Busy indicator when switch tabs? Should not!

server.R

shinyServer(function(input, output) {

  output$hist1 <- renderPlot({
      n <- (input$obs)
      dist <- NULL
      for (i in 1:n) {
        dist <- c(dist, rnorm(1))
      }
      hist(dist,main = paste("hist1", n), breaks = 100)

  })
  
  output$hist2 <- renderPlot({
      n <- (input$obs)
      dist <- NULL
      for (i in 1:n) {
        dist <- c(dist, rnorm(1))
      }
      hist(dist,main = paste("hist2", n), breaks = 100)

  })
  
})

ui.R

shinyUI(bootstrapPage(
  # Add custom CSS & Javascript;
  tagList(
    tags$head(
      tags$link(rel="stylesheet", type="text/css",href="style.css"),
      tags$script(type="text/javascript", src = "busy.js")
    )
  ),
  
  div(class = "busy",  
      p("Calculation in progress..")
      #, 
      #img(src="ajaxloaderq.gif")
  ),

  div(class = "span4",     
      sliderInput("obs", "Number of observations:",
                  min = 10000, max = 90000,
                  value = 20000, step = 10000)
  ),
  HTML('<ul class="nav nav-tabs">
          <li class=""><a onclick= "showMe(\'#hist1\')" >Tab1</a></li>
          <li class=""><a onclick= "showMe(\'#hist2\')" >Tab2</a></li>
        </ul>'),
  div(class = "output", 
      div(class = "tabSet",
        plotOutput('hist1'),
        plotOutput('hist2')
      )
  )
  
))

www\busy.js

var i = 99;
setInterval(function(){
  if (i == 99) {
    if ($("div img").length > 1) {
      $("div.tabSet > div").not("#hist1").hide();
      i = 0;
    }
}}, 10)
  
function showMe(id) {
  $("div.tabSet > div").not(id).hide(); $(id).show();
}


setInterval(function(){
  if ($('html').attr('class')=='shiny-busy') {
    $('div.busy').show()
  } else {
    $('div.busy').hide()
  }
},100)

www\style.css

div.busy { 
  position:absolute;
  top: 40%;
  left: 50%;
  margin-top: -100px;
  margin-left: -50px;
  display:none;
  background: rgba(200, 200, 200, .8);
  text-align: center;
  padding-top: 20px;
  padding-left: 30px;
  padding-bottom: 40px;
  padding-right: 30px;
  border-radius: 5px;
}

body {
  margin:1cm;
  font-size: 12px;
}

div.output {
  overflow-y:hidden;
}

ul.nav-tabs {
  overflow-y:hidden;
}