设置圆角
CGRect rect = self.bounds;
// Create the path
UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:rect
byRoundingCorners:corners
cornerRadii:CGSizeMake(radius, radius)];
// Create the shape layer and set its path
CAShapeLayer *maskLayer = [CAShapeLayer layer];
maskLayer.frame = rect;
maskLayer.path = maskPath.CGPath;
// Set the newly created shape layer as the mask for the view's layer
self.layer.mask = maskLayer;