title: UIImageView images overlaps each other
body: <p>I have a small problem where I am trying to generate QR codes on user click which fetches string from the UITextField. Everything works good except one which is new UIImageView overlaps the other in spite of the fact that I am reinitializing it.</p>
  
  <p>he function:</p>
  
  <pre><code>- (void)showQR
  {
      if([textFieldRounded.text length] != 0 ){
          NSString* aVeryLongURL = textFieldRounded.text;
          DataMatrix* qrMatrix = [QREncoder encodeWithECLevel:QR_ECLEVEL_H version:QR_VERSION_AUTO string:aVeryLongURL];
          qrcodeImage = [QREncoder renderDataMatrix:qrMatrix imageDimension:qrcodeImageDimension];
          qrcodeImageView = [[UIImageView alloc] initWithImage:qrcodeImage];
          CGRect parentFrame = self.view.frame;
          CGRect tabBarFrame = self.tabBarController.tabBar.frame;
          CGFloat x = (parentFrame.size.width - qrcodeImageDimension) / 2.0;
          CGFloat y = (parentFrame.size.height - qrcodeImageDimension - tabBarFrame.size.height) / 2.0;
          y = y+75;
          CGRect qrcodeImageViewFrame = CGRectMake(x, y, qrcodeImageDimension, qrcodeImageDimension);
          [qrcodeImageView setFrame:qrcodeImageViewFrame];
          [self.view addSubview:qrcodeImageView];
          return;
      }
      else
      {
          UIAlertView *alert1 = [[UIAlertView alloc] initWithTitle:@"Warning" message:@"Enter the URL" delegate:nil cancelButtonTitle: @"OK" otherButtonTitles:nil];
          [alert1 show];
          return;
      }
  
  }
  </code></pre>
  
  <p>Each time user clicks on submit button which calls this function, a new QR overlaps the older one.</p>
  
  <p>I have my .h file where I declared</p>
  
  <pre><code>@property (atomic, strong)  UIImageView *qrcodeImageView;
  @property (atomic, strong)  UIImage* qrcodeImage;
  </code></pre>
  
  <p>synthesized in .m file too.</p>