UIImageView*imageView1 = [[UIImageViewalloc]initWithFrame:CGRectMake(0,100,320,20)];

[self.viewaddSubview:imageView1];

UIGraphicsBeginImageContext(imageView1.frame.size);//开始画线

[imageView1.imagedrawInRect:CGRectMake(0,0, imageView1.frame.size.width, imageView1.frame.size.height)];

CGContextSetLineCap(UIGraphicsGetCurrentContext(),kCGLineCapRound);//设置线条终点形状

CGFloatlengths[] = {10,5};

CGContextRefline =UIGraphicsGetCurrentContext();

CGContextSetStrokeColorWithColor(line, [UIColorredColor].CGColor);

CGContextSetLineDash(line,0, lengths,2);//画虚线

CGContextMoveToPoint(line,0.0,20.0);//开始画线

CGContextAddLineToPoint(line,310.0,20.0);

CGContextStrokePath(line);

imageView1.image=UIGraphicsGetImageFromCurrentImageContext();