为什么Bezier曲线在iOS UIView中成为一种形状？

Question

I am trying to draw a Bezier curve in an iOS UIView. My code is like this:

UIBezierPath *curvePath = [UIBezierPath bezierPath];
[curvePath moveToPoint:_startPoint];
[curvePath addCurveToPoint:_endPoint controlPoint1:_controlPoint1 controlPoint2:_controlPoint2];
[[UIColor blueColor] setStroke];
curvePath.lineWidth = 8;
[curvePath stroke];
_drawingLayer = [CAShapeLayer layer];
_drawingLayer.path = curvePath.CGPath;
[self.view.layer addSublayer:_drawingLayer];

I was expecting a curved Bezier line with blue color but it turns out to be a closed black shape like this: What's wrong with my code please? Thanks.

Answer 1

You've intermixed hand-drawing with CAShapeLayer . If you're using a shape layer, you need to configure it, not try to draw the path yourself. For example:

UIBezierPath *curvePath = [UIBezierPath bezierPath];
[curvePath moveToPoint:_startPoint];
[curvePath addCurveToPoint:_endPoint controlPoint1:_controlPoint1 controlPoint2:_controlPoint2];
_drawingLayer = [CAShapeLayer layer];
_drawingLayer.path = curvePath.CGPath;

/* Configure the layer, not the current context */
_drawingLayer.strokeColor = UIColor.blueColor.CGColor;
_drawingLayer.lineWidth = 8;

[self.view.layer addSublayer:_drawingLayer];