draw line, draw dash line, draw star, draw rect, draw dash rect, gradientLayer
- 画线，画虚线，画五角星，画矩形，画虚线矩形，渐变色，椭圆（圆），圆角矩形
iOS 12:
more:
if you want this
layer1.mask = layer2;
layer1: gradientLayer
layer2: round rect
1.fix a little bug.
1.oval & round rect.
1.gradientLayer in iOS 12.
1.gradientLayer.
1.upload.