预览时，下载次数不累加

app/controllers/attachments_controller.rb

@@ -68,6 +68,7 @@ class AttachmentsController < ApplicationController
   end
 
   def direct_download
+    @attachment.increment_download
     send_file @attachment.diskfile, :filename => filename_for_content_disposition(@attachment.filename),
       :type => detect_content_type(@attachment),
       :disposition => 'attachment'    #inline can open in browser
@@ -78,7 +79,6 @@ class AttachmentsController < ApplicationController
     # 下载添加权限设置
     candown = attachment_candown @attachment
     if candown || User.current.admin? || User.current.id == @attachment.author_id
-      @attachment.increment_download
       if stale?(:etag => @attachment.digest)
         if params[:preview] == 'true'
           convered_file = @attachment.diskfile