Actionbutton shown only when Selectinput changes

Question

Is there a way to show the actionbutton in shiny only when Selectinput changes? For example assume I have selected choice A from selectinput. At this point the actionbutton will be disabled, but as soon as I add choice B in addition to A(and vice versa when you delete choice B), the action button will show again to confirm these changes? I apologise in advance for not providing a reproducible example because I did not know how to approach it.

Answer 1

Perhaps you are looking for this

ui <- fluidPage(
    sidebarLayout(
      sidebarPanel(
        selectInput("actionona", "actionbutton on demand", c("A", "B"), selected=1),
        selectInput("actiondisableb", "Disable When D is selected", c("C", "D")),
        fluidRow( uiOutput("action1"), uiOutput("action2"))
      ),

      mainPanel(
        uiOutput('myvalue1'),
        uiOutput('myvalue2')
      )
    )
)

server <- function(input, output, session){
  
  output$action1 <-  renderUI({
    if(input$actionona=="A"){
      actionBttn(inputId="plotbtn", 
                 label="Action One",
                 style = "simple",
                 color = "success",
                 size = "md",
                 block = FALSE,
                 no_outline = TRUE
      )
    }else{
      return(NULL)
    }
    
  })
  
  output$action2 <-  renderUI({
    req(input$actiondisableb)
    if (is.null(input$actiondisableb)) {
      return(NULL)
    }
    else {
      actionBttn(inputId="plotmebtn", 
                 label="Action Two",
                 style = "simple",
                 color = "primary",
                 size = "md",
                 block = FALSE,
                 no_outline = TRUE
      )
    }
  })
  
  observeEvent(input$plotbtn, {
    req(input$plotbtn)
    if (input$plotbtn==0) {
      return(NULL)
    }else {
      output$myvalue1 <- renderUI({
        if (input$actionona=="A") {
          tagList(
            p("Blah Blah Blah 1", style = "color:red")
          )
          
        }else {return(NULL)}
      })
    }
    
  })
  
  observeEvent(input$plotmebtn, {
    req(input$actiondisableb,input$plotmebtn)
    if (input$plotmebtn==0) {
      return(NULL)
    }else {
      output$myvalue2 <- renderUI({
        if (input$actiondisableb=="C") {
          tagList(
            p("Blah Blah Blah 2", style = "color:blue")
          )
        }else {return(NULL)}
      })
    }
    
  })
  
}

shinyApp(ui = ui, server = server)