content: function init()
      m.category_list=m.top.findNode("category_list")
      m.category_list.setFocus(true)
  	m.top.observeField("visible", "onVisibleChange")
  end function
  
  sub onVisibleChange()
  	if m.top.visible = true then
  		m.category_list.setFocus(true)
  	end if
  end sub
  
  function updateConfig(params)
      categories = params.config.categories
      contentNode = createObject("roSGNode","ContentNode")
      for each category in categories
          node = createObject("roSGNode","category_node")
          node.title = category.title
          node.feed_url = params.config.host + category.feed_url
          contentNode.appendChild(node)
      end for
      m.category_list.content = contentNode
  end function