倒计时

@property (nonatomic, assign) NSInteger timeout;

UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];

    button.frame = CGRectMake(100, 100, 200, 100);

    [button setTitle:@"跳转" forState:UIControlStateNormal];

    [button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];

    [button setTitleColor:[UIColor grayColor] forState:UIControlStateSelected];

    [button addTarget:self action:@selector(click:) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:button];

- (void)click:(UIButton *)btn{

    [self countdownButton:btn timeout:59];

}

- (void)countdownButton:(UIButton*)button timeout:(NSInteger)totalTime

{

    //    __block int timeout = totalTime;

    _timeout = totalTime;

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_source_t _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);

    dispatch_source_set_event_handler(_timer, ^{

        if(_timeout <= 0) {

            dispatch_source_cancel(_timer);

            dispatch_async(dispatch_get_main_queue(), ^{

                button.selected = NO;

                button.userInteractionEnabled = YES;

            });

        }

        else {

            int seconds = _timeout % 60;

            button.selected = YES;

            button.userInteractionEnabled = NO;

            NSString *strTime = [NSString stringWithFormat:@"%d 秒后重新获取",seconds];

            dispatch_async(dispatch_get_main_queue(), ^{

                [button setTitle:strTime forState:UIControlStateSelected];

            });

            _timeout--;

        }

    });

    dispatch_resume(_timer);

}

倒计时

原文：http://www.cnblogs.com/h-tao/p/5156915.html