title: NStimer in not working properly in iOS
body: <p>I am displaying time using the following code... I have scroll view in my viewController... Here i am displaying time starting with 00:00.00 (mm:ss:SS) (minutes:seconds:milliseconds) and aim incrementing the milliseconds , seconds based on milliseconds, minutes based on seconds... But i want to display time starting from 75:00.00 (mm:ss:SS) and i want to decrement the milliseconds, seconds and minutes to 00:00.00 (mm:ss.SS)... How can I..? </p>
  
  <p>I have already asked this in SO in the following link.. <a href="https://stackoverflow.com/questions/10257330/nstimer-in-objective-c">NSTimer Decrease the time by seconds/milliseconds</a></p>
  
  <p>I i follow that code the time is not calculating (in the background also) when i drag and hold the scroll view with out releasing the mouseClick... Help me with the changes in below code...</p>
  
  <pre><code>enter code here
  @interface ViewController : UIViewController
  {
      IBOutlet UILabel *time;
      NSTimer *stopWatchTimer;
      NSDate *startDate;
      NSTimeInterval secondsAlreadyRun;
  }
  
  - (void)reset:(id)sender;
  - (void)onStartPressed:(id)sender; 
  - (void)onStopPressed:(id)sender;
  
  
  enter code here
  -(void)showActivity:(NSTimer *)tim 
  {
      NSDate *currentDate = [NSDate date];
  
      NSTimeInterval timeInterval = [currentDate timeIntervalSinceDate:startDate];
      // Add the saved interval
      timeInterval += secondsAlreadyRun;
      NSDate *timerDate = [NSDate dateWithTimeIntervalSince1970:timeInterval];
      static NSDateFormatter * dateFormatter = nil;
      if( !dateFormatter ){
          dateFormatter = [[NSDateFormatter alloc] init];
          [dateFormatter setDateFormat:@"mm:ss.SS"];
          [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];
      }
      NSString *timeString=[dateFormatter stringFromDate:timerDate];
      time.text = timeString;
  
      //    [dateFormatter release];
  }
  
  - (void)onStartPressed:(id)sender 
  {
      stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1/10 
                                                        target:self 
                                                      selector:@selector(showActivity:) 
                                                      userInfo:nil 
                                                       repeats:YES];
      // Save the new start date every time
      startDate = [[NSDate alloc] init]; // equivalent to [[NSDate date] retain];
      [stopWatchTimer fire];
  }
  
  - (void)onStopPressed:(id)sender
  {
      // _Increment_ secondsAlreadyRun to allow for multiple pauses and restarts
      secondsAlreadyRun += [[NSDate date] timeIntervalSinceDate:startDate];
      [stopWatchTimer invalidate];
      stopWatchTimer = nil;
  
      //    [startDate release];
      //    [self showActivity:stopWatchTimer];
  }
  </code></pre>