執行animateWithDuration的動畫block時默認禁用用戶交互。可以傳遞一個options為UIViewAnimationOptionAllowUserInteraction,允許視圖在動畫中響應事件
[UIView animateWithDuration:2.0 delay:0.0 options:UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction animations:^{
sv.alpha = 0.1;
} completion:nil];