相关疑难解决方法(0)

我正在创建一个CAShapeLayer用作UIView图层的掩码.我用a UIBezierPath来绘制形状图层.它工作得很好,除了我画画时得到一些奇怪的结果.几何体的行为不符合预期.我正试图在右上角绘制简单的"馅饼切片":

#define degreesToRadians(x) ((x) * M_PI / 180.0)

...

// "layer" refer's to the UIView's root layer

CAShapeLayer *maskLayer = [CAShapeLayer layer];

maskLayer.frame =
    layer.presentationLayer ? 
    ((CAGradientLayer *)layer.presentationLayer).bounds : layer.bounds;
maskLayer.fillRule = kCAFillRuleEvenOdd;
maskLayer.needsDisplayOnBoundsChange = YES;

CGFloat maskLayerWidth = maskLayer.bounds.size.width;
CGFloat maskLayerHeight = maskLayer.bounds.size.height;
CGPoint maskLayerCenter = 
    CGPointMake(maskLayerWidth/2,maskLayerHeight/2);

UIBezierPath *path = [UIBezierPath bezierPath];

[path moveToPoint:maskLayerCenter];

[path addArcWithCenter:maskLayerCenter radius:(maskLayerWidth/2)
startAngle:degreesToRadians(0) endAngle:degreesToRadians(90) clockwise:YES];

[path closePath];


maskLayer.path = path.CGPath;

layer.mask = maskLayer;

最终结果是在右下角绘制了饼图切片.弧的第一个点是以90度绘制的,然后是180度.即使我使用0度和90度角,它为什么会这样做？