title: UITapGestureRecognizer
body: <p>I check out Apple's ScrollView suite example code. When i use it in my code then it not working while i had not made any change.I was just wondering how I cannot get a double tap to undo the zoom inside of a scroll view? I cant seem to figure it out. I am insert image from URL  while in the sample code drag a image in interface builder. I also try with same code but recognize of tap on image is not working. Why it happened i can not get it? I also show my code below:</p>
  
  <pre><code>- (void)loadView {
  [super loadView];
  
  // set the tag for the image view
  [imageView setTag:ZOOM_VIEW_TAG];
  
  // add gesture recognizers to the image view
  UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];
  UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
  UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTwoFingerTap:)];
  
  [doubleTap setNumberOfTapsRequired:2];
  [twoFingerTap setNumberOfTouchesRequired:2];
  
  [imageView addGestureRecognizer:singleTap];
  [imageView addGestureRecognizer:doubleTap];
  [imageView addGestureRecognizer:twoFingerTap];
  
  [singleTap release];
  [doubleTap release];
  [twoFingerTap release];
  
  NSURL *imgUrl=[[NSURL alloc] initWithString:@"http://www.iso.org/iso/alan_bryden_larger.jpg"];                 
  NSData *imgData = [NSData dataWithContentsOfURL:imgUrl];
  UIImage *img = [UIImage imageWithData:imgData];
  imageView = [[UIImageView alloc] initWithImage:img];
  
  [self.imageScrollView addSubview:imageView];
  [imgUrl release]; 
  
  // calculate minimum scale to perfectly fit image width, and begin at that scale
  float minimumScale = [imageScrollView frame].size.width  / [imageView frame].size.width;
  [imageScrollView setMinimumZoomScale:minimumScale];
  [imageScrollView setZoomScale:minimumScale];}
  - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
  return [imageScrollView viewWithTag:ZOOM_VIEW_TAG];} 
  
  
   - (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
  [scrollView setZoomScale:scale+0.01 animated:NO];
  [scrollView setZoomScale:scale animated:NO];}
  
   - (void)handleDoubleTap:(UIGestureRecognizer *)gestureRecognizer {
  // double tap zooms in
  float newScale = [imageScrollView zoomScale] * ZOOM_STEP;
  CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];
  [imageScrollView zoomToRect:zoomRect animated:YES];}
  
   - (void)handleTwoFingerTap:(UIGestureRecognizer *)gestureRecognizer {
  // two-finger tap zooms out
  float newScale = [imageScrollView zoomScale] / ZOOM_STEP;
  CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];
  [imageScrollView zoomToRect:zoomRect animated:YES];}
  </code></pre>