使用UIImagePickerController和UIPopoverController两次内存泄漏

- (IBAction)selectExistingPicture 
{  
 if ([UIImagePickerController isSourceTypeAvailable: UIImagePickerControllerSourceTypePhotoLibrary]) 
 { 
  UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
  imagePicker.delegate = self;
  imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

  UIPopoverController *popVC = [[UIPopoverController alloc] initWithContentViewController: imagePicker];
  popVC.delegate = self; 
  [popVC setPopoverContentSize:CGSizeMake(320, 100)];
  [popVC presentPopoverFromRect:CGRectMake(39, 356, 320, 100) inView:self.view permittedArrowDirections:1 animated:NO];
 }
 else 
 {
  UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error accessing photo library"
              message:@"Device does not support a photo library" delegate:nil
             cancelButtonTitle:@"Cancel" otherButtonTitles:nil]; 
  [alert show]; 
  [alert release];
 }
}