show UIPageControl only scrolling

ScrollViewDelegate.h

#import <UIKit/UIKit.h>

@interface ScrollViewDelegate : UIView <UIScrollViewDelegate> {
    UIPageControl *pageControl;
    NSTimer *updateTimer;
}

- (void)switchStateHidden;

@end

ScrollViewDelegate.m

#import "ScrollViewDelegate.h"

@implementation ScrollViewDelegate

- (id)initWithFrame:(CGRect)frame {
      self = [super initWithFrame:frame];
      pageControl = [[UIPageControl alloc] initWithFrame:frame];
      pageControl.userInteractionEnabled = NO;
      [self addSubview:pageControl];
//    pageControl.alpha = 0.0;
      return self;
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    pageControl.alpha = 1.0;
    if ([updateTimer isValid]) {
        [updateTimer invalidate];
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    pageControl.currentPage = self.currentPage;

    if (!updateTimer) {
        updateTimer = [[NSTimer alloc] initWithFireDate:[NSDate dateWithTimeIntervalSinceNow:1.0] interval:0 target:self selector:@selector(switchStateHidden) userInfo:nil repeats:NO];
    } else if (![updateTimer isValid]) {
        [updateTimer release];
        updateTimer = [[NSTimer alloc] initWithFireDate:[NSDate dateWithTimeIntervalSinceNow:1.0] interval:0 target:self selector:@selector(switchStateHidden) userInfo:nil repeats:NO];
    }
    [[NSRunLoop mainRunLoop] addTimer:updateTimer forMode:NSRunLoopCommonModes];

}

- (void)switchStateHidden {
    [UIView animateWithDuration:0.5 animations:^{ pageControl.alpha = 0.0; }];
}

@end