CCControlSlider setBackgroundSprite setProgressSprite setThumbSprite issue

hi guys,
i am trying to use cocos2dx 2.1.1 CCControlSlider and have a problem.
reproduce procedure:

  1. create a CCControlSlider by sprite frame
  2. after it is created successfully, invoke its setBackgroundSprite setProgressSprite setThumbSprite to use new sprite for background, progress and thumb
  3. the result is that new sprite is not displayed

i check CCControlSlider and found that setBackgroundSprite setProgressSprite setThumbSprite only retain the new sprite, but not add it in slider as child node.
is it the bug of CCControlSlider