶部并使用它来控制标签的分配，或者将 matchCollectionLabel 定义为可选，然后您可以检查它 nil:

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let reuseIdentifier = "MatchCollectionViewCell"
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! MatchCollectionViewCell

    if cell.matchCollectionLabel == nil {
        cell.matchCollectionLabel = UILabel(frame: CGRectMake(0,0,collectionView.bounds.width/3 - 3.0,15))
        cell.matchCollectionLabel!.textColor = UIColor.blackColor()
        cell.systemLayoutSizeFittingSize(cell.frame.size, withHorizontalFittingPriority: UILayoutPriorityDefaultHigh, verticalFittingPriority: UILayoutPriorityDefaultLow)
        cell.matchCollectionLabel!.font = UIFont(name: "Helvetica Neue", size:12)
        cell.addSubview(cell.matchCollectionLabel!)
    }

    if indexPath.section == 0 {
        switch indexPath.row {
        case 0:
            cell.matchCollectionLabel!.text = "Match #"
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            cell.matchCollectionLabel!.textAlignment = NSTextAlignment.Right
            break
        case 1:
            cell.matchCollectionLabel!.text = "Record"
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            cell.matchCollectionLabel!.textAlignment = NSTextAlignment.Center
            break
        case 2:
            cell.matchCollectionLabel!.text = "Outcome"
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            break
        default:
            cell.matchCollectionLabel!.text = ""
            cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            break
        }
    } else {
        switch indexPath.row {
        case 0:
            cell.matchCollectionLabel!.text = "\(indexPath.section)"
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            cell.matchCollectionLabel!.textAlignment = NSTextAlignment.Right
            break
        case 1:
            cell.matchCollectionLabel!.text = matchesFromSelectedSession[indexPath.section - 1].matchRecord()
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            cell.matchCollectionLabel!.textAlignment = NSTextAlignment.Center
            break
        case 2:
            let outcome = matchesFromSelectedSession[indexPath.section - 1].matchOutcome()
            switch outcome {
            case "W":
                cell.matchCollectionLabel!.text = "Win"
                cell.matchCollectionLabel!.textColor = UIColor.greenColor()
                break
            case "D":
                cell.matchCollectionLabel!.text = "Draw"
                cell.matchCollectionLabel!.textColor = UIColor.blueColor()
                break
            case "L":
                cell.matchCollectionLabel!.text = "Loss"
                cell.matchCollectionLabel!.textColor = UIColor.redColor()
                break
            default:
                cell.matchCollectionLabel!.textColor = UIColor.blackColor()
                break
            }
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            break
        default:
            if indexPath.section%2 == 0 {
                cell.backgroundColor = ImageEditor.colorWithHexString("EFEFF4")
            }
            cell.matchCollectionLabel!.text = ""
            break
        }
    }
    return cell
}

UICollectionView.reloadData() 更改单元格顺序 | iOS Swift

UICollectionView.reloadData() changes cell order | iOS Swift

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