CAShapeLayer 画直线

//　　from StackOverflow

CAShapeLayer *layer = [CAShapeLayer layer];

UIBezierPath *linePath = [UIBezierPath bezierPath];

[linePath moveToPoint: pointA];

[linePath addLineToPoint: pointB];

line.path = linePath.CGPath;

line.fillColor = nil;

line.opacity = 1.0;

line.strokeColor = [UIColor redColor].CGColor;

[layer addSublayer:line];