Shiny and shinydashboard: How to display inputs in sidebar only on certain tabs?

Question

I want to display inputs (checkboxes, select input) in the sidebar of my shiny dashboard, but only when a certain tab is clicked.

Minimum reporducible example below. How can I get the checkboxes and select input to only show up when on Page 2?

#ui.R

library(shiny)
library(shinydashboard)

# Define UI for application that draws a histogram
shinyUI(dashboardPage(
    dashboardHeader(title = "Test Application",
                    titleWidth = "400px"
    ),

    dashboardSidebar(
        id = "navbar",
        menuItem("Page 1", tabName = "page1"),
        menuItem("Page 2", tabName = "page2"),

        # THESE SHOW UP ALL THE TIME - HOW TO GET JUST ON PAGE 2?
        checkboxGroupInput("outcome", "Select Outcome Variable(s):", choices = c("Box 1", "Box 2", "Box 3")),
        selectInput("selectinput", label = "Select:", choices = c("Choice 1", "Choice 2", "Choice 2"))


    ),

    dashboardBody(
        tabItems(
            tabItem(
                tabName = "page1",
                h1("This is page 1")
            ),

            tabItem(
                tabName = "page2",
                h1("This is page 2")
            )
        )
    )
))

I assume something is needed in here to make the inputs dynamic?

# server.R

library(shiny)

# Define server logic required to draw a histogram
shinyServer(function(input, output) {
})

Answer 1

ANSWER: use a conditional panel that queries the selected tab.

Credit: Mine at Rstudio

library(shiny)
library(shinydashboard)

# ui ---------------------------------------------------------------------------

ui <- dashboardPage(

  # title ----
  dashboardHeader(title = "Test Application"),

  # sidebar ----
  dashboardSidebar(
    sidebarMenu(id = "sidebarid",
                menuItem("Page 1", tabName = "page1"),
                menuItem("Page 2", tabName = "page2"),
                conditionalPanel(
                  'input.sidebarid == "page2"',
                  sliderInput("bins", "Number of bins:", min = 1, max = 50, value = 30),
                  selectInput("title", "Select plot title:", choices = c("Hist of x", "Histogram of x"))
                )
    )
  ),

  # body ----
  dashboardBody(
    tabItems(
      # page 1 ----
      tabItem(tabName = "page1", "Page 1 content. This page doesn't have any sidebar menu items."),
      # page 2 ----
      tabItem(tabName = "page2", 
              "Page 2 content. This page has sidebar meny items that are used in the plot below.",
              br(), br(),
              plotOutput("distPlot"))
    )
  )
)

# server -----------------------------------------------------------------------

server <- function(input, output, session) {

  output$distPlot <- renderPlot({
    x    <- faithful[, 2]
    bins <- seq(min(x), max(x), length.out = input$bins + 1)
    hist(x, breaks = bins, col = "darkgray", border = "white", main = input$title)
  })

}

# shiny app --------------------------------------------------------------------

shinyApp(ui, server)