Use renderUI to call a dashboardPage in shiny

Question

In http://shiny.rstudio.com/articles/dynamic-ui.html, it shows how to use renderUI to call UI function in server; but it doesn't work for dashboardpage. I guess the problem stays at the class of dashboardpage while renderUI generates a different class of object??? could this problem be fixed?

I used these codes to test renderUI on dashboardpage:

shinyApp(
  ui<-(uiOutput("x",replace=T)),
server<-function(input,output){
  output$x<-
    renderUI(dashboardPage(
    dashboardHeader(),
    dashboardSidebar(),
    dashboardBody()
  ))
})