ios - 圆角改变 UIView 大小

Question

在自定义 tableView 单元格中，我想创建顶部带有圆角的 UIView。这是我设置 UIView 约束的代码部分

headerView.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 8).isActive = true
headerView.topAnchor.constraint(equalTo: self.topAnchor, constant: 4).isActive = true
headerView.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -8).isActive = true
headerView.heightAnchor.constraint(equalToConstant: 40).isActive = true

这部分的波纹管设置圆角 View 我做了以下事情:

self.layoutIfNeeded()
let rectShape = CAShapeLayer()
rectShape.bounds = headerView.layer.frame
rectShape.position = headerView.center
rectShape.path = UIBezierPath(roundedRect: headerView.layer.bounds, byRoundingCorners: [ .topLeft, .topRight], cornerRadii: CGSize(width: 10, height: 10)).cgPath
headerView.layer.backgroundColor = UIColor.green.cgColor
headerView.layer.mask = rectShape

问题是，当此代码块用于设置圆角时， View 的大小会发生变化。这是输出

没有这部分代码的结果如下:

我的问题是为什么 View 大小会发生变化？我做错了什么？

Answer 1

这是因为一旦标题 View 的约束被调整大小时，您的 CAShapeLayer 不会自动调整大小。每当调整 View 大小时，您都需要更新路径:

  let headerView: UIView!

  override func awakeFromNib() {
    super.awakeFromNib()

    headerView = UIView(frame: bounds)
    headerView.frame = bounds

    headerView.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 8).isActive = true
    headerView.topAnchor.constraint(equalTo: self.topAnchor, constant: 4).isActive = true
    headerView.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -8).isActive = true
    headerView.heightAnchor.constraint(equalToConstant: 40).isActive = true


    let rectShape = CAShapeLayer()
    rectShape.bounds = headerView.layer.frame
    rectShape.position = headerView.center

    headerView.layer.backgroundColor = UIColor.green.cgColor
    headerView.layer.mask = rectShape
  }

  override func layoutSubviews() {
    super.layoutSubviews()

    rectShape.path = UIBezierPath(roundedRect: headerView.layer.bounds, byRoundingCorners: [ .topLeft, .topRight], cornerRadii: CGSize(width: 10, height: 10)).cgPath
  }

我以 awakeFromNib 为例。您的 View 设置在您的自定义 UITableViewCell 类中可能有所不同。