Swift 3，用特殊的lineCap画圆

Question

Currently I'm using CAShapeLayer and UIBezierPath to draw a line for avatar. It's Ok for the normal one with lineCap = kCALineCapRound . BUT I've been STRUGGLING to draw line with START and END lineCap like image below:

Answer 1

You can't draw this circle with a shape layer, because a shape layer supports only one single stroke color. You should write your own layer class where you should draw three separate circle segments with kCALineCapRound :

1. A full yellow circle.
2. Draw the blue segment over the yellow circle. It is visible and you can see the rounded ends.
3. Draw a segment of the yellow circle, say 5 degrees of the top. Then you can also see the rounded end of the yellow line.

You should use CGPath and CGContext instead of UIBezierPath .