Question

我正在向UICollectionView动态添加数据。每当我有一个新数据时，它会清除所有现有数据并加载一个新数据集。这是代码，

self.conversation.removeAll()
self.collectionView.reloadData()

self.conversation.insert(messageWrapper(description: "Some text", origin: "user"), at: 0)
self.collectionView.reloadData()

ItemAtIndexPath

中的代码

func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
        let textViewCell = cell as! TextCollectionViewCell
        let description = conversation[indexPath.row].description
        let origin = conversation[indexPath.row].origin

        textViewCell.textView.text = description
        textViewCell.textView.textAlignment = origin == "arvis" ? NSTextAlignment.left : NSTextAlignment.right
    }

问题它删除了所有现有数据，在加载新数据时，它与之前的数据重叠，即，如果我有Hello并添加I am good，它会显示Hello和'我很好'。

为什么会这样？

更新1：
cellForItemAt

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let textViewCell = collectionView.dequeueReusableCell(withReuseIdentifier: "textViewCell", for: indexPath) as! TextCollectionViewCell
        let description = conversation[indexPath.row].description
        let origin = conversation[indexPath.row].origin

        textViewCell.awakeFromNib()
        textViewCell.textView.text = description
        textViewCell.textView.textAlignment = origin == "arvis" ? NSTextAlignment.left : NSTextAlignment.right

        return textViewCell
    }

TextCollectionViewCell
单元格的标识符类

class TextCollectionViewCell: UICollectionViewCell {

    var textView: UITextView!

    override func awakeFromNib() {
        textView = UITextView(frame: contentView.frame)
        textView.textColor = UIColor.white
        textView.font = UIFont.systemFont(ofSize: 18)
        textView.layer.backgroundColor = UIColor.clear.cgColor
        textView.contentMode = .scaleAspectFill
        textView.clipsToBounds = true
        contentView.addSubview(textView)
    }
}

Answer 1

现有数据被清除，因为您正在清除collectionView的数据源并重新加载它。

尝试将新值附加到conversation数组，然后重新加载collectionView。

如果问题与过度使用相关，请尝试从textViewCell.textView更新cellForItemAtIndexPath，而不是更新textViewCell.textView中的willDisplaycell

Answer 2

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

    let textViewCell = cell as! TextCollectionViewCell

    let description = conversation[indexPath.row].description
        let origin = conversation[indexPath.row].origin

        textViewCell.textView.text = description
        textViewCell.textView.textAlignment = origin == "arvis" ? NSTextAlignment.left : NSTextAlignment.right

    return textViewCell
}

尝试此操作，而不是在willDisplay cell:使用cellForItemAt indexPath:

中进行更新

Swift - UICollectionView removeAll（）暂时清除单元格

2 个答案: