iOS 创建计时器

@property(nonatomic,retain)NSTimer * aginDownTimer;

 self.aginDownTimer = [NSTimerscheduledTimerWithTimeInterval:1target:selfselector:@selector(timeAginMethod)userInfo:nilrepeats:YES];

-(void)timeAginMethod

{

    int i = [self.aginRefreshRateintValue];   

    i--;

    self.aginRefreshRate = [NSStringstringWithFormat:@"%d",i];

   if (i == 0)

    {

        [self.aginDownTimerinvalidate];   //停止计时器

        self.aginDownTimer = [NSTimerscheduledTimerWithTimeInterval:1target:selfselector:@selector(timeAginMethod)userInfo:nilrepeats:YES];

        self.aginRefreshRate =self.refreshRate;

        [selfupdateChatPerson];

    }

}