在重新绘制视图时删除了绘制(rect:)中uibezier路径上的阴影设置

Question

问题：

我已经实现了一个可折叠的标题视图，其中包含弯曲的底部边框和位于滚动视图上方的渐变层。标题有一个在其 draw(rect：( 函数中绘制的投影。阴影使底部边框具有发光效果。一切看起来都不错，但是当在我的标题上调用 setNeedsDisplay(( 或重新绘制视图时，投影会消失。

问题：

如何使投影在重绘视图时保留

？法典：

override func draw(_ rect: CGRect) {
super.draw(rect)
let p1 = CGPoint(x: 0, y: self.frame.height * 0.8)
let p2 = CGPoint(x: self.frame.width / 2, y: self.frame.height * 1.06)
let p3 = CGPoint(x: self.frame.width, y: self.frame.height * 0.8)
let p4 = CGPoint(x: self.frame.width, y: 0)
let p5 = CGPoint(x: 0, y: 0)
let path = UIBezierPath()
path.move(to: p1)
path.addQuadCurve(to: p3, controlPoint: p2)
path.addLine(to: p4)
path.addLine(to: p5)
path.addLine(to: p1)
path.close()
self.shapeLayer.path = path.cgPath
self.layer.mask = self.shapeLayer
if !self.didSetGradient {
self.gradient = CustomColors.blueGreenBackgroundGradient(frame: path.bounds)
self.gradient.mask = shapeLayer
self.gradient.masksToBounds = true
self.gradient.removeFromSuperlayer()
self.layer.insertSublayer(self.gradient, at: 0)
self.didSetGradient = true
}
let context = UIGraphicsGetCurrentContext()
context?.saveGState()
context?.setShadow(offset: CGSize(width: 0, height: 2.5), blur: 15, color: CustomColors.green.cgColor)
CustomColors.blueGreen.setStroke()
UIColor.clear.setFill()
path.lineWidth = 5
path.stroke()
context?.restoreGState()        
}

Answer 1

> Aight能够弄清楚这一点。重绘视图时，贝塞尔路径阴影被隐藏，因为图层蒙版被设置为 shapeLayer。我的解决方案是使用图层的shadowPath属性绘制弯曲的阴影，并将shapeLayer作为子图层插入，而不是遮罩图层。请确保在添加渐变之前添加shapeLayer，以便渐变显示在shapeLayer的顶部。正如@dfd提到的，didSetGradient块非常俗气，但它现在正在工作！

override func draw(_ rect: CGRect) {
super.draw(rect)
let p1 = CGPoint(x: 0, y: self.frame.height * 0.8)
let p2 = CGPoint(x: self.frame.width / 2, y: self.frame.height * 1.06)
let p3 = CGPoint(x: self.frame.width, y: self.frame.height * 0.8)
let p4 = CGPoint(x: self.frame.width, y: 0)
let p5 = CGPoint(x: 0, y: 0)
let path = UIBezierPath()
path.move(to: p1)
path.addQuadCurve(to: p3, controlPoint: p2)
path.addLine(to: p4)
path.addLine(to: p5)
path.addLine(to: p1)
path.close()
self.shapeLayer.path = path.cgPath
if !self.didSetGradient {
self.layer.insertSublayer(shapeLayer, at: 0)
self.gradient = CustomColors.blueGreenBackgroundGradient(frame: path.bounds)
self.gradient.mask = shapeLayer
self.gradient.masksToBounds = true
self.layer.insertSublayer(self.gradient, at: 0)
self.didSetGradient = true
}       
self.layer.shadowPath = startPath.cgPath
self.layer.shadowColor = CustomColors.blueGreen.cgColor
self.layer.shadowOpacity = 0.5
self.layer.shadowRadius = 8
self.layer.shadowOffset = CGSize(width: 0, height: 7)
self.layer.masksToBounds = false
self.clipsToBounds = false
}