code: public boolean clickOn(int index) {
  		ImageItem item = getItem(index);
  		if (item == null || TextUtils.isEmpty(item.mimeType)) {
  			return false;
  		}
  		// For non-image items, the first tap will start it downloading
  		if (!Util.isMimeTypeImage(item.mimeType)) {
  			// It is being downloaded, do nothing (prevent double tap, etc)
  			if (downloadItems.contains(item.originalPath)) {
  				return true;
  			} else {
  				// If no write permission, do not try to download. Instead let caller handles it by launching browser
  				if (!bHasWritePermission) {
  					return false;
  				}
  				File localFile = new File(item.localCachePath);
  				if (localFile.exists() && ApptentiveAttachmentLoader.getInstance().isFileCompletelyDownloaded(item.localCachePath)) {
  					// If have right permission, and already downloaded, let caller open 3rd app to view it
  					return false;
  				} else {
  					// First tap detected and never download before, start download
  					downloadItems.add(item.originalPath);
  					notifyDataSetChanged();
  					return true;
  				}
  			}
  		}
  		return false;
  	}
docs: Click an image
  
  @param index
  @return True if handled here; False, let the caller handle it, i.e. launch 3rd party app to open attachment