iOS 画虚线

UIImageView *imageView1 = [[UIImageView alloc]initWithFrame:CGRectMake(, , , )];
    [self.view addSubview:imageView1];

    UIGraphicsBeginImageContext(imageView1.frame.size);   //开始画线
    [imageView1.image drawInRect:CGRectMake(, , imageView1.frame.size.width, imageView1.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);  //设置线条终点形状

    float lengths[] = {,};
    CGContextRef line = UIGraphicsGetCurrentContext();
    CGContextSetStrokeColorWithColor(line, [UIColor redColor].CGColor);

    CGContextSetLineDash(line, , lengths, );  //画虚线
    CGContextMoveToPoint(line, 0.0, 20.0);    //开始画线
    CGContextAddLineToPoint(line, 310.0, 20.0);
    CGContextStrokePath(line);

    imageView1.image = UIGraphicsGetImageFromCurrentImageContext();