-(void)countDown:(int)count{
if(count <=0){
//倒计时已到，作需要作的事吧。
return;
}
UILabel* lblCountDown = [[UILabel alloc] initWithFrame:CGRectMake(260, 120, 50, 50)];
lblCountDown.textColor = [UIColor redColor];
lblCountDown.font = [UIFont boldSystemFontOfSize:66];
lblCountDown.backgroundColor = [UIColor clearColor];
lblCountDown.text = String(@"%d",_SettedCountDown);
[self.view addSubview:lblCountDown];
[UIView animateWithDuration:1
delay:0
options:UIViewAnimationCurveEaseOut
animations:^{
lblCountDown.alpha = 0;
lblCountDown.transform = CGAffineTransformScale(CGAffineTransformIdentity, 0.5, 0.5);
}
completion:^(BOOL finished) {
[lblCountDown removeFromSuperview];
//递归调用，直到计时为零
[self countDown:count -1];
}
];
}
原文：http://blog.csdn.net/gaoyp/article/details/20522289