R shiny - last clicked button id

Question

I have multiple action buttons, on which i want to show different select Inputs and I want to know last clicked button id, how can I do that? When I use

whic         


        

Answer 1

This code track which button was last clicked:

   library(shiny)


    ui <- shinyUI(fluidPage(


       titlePanel("Track last clicked Action button"),


       sidebarLayout(
          sidebarPanel(
            actionButton("first", "First"),
            actionButton("second", "Second"),
            actionButton("third", "Third")
          ),

          # Show a plot of the generated distribution
          mainPanel(
             textOutput("lastButtonCliked")
          )
       )
    ))


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

            rv <- reactiveValues(lastBtn = character())
            observeEvent(input$first, {
                    if (input$first > 0 ) {
                            rv$lastBtn = "first"
                    }
            })
            observeEvent(input$second, {
                    if (input$second > 0 ) {
                            rv$lastBtn = "second"
                    }
            })
            observeEvent(input$third, {
                    if (input$third > 0 ) {
                            rv$lastBtn = "third"
                    }
            })
            output$lastButtonCliked <- renderText({
                    paste("Last button clicked: ", rv$lastBtn)
            })
    })
    # Run the application 
    shinyApp(ui = ui, server = server)

Version with lapply with many buttons. Credit goes to @Victorp and this answer.

This is the code:

    library("shiny")
    ui <- fluidPage(
            fluidRow(
                    column(
                            width = 6,
                            lapply(
                                    X = 1:5,
                                    FUN = function(i) {
                                            actionButton(inputId = paste0("button", i), label = paste("Button ", i))
                                    }
                            )
                    ),
                    column(
                            width = 6,
                            textOutput("lastButtonCliked")
                    )
            )
    )
    server <- function(input, output){

            rv <- reactiveValues(lastBtn = character())

            lapply(
                    X = 1:6,
                    FUN = function(i){
                            observeEvent(input[[paste0("button", i)]], {
                                    if (input[[paste0("button", i)]] > 0) {
                                            rv$lastBtn = paste0("button", i)    
                                    }
                            })
                    }
            )

            output$lastButtonCliked <- renderText({
                    paste("Last button clicked: ", rv$lastBtn)
            })
    }
    shinyApp(ui = ui, server = server)