在指定view上绘制虚线

/**
 绘制虚线

 @param lineView    需要绘制成虚线的view
 @param lineLength  虚线的宽度
 @param lineSpacing 虚线的间距
 @param lineColor   虚线的颜色
 */
- (void)drawDashLine:(UIView *)lineView lineLength:(int)lineLength lineSpacing:(int)lineSpacing lineColor:(UIColor *)lineColor
{
    //  根据lineView的宽高，决定虚线是水平方向还是竖直方向
    BOOL isHorizontally = lineView.bounds.size.width > lineView.bounds.size.height;
    
    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    [shapeLayer setBounds:lineView.bounds];
    if (isHorizontally) {
        [shapeLayer setPosition:CGPointMake(CGRectGetWidth(lineView.frame) / 2,
                                            CGRectGetHeight(lineView.frame))];
    }else {
        [shapeLayer setPosition:CGPointMake(CGRectGetWidth(lineView.frame),
                                            CGRectGetHeight(lineView.frame) / 2)];
    }
    [shapeLayer setFillColor:[UIColor clearColor].CGColor];
    //  设置虚线颜色为blackColor
    [shapeLayer setStrokeColor:lineColor.CGColor];
    //  设置虚线宽度
    if (isHorizontally) {
        [shapeLayer setLineWidth:CGRectGetHeight(lineView.frame)];
    }else {
        [shapeLayer setLineWidth:CGRectGetWidth(lineView.frame)];
    }
    [shapeLayer setLineJoin:kCALineJoinRound];
    //  设置线宽，线间距
    [shapeLayer setLineDashPattern:[NSArray arrayWithObjects:[NSNumber numberWithInt:lineLength], [NSNumber numberWithInt:lineSpacing], nil]];
    //  设置路径
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, 0, 0);
    if (isHorizontally) {
        CGPathAddLineToPoint(path, NULL, CGRectGetWidth(lineView.frame), 0);
    }else {
        CGPathAddLineToPoint(path, NULL, 0, CGRectGetHeight(lineView.frame));
    }
    [shapeLayer setPath:path];
    CGPathRelease(path);
    //  把绘制好的虚线添加上来
    [lineView.layer addSublayer:shapeLayer];
}