nstimer实现倒计时-CFANZ编程社区

// 
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerFireMethod:) userInfo:nil repeats:YES]; 
 
// 
- (void)timerFireMethod:(NSTimer *)theTimer 
{ 
BOOL timeStart = YES; 
NSCalendar *cal = [NSCalendar currentCalendar];//定义一个NSCalendar对象 
NSDateComponents *endTime = [[NSDateComponents alloc] init];    //初始化目标时间... 
NSDate *today = [NSDate date];    //得到当前时间 
 
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; 
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"]; 
NSDate *dateString = [dateFormatter dateFromString:todate]; 
NSString *overdate = [dateFormatter stringFromDate:dateString]; 
//    NSLog(@"overdate=%@",overdate); 
static int year; 
static int month; 
static int day; 
static int hour; 
static int minute; 
static int second; 
if(timeStart) {//从NSDate中取出年月日，时分秒，但是只能取一次 
year = [[overdate substringWithRange:NSMakeRange(0, 4)] intValue]; 
month = [[overdate substringWithRange:NSMakeRange(5, 2)] intValue]; 
day = [[overdate substringWithRange:NSMakeRange(8, 2)] intValue]; 
hour = [[overdate substringWithRange:NSMakeRange(11, 2)] intValue]; 
minute = [[overdate substringWithRange:NSMakeRange(14, 2)] intValue]; 
second = [[overdate substringWithRange:NSMakeRange(17, 2)] intValue]; 
timeStart= NO; 
} 
 
[endTime setYear:year]; 
[endTime setMonth:month]; 
[endTime setDay:day]; 
[endTime setHour:hour]; 
[endTime setMinute:minute]; 
[endTime setSecond:second]; 
NSDate *overTime = [cal dateFromComponents:endTime]; //把目标时间装载入date 
//用来得到具体的时差，是为了统一成北京时间 
unsigned int unitFlags = NSYearCalendarUnit| NSMonthCalendarUnit| NSDayCalendarUnit| NSHourCalendarUnit| NSMinuteCalendarUnit| NSSecondCalendarUnit; 
NSDateComponents *d = [cal components:unitFlags fromDate:today toDate:overTime options:0]; 
NSString *t = [NSString stringWithFormat:@"%d", [d day]]; 
NSString *h = [NSString stringWithFormat:@"%d", [d hour]]; 
NSString *fen = [NSString stringWithFormat:@"%d", [d minute]]; 
if([d minute] < 10) { 
fen = [NSString stringWithFormat:@"0%d",[d minute]]; 
} 
NSString *miao = [NSString stringWithFormat:@"%d", [d second]]; 
if([d second] < 10) { 
miao = [NSString stringWithFormat:@"0%d",[d second]]; 
} 
//    NSLog(@"===%@天 %@:%@:%@",t,h,fen,miao); 
[_longtime setText:[NSString stringWithFormat:@"%@天 %@:%@:%@",t,h,fen,miao]]; 
if([d second] > 0) { 
//计时尚未结束，do_something 
//        [_longtime setText:[NSString stringWithFormat:@"%@:%@:%@",d,fen,miao]]; 
} else if([d second] == 0) { 
//计时结束 do_something 
 
} else{ 
//计时器失效
[theTimer invalidate]; 
} 
 
}