我试图让这个画出一条平移手势发生的线。问题是当我尝试使用此代码时
var firstPoint: CGPoint!
var path: UIBezierPath!
@IBAction func panned(gesture: UIPanGestureRecognizer) {
switch gesture.state {
case .Began: firstPoint = gesture.locationOfTouch(0, inView: view)
case .Ended: gesture.cancelsTouchesInView = true
case .Changed:
path.moveToPoint(firstPoint)
path.addLineToPoint(gesture.translationInView(view))
path.stroke()
default: break
}
}
...我收到多个错误,我不太清楚该怎么做。
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextSaveGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextSetLineWidth: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextSetLineJoin: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextSetLineCap: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextSetMiterLimit: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextSetFlatness: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextAddPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextDrawPath: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
Apr 2 17:40:03 MacBook-Pro.local Paint[6729] <Error>: CGContextRestoreGState: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.
答案 0 :(得分:17)
这告诉您,您正在尝试在有效上下文(CGContextRef
)之外调用CoreGraphics函数。除非您在stroke
drawRect
子类或UIView
和UIGraphicsBeginImageContextWithOptions
之间(或类似内容)之间进行操作,否则不应致电UIGraphicsEndImageContext
。但是,如果您不在图形上下文中,则不能只stroke
路径。
如果您只想将此路径添加到UIView
,还可以创建CAShapeLayer
,并使用此贝塞尔路径的cgPath
,并获取结果{{1}并将其添加为视图图层的子图层。例如,在Swift 3及更高版本中:
CAShapeLayer