ios - 使用 CAShapeLayer 和 CAGradientLayer 提高渐变边框的性能

Question

我正在使用此方法将渐变边框应用于 View 。但是，当 View 位于表格 View 的单元格中时，表格 View 的滚动帧率会显着下降。有没有办法提高性能？我尝试按照 Apple 的建议将 opaque 、 drawsAsynchronously 和 shouldRasterize 设置为 true 但没有任何改变。

func addBorder(colors:[UIColor]? = nil,size:CGSize? = nil) {



    _ = self.sublayers?.filter({$0.name == "GradientBorder"}).map({$0.removeFromSuperlayer()})
    let shapeFrame = CGRect(origin: CGPointZero, size: size ?? bounds.size)
    let gradientLayer = CAGradientLayer()
    gradientLayer.name = "GradientBorder"

    gradientLayer.frame =  shapeFrame
    gradientLayer.startPoint = CGPointMake(0.0, 0.5)
    gradientLayer.endPoint = CGPointMake(1.0, 0.5)
    gradientLayer.colors = colors == nil ? [UIColor.blueColor().CGColor,UIColor.redColor().CGColor] : colors!.map({$0.CGColor})
    gradientLayer.contentsScale = UIScreen.mainScreen().scale


    let shapeLayer = CAShapeLayer()
    shapeLayer.lineWidth = 2

    shapeLayer.path = UIBezierPath(roundedRect: shapeFrame, cornerRadius: self.cornerRadius).CGPath
    shapeLayer.fillColor = nil
    shapeLayer.strokeColor = UIColor.blackColor().CGColor


    gradientLayer.shouldRasterize = true
    gradientLayer.opaque = true
    gradientLayer.drawsAsynchronously  = true
    shapeLayer.drawsAsynchronously  = true
    shapeLayer.opaque = true

    gradientLayer.mask = shapeLayer
    self.addSublayer(gradientLayer)



}

Answer 1

好的，我找到了解决方案，而且非常简单。我只是添加了这三行。

override func awakeFromNib() {
    super.awakeFromNib()
    // Initialization code
    self.layer.shouldRasterize = true
    self.opaque = true
    self.layer.rasterizationScale = UIScreen.mainScreen().scale
}