ios - Swift 3.0 以相同的开始和结束角度绘制圆导致直线
<p><p>我编写了以下代码来绘制一个包含一个整体的矩形:</p>
<pre><code>fileprivate let strokeWidth: CGFloat = 5
let shapeLayer = CAShapeLayer()
shapeLayer.strokeColor = UIColor.white.cgColor
shapeLayer.lineWidth = strokeWidth
shapeLayer.fillColor = UIColor(white: 0.5, alpha: 0.9).cgColor
let p = UIBezierPath(rect: bounds.insetBy(dx: -strokeWidth, dy: -strokeWidth))
let radius = bounds.size.width / 3
p.move(to: CGPoint(x: bounds.midX + radius, y: bounds.midY))
p.addArc(withCenter: CGPoint(x: bounds.midX, y: bounds.midY), radius: radius, startAngle: 0, endAngle: CGFloat(2 * Double.pi), clockwise: false)
p.close()
shapeLayer.path = p.cgPath
layer.addSublayer(shapeLayer)
</code></pre>
<p>这里的问题是这一行:</p>
<pre><code>p.addArc(withCenter: CGPoint(x: bounds.midX, y: bounds.midY), radius: radius, startAngle: 0, endAngle: CGFloat(2 * Double.pi), clockwise: false)
</code></pre>
<p>打印出路径的描述:
UIBezierPath: 0x6000000b35c0; MoveTo {-5, -5}, LineTo {380, -5}, LineTo {380, 672}, LineTo {-5, 672}, Close, MoveTo {312.5, 333.5}, LineTo {312.5, 333.49999999999994}, Close</p>
<p>如您所见，最后两个条目是 lineTo 和 close，这没有给我预期的结果(一个完整的圆圈)，我什么也得不到，因为 333.5 和 333.4999999 之间的线太短了。</p>
<p>在切换到 Swift 3 后出现此问题，在 Objective-C 中这不是问题。</p>
<p>将结束角度更改为 1.9 * Double.pi 也可以，不知道为什么。但是整个圆圈应该有 2 * Double.pi。</p>
<p>有什么想法还是 Swift 3 的错误？</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>试试这样:</p>
<pre><code>let bounds = UIScreen.main.bounds
let strokeWidth: CGFloat = 5
let shapeLayer = CAShapeLayer()
shapeLayer.strokeColor = UIColor.white.cgColor
shapeLayer.lineWidth = strokeWidth
shapeLayer.fillColor = UIColor(white: 0.5, alpha: 0.9).cgColor
let p = UIBezierPath(rect: bounds.insetBy(dx: -strokeWidth, dy: -strokeWidth))
let radius = bounds.size.width / 3
p.move(to: CGPoint(x: bounds.midX + radius, y: bounds.midY))
p.addArc(withCenter: CGPoint(x: bounds.midX, y: bounds.midY), radius: radius, startAngle: 2 * .pi, endAngle: 0, clockwise: false)
p.close()
shapeLayer.fillColor = UIColor.red.cgColor
shapeLayer.strokeColor = UIColor.black.cgColor
shapeLayer.lineWidth = 5
shapeLayer.path = p.cgPath
let view = UIView(frame: bounds)
view.backgroundColor = .yellow
view.layer.addSublayer(shapeLayer)
view
</code></pre>
<p> <a href="/image/9BmB9.png" rel="noreferrer noopener nofollow"><img src="/image/9BmB9.png" alt="enter image description here"/></a> </p></p>
<p style="font-size: 20px;">关于ios - Swift 3.0 以相同的开始和结束角度绘制圆导致直线，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/43361886/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/43361886/
</a>
</p>
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