當(dāng)項(xiàng)目中要用到倒計(jì)時(shí)的時(shí)候，直接把代碼拷過(guò)去

int secondsCountDown; //倒計(jì)時(shí)總時(shí)長(zhǎng)  
NSTimer *countDownTimer;  
UILabel *labelText;

然后具體實(shí)現(xiàn)

//創(chuàng)建UILabel 添加到當(dāng)前view  
labelText=[[UILabel alloc]initWithFrame:CGRectMake(10, 120, 120, 36)];  
[self.view addSubview:labelText];  

//設(shè)置倒計(jì)時(shí)總時(shí)長(zhǎng)  
secondsCountDown = 60;//60秒倒計(jì)時(shí)  
//開(kāi)始倒計(jì)時(shí)  
countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeFireMethod) userInfo:nil repeats:YES]; 

//啟動(dòng)倒計(jì)時(shí)后會(huì)每秒鐘調(diào)用一次方法 timeFireMethod  

//設(shè)置倒計(jì)時(shí)顯示的時(shí)間  
labelText.text=[NSString stringWithFormat:@"%d",secondsCountDown]; 

實(shí)現(xiàn)每秒鐘執(zhí)行的方法

-(void)timeFireMethod{  
//倒計(jì)時(shí)-1  
secondsCountDown--;  
//修改倒計(jì)時(shí)標(biāo)簽現(xiàn)實(shí)內(nèi)容  
labelText.text=[NSString stringWithFormat:@"%d",secondsCountDown];  
//當(dāng)?shù)褂?jì)時(shí)到0時(shí)，做需要的操作，比如驗(yàn)證碼過(guò)期不能提交  
if(secondsCountDown==0){  
    [countDownTimer invalidate];  
    [labelText removeFromSuperview];  
}  
}