画直线

方法一(推荐)：使用CALayer

CALayer *middleBorder = [CALayer layer];
middleBorder.frame = CGRectMake(x, y, width, height);
middleBorder.backgroundColor = UIColor.CGColor;
[myView.layer addSublayer:middleBorder];

方法二：使用UIImageView(不便于更改)

- (void)drawLineWithPoint:(CGPoint) startPoint toPoint:(CGPoint)toPoint
{
        CGSize screenSize = [[UIScreen mainScreen] applicationFrame].size;
            
        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, screenSize.width, screenSize.height)];
        //    UIImageView *imageView = [[UIImageView alloc] init];
        //    imageView.frame = self.contentView.frame;
        [self.contentView addSubview:imageView];
            
        UIGraphicsBeginImageContext(imageView.frame.size);
        [imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];
            
        //获得处理的上下文
        CGContextRef context = UIGraphicsGetCurrentContext();
            
        //指定直线样式
        CGContextSetLineCap(context, kCGLineCapSquare);
            
        //直线宽度
        CGContextSetLineWidth(context, 1.0);
            
        //设置颜色
        // red:166/255.0 green:177/255.0 blue:186/255.0
        CGContextSetRGBStrokeColor(context, 246.0/255.0, 247.0/255.0, 247.0/255.0, 1.0);
            
        //开始绘制
        CGContextBeginPath(context);
            
        //画笔移动到点(31,170)
        CGContextMoveToPoint(context, startPoint.x, startPoint.y);
            
        //下一点
        CGContextAddLineToPoint(context, toPoint.x, toPoint.y);
            
        //绘制完成
        CGContextStrokePath(context);
            
        imageView.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
            
        //    NSLog(@"%f, %f", imageView.frame.size.width, imageView.frame.size.height);
}