单元格在滚动时应用额外的阴影

Question

我正在尝试添加阴影并添加到自定义UITableViewCell，一切正常但是当我滚动tableview时，单元格的阴影将被应用于其上并使阴影更厚。这是我的代码：

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! DriverCell


        //Create space between cells
        cell.contentView.backgroundColor = UIColor(red:0.88, green:0.94, blue:0.99, alpha:1.00)
        let whiteRoundedView : UIView = UIView(frame: CGRect(x:8, y:10, width: self.view.frame.size.width - 15 , height:150))
        whiteRoundedView.layer.backgroundColor = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1.0, 1.0, 1.0, 1.0])
        whiteRoundedView.layer.masksToBounds = false
        whiteRoundedView.layer.cornerRadius = 9.0
        whiteRoundedView.layer.shadowOffset = CGSize(width: 0, height: 0)
        whiteRoundedView.layer.shadowRadius = 1.5
        whiteRoundedView.layer.shadowOpacity = 0.2
        whiteRoundedView.clipsToBounds = false
        cell.contentView.addSubview(whiteRoundedView)
        cell.contentView.sendSubview(toBack: whiteRoundedView)


        return cell
    }

1. 默认阴影
2. 应用了额外的阴影

Answer 1

UITableViewCell是一个可重用的视图。这意味着因为滚动时会调用cellForRow，所以会在某个点再次应用阴影。

例如：视图A，B，C在屏幕上，当您向下滚动并且视图A被隐藏时，视图A将被重用，并且将再次为视图A创建阴影。

对于你的情况，我建议你在DriverCell中添加阴影，如下所示：

class DriverCell: UITableViewCell {

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

    contentView.backgroundColor = UIColor(red:0.88, green:0.94, blue:0.99, alpha:1.00)
    let whiteRoundedView : UIView = UIView(frame: CGRect(x:8, y:10, width: frame.size.width - 15 , height:150))
    whiteRoundedView.layer.backgroundColor = CGColor(colorSpace: CGColorSpaceCreateDeviceRGB(), components: [1.0, 1.0, 1.0, 1.0])
    whiteRoundedView.layer.masksToBounds = false
    whiteRoundedView.layer.cornerRadius = 9.0
    whiteRoundedView.layer.shadowOffset = CGSize(width: 0, height: 0)
    whiteRoundedView.layer.shadowRadius = 1.5
    whiteRoundedView.layer.shadowOpacity = 0.2
    whiteRoundedView.clipsToBounds = false
    contentView.addSubview(whiteRoundedView)
    contentView.sendSubview(toBack: whiteRoundedView)
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

}

这样，在视图初始化时将绘制阴影，在

之后不再绘制阴影