执行animateWithDuration的动画block时默认禁用用户交互。可以传递一个options为UIViewAnimationOptionAllowUserInteraction，允许视图在动画中响应事件
[UIView animateWithDuration:2.0 delay:0.0 options:UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction animations:^{
sv.alpha = 0.1;
} completion:nil];
