Question

我在tableview单元格周围添加了空白区域，每当我滚动时，这个阴影会越来越大，当我滚动第二次和第三次使用更大的阴影时，它会变得滞后

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! CustomCell
    cell.backgroundColor = UIColor.clear
    cell.contentView.backgroundColor = UIColor.clear

    let whiteRoundedView : UIView = UIView(frame: CGRect(x:10,y: 5,width: self.view.frame.size.width - 20,height: 117))

    whiteRoundedView.layer.backgroundColor = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1.0, 1.0, 1.0, 0.9])
    //whiteRoundedView.layer.masksToBounds = true
    whiteRoundedView.layer.cornerRadius = 5.0
    whiteRoundedView.layer.shadowOffset = CGSize(width: -1,height: 1)
    whiteRoundedView.layer.shadowOpacity = 0.2

    let shadowPath = UIBezierPath(rect: whiteRoundedView.layer.bounds)
    whiteRoundedView.layer.shouldRasterize = true
    whiteRoundedView.layer.shadowPath = shadowPath.cgPath
    cell.contentView.addSubview(whiteRoundedView)
    cell.contentView.sendSubview(toBack: whiteRoundedView)

    return cell
}

Answer 1

只需将代码放入awakefrom nib

中

  class CustomCell: UITableViewCell {



        override func awakeFromNib() {
            super.awakeFromNib()
            // Initialization code
    self.backgroundColor = UIColor.clear
        self.contentView.backgroundColor = UIColor.clear

        let whiteRoundedView : UIView = UIView(frame: CGRect(x:10,y: 5,width: self.contentView.frame.size.width - 20,height: 117))

        whiteRoundedView.layer.backgroundColor = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1.0, 1.0, 1.0, 0.9])
        //whiteRoundedView.layer.masksToBounds = true
        whiteRoundedView.layer.cornerRadius = 5.0
        whiteRoundedView.layer.shadowOffset = CGSize(width: -1,height: 1)
        whiteRoundedView.layer.shadowOpacity = 0.2

        let shadowPath = UIBezierPath(rect: whiteRoundedView.layer.bounds)
        whiteRoundedView.layer.shouldRasterize = true
        whiteRoundedView.layer.shadowPath = shadowPath.cgPath
        self.contentView.addSubview(whiteRoundedView)
        self.contentView.sendSubview(toBack: whiteRoundedView)

        }


    }

Answer 2

您不断添加阴影视图，而不必删除它们。如果您的所有单元格都需要阴影，您只需添加标记并检查具有该标记的视图是否已经存在，如下所示：

whiteRoundedView.tag = 12345

if cell.contentView.viewWithTag(12345) == nil {
    cell.contentView.addSubview(whiteRoundedView)
}

如果某些细胞有阴影但有些细胞不能这样做：

if let shadowView = cell.contentView.viewWithTag(12345) && noShadow {
    shadowView.removeFromSuperview
} else if !noShadow {
    cell.contentView.addSubview(whiteRoundedView)
}

或者像问题评论中提到的那样，您可以将其添加到自定义单元格类中：

override func awakeFromNib() {
    super.awakeFromNib()

    let whiteRoundedView : UIView = UIView(frame: CGRect(x:10,y: 5,width: self.contentView.frame.size.width - 20,height: 117))

    whiteRoundedView.layer.backgroundColor = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1.0, 1.0, 1.0, 0.9])
    whiteRoundedView.layer.cornerRadius = 5.0
    whiteRoundedView.layer.shadowOffset = CGSize(width: -1,height: 1)
    whiteRoundedView.layer.shadowOpacity = 0.2

    let shadowPath = UIBezierPath(rect: whiteRoundedView.layer.bounds)
    whiteRoundedView.layer.shouldRasterize = true
    whiteRoundedView.layer.shadowPath = shadowPath.cgPath
    self.contentView.addSubview(whiteRoundedView)
}

Answer 3

您每次都要添加whiteRoundedView。如果您使用故事板或Nib来设计Cell UI，那么您可以在那里添加whiteRoundedView或者您可以在whiteRoundedView中添加标签，并在将whiteRoundedView添加为子视图之前检查是否已经添加了该标签的任何视图。

向tableview单元格添加阴影会导致延迟滚动和复制阴影

3 个答案: