iOS倒计时

#import "ViewController.h"@interface ViewController ()@property (nonatomic, strong) UILabel *titleLabel;@property (nonatomic, strong) NSTimer *timer;@end@implementation ViewController- (UILabel *)titleLabel{    if (!_titleLabel) {        self.titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];        _titleLabel.center = self.view.center;        _titleLabel.backgroundColor = [UIColor orangeColor];        _titleLabel.font = [UIFont systemFontOfSize:17.0];        _titleLabel.textColor = [UIColor whiteColor];        [self.view addSubview:_titleLabel];    }    return _titleLabel;}- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.    self.timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES];    //将timer添加到运行循环，模式：NSRunLoopCommonModes监听滚动模式    [[NSRunLoop currentRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];}//获取到到期的时间，还需要转化一个取得时分秒.- (NSString *)getCurrentTime{    NSString *date = @"2015-04-16 11:54:50";    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];    [formatter setDateFormat:date];    NSString *dateTime = [formatter stringFromDate:[NSDate date]];    return dateTime;}- (void)updateTimer{    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];    NSDate *date1 = [formatter dateFromString:[self getCurrentTime]];    NSDate *date2 = [NSDate date];    NSTimeZone *zone = [NSTimeZone systemTimeZone];    NSInteger interval = [zone secondsFromGMTForDate: date2];    NSDate *localeDate = [date2  dateByAddingTimeInterval: interval];    NSTimeInterval aTimer = [localeDate timeIntervalSinceDate:date1];    //aTimer为负的 aTimer1把aTimer转为正的    NSTimeInterval aTimer1 = - aTimer;    NSInteger day = (NSInteger)(aTimer1/(3600*24));    NSInteger hour = (NSInteger)(aTimer1/3600);    NSInteger minute = (NSInteger)(aTimer1 - hour*3600)/60;    NSInteger second = (aTimer1 - hour*3600 - minute*60);    NSLog(@" %f   %ld %ld  %ld",aTimer1, hour,minute,second);    if (hour >= 24) {        hour %= 24;    }    NSLog(@" %f   %ld %ld  %ld",aTimer1, hour,minute,second);    NSString *dural = [NSString stringWithFormat:@"%ld天%ld时%ld分%ld秒", day,hour, minute,second];    if (hour <= 0 && minute <= 0 && second <= 0) {        self.titleLabel.text = @"活动已过期，谢谢关注";        [self pause];    } else {        self.titleLabel.text = dural;    }}- (void)pause{    //停止时钟，invalidate是唯一的方法，一调用就干掉timer了，想再用只能重新实例化    [self.timer invalidate];}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end