#import<uikit uikit.h="">@interfaceViewController : UIViewController@property(weak, nonatomic) IBOutlet UILabel *dayLabel;@property(weak, nonatomic) IBOutlet UILabel *hourLabel;@property(weak, nonatomic) IBOutlet UILabel *minuteLabel;@property(weak, nonatomic) IBOutlet UILabel *secondLabel;@end</uikit>

#import"ViewController.h"@interfaceViewController (){  dispatch_source_t _timer;}@end@implementationViewController/** *  獲取當天的年月日的字符串 *  這里測試用 *  @return 格式為年-月-日 */-(NSString *)getyyyymmdd{ NSDate *now = [NSDate date]; NSDateFormatter *formatDay = [[NSDateFormatter alloc] init]; formatDay.dateFormat = @"yyyy-MM-dd"; NSString *dayStr = [formatDay stringFromDate:now]; returndayStr;}- (void)viewDidLoad { [superviewDidLoad]; NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init]; [dateFormatter setDateFormat:@"yyyy-MM-dd"]; NSDate *endDate = [dateFormatter dateFromString:[self getyyyymmdd]]; NSDate *endDate_tomorrow = [[NSDate alloc] initWithTimeIntervalSinceReferenceDate:([endDate timeIntervalSinceReferenceDate] +24*3600)]; NSDate *startDate = [NSDate date]; NSTimeInterval timeInterval =[endDate_tomorrow timeIntervalSinceDate:startDate]; if(_timer==nil) {  __blockinttimeout = timeInterval; //倒計時時間  if(timeout!=0) {   dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);   _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0,0,queue);   dispatch_source_set_timer(_timer,dispatch_walltime(NULL,0),1.0*NSEC_PER_SEC,0);//每秒執行   dispatch_source_set_event_handler(_timer, ^{    if(timeout<=0){//倒計時結束，關閉     dispatch_source_cancel(_timer);     _timer = nil;     dispatch_async(dispatch_get_main_queue(), ^{      self.dayLabel.text = @"";      self.hourLabel.text = @"00";      self.minuteLabel.text = @"00";      self.secondLabel.text = @"00";     });    }else{     intdays = (int)(timeout/(3600*24));     if(days==0) {      self.dayLabel.text = @"";     }     inthours = (int)((timeout-days*24*3600)/3600);     intminute = (int)(timeout-days*24*3600-hours*3600)/60;     intsecond = timeout-days*24*3600-hours*3600-minute*60;     dispatch_async(dispatch_get_main_queue(), ^{      if(days==0) {       self.dayLabel.text = @"0天";      }else{       self.dayLabel.text = [NSString stringWithFormat:@"%d天",days];      }      if(hours<10) {       self.hourLabel.text = [NSString stringWithFormat:@"0%d",hours];      }else{       self.hourLabel.text = [NSString stringWithFormat:@"%d",hours];      }      if(minute<10) {       self.minuteLabel.text = [NSString stringWithFormat:@"0%d",minute];      }else{       self.minuteLabel.text = [NSString stringWithFormat:@"%d",minute];      }      if(second<10) {       self.secondLabel.text = [NSString stringWithFormat:@"0%d",second];      }else{       self.secondLabel.text = [NSString stringWithFormat:@"%d",second];      }     });     timeout--;    }   });   dispatch_resume(_timer);  } }}<span style="font-family: Arial, Verdana, sans-serif;">效果：</span>