使用UIBezierPath获取“无效上下文”错误
问题描述:
我正试图让这个画线在平底锅手势发生的地方。问题是当我尝试使用此代码使用UIBezierPath获取“无效上下文”错误
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
}
}
...我得到多个错误,我不太确定该怎么办。
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
这是告诉你,你正在尝试调用一个有效的上下文(一CGContextRef
)之外CoreGraphics中的功能。您不应该拨打电话号码stroke
,除非您在的子类别中或在UIGraphicsBeginImageContextWithOptions
和UIGraphicsEndImageContext
(或其他类似的东西)之间进行。但是,如果您不在图形上下文中,则不能只是stroke
路径。
如果你只是想这个路径添加到UIView
,你还可以创建一个CAShapeLayer
,并使用该贝塞尔曲线的cgPath
,并承担由此产生的CAShapeLayer
并将其添加为视图的层的一个子层。例如,在Swift 3和更高版本中:
var drawPath: UIBezierPath!
var shapeLayer: CAShapeLayer!
func handlePan(gesture: UIPanGestureRecognizer) {
let location = gesture.location(in: gesture.view)
if gesture.state == .began {
drawPath = UIBezierPath()
drawPath.move(to: location)
shapeLayer = CAShapeLayer()
shapeLayer.strokeColor = UIColor.black.cgColor
shapeLayer.fillColor = UIColor.clear.cgColor
shapeLayer.lineWidth = 4.0
gesture.view?.layer.addSublayer(shapeLayer)
} else if gesture.state == .changed {
drawPath.addLine(to: location)
shapeLayer.path = drawPath.cgPath
}
}
谢谢,它的工作原理 – traw1233 2015-04-03 01:44:48