项目中有二维码，我自定制了一个界面 中间那条上下扫描线 在iOS7系统下 动不起来，但在iOS6系统下可以上下扫描动起来，贴出上下扫描动画代码 求各位大神指导

//画中间的基准线

UIView* line = [[UIView alloc] initWithFrame:CGRectMake(85, 220, 140, 1)];

line.backgroundColor = [UIColor greenColor];

[reader.view addSubview:line];

[UIView beginAnimations:@"com.mycompany.myapp.animation1"
                context:nil];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:1.0f];
[UIView setAnimationRepeatAutoreverses:YES]; // 1秒钟后开始
[UIView setAnimationRepeatCount:9999];
[UIView setAnimationDidStopSelector:@selector(animationDidStop:finished:)];
line.frame = CGRectMake(85, 340, 140, 1);
[UIView commitAnimations];
[line release];