我有一个 UIView 的子类，其中包含一堆使用 CGPAth 绘制的图形。我需要知道触摸何时触及这些路径之一，以及是哪一条。
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for t in touches {
for p in myDrawnPaths {
if(p.contains(t.location(in: self)) {
doStuffWith(p)
}
}
}
}
有时，此代码会导致 doStuffWith() 在多个路径上执行，包括那些远离命中位置的路径。我做了一些检查，发现不应该受到影响的路径有些奇怪:
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for t in touches {
for p in myDrawnPaths {
print(p.contains(t.location(in: self))) //true
print(p.boundingBox.contains(t.location(in: self))) //false!
}
}
}
嗯？边界框不应该包含整个路径，这意味着路径内的点一定在边界框内吗？
问题仅在此类测试中出现——当我使用 CoreGraphics API 以相同的 CGPath 绘制和动画时，所有显示都是正确的。
更新
我试图在 Playgrounds 中通过简单的实验路径重现该问题，但无法重现，因此我不得不从我的实际应用中获取它。
(75.0, 264.0) is in
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正如我们所见，路径中所有点的 X 坐标都在 200 秒内，但 X 坐标为 75 的点被计算为在该路径内。
如果我将 close 命令附加到路径，问题就会消失，但这会带来其他问题:
CGPath 的
contains如何在开放路径上工作，如果有的话，记录在哪里？为什么这会影响
contains方法的结果，而不是我在屏幕上看到的任何内容？例如，如果我告诉相应的CALayer填充某种颜色，该颜色不会超出应有的位置。
最佳答案
在 Playground 上进行试验后，我发现 CGRect.contains(:) 方法对于 x 值大于或等于的点返回 false > maxX 值或大于或等于 maxY 值的 y 值。
事实证明，CGRect 的 documentation 说了类似的话:
如果一个点的坐标位于矩形内部或最小 X 或最小 Y 边上，则该点被视为在矩形内部。
我认为文档措辞不佳，因为最大 X 和最小 Y 边的交点未包含在最小 X 和最大 Y 边的交点中。
下面是演示这个的代码:
let rect = CGRect(x: 0, y: 0, width: 200, height: 200)
rect.contains(CGPoint(x: 0, y: 0)) // true
rect.contains(CGPoint(x: rect.midX, y: 0)) // true
rect.contains(CGPoint(x: 0, y: rect.midY)) // true
rect.contains(CGPoint(x: 200, y: 200)) // false
rect.contains(CGPoint(x: 200, y: 0)) // false
rect.contains(CGPoint(x: 0, y: 200)) // false
rect.contains(CGPoint(x: 0, y: rect.maxY)) // false
rect.contains(CGPoint(x: rect.maxX, y: 0)) // false
rect.contains(CGPoint(x: rect.maxX, y: rect.maxY)) // false
rect.maxX // 200
rect.maxY // 200
此外，documentation 声明 boundingBox 包含路径的所有点，包括贝塞尔曲线和二次曲线的控制点。您可能想改用 boundingBoxOfPath。
关于ios - 为什么 CGPath 包含测试有时会在路径外的点上返回 true？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/52797372/