Update label of actionButton in shiny - r

Question

I know that similar question was already answered, however the solution creates a new actionButton with different label upon string-input. What I need is to keep the button(the counter of the button), because when I change the label and create a new button it has a counter of 0(not clicked).
So basically I need something like an update function to just change the label of the actionButton, when it is pressed. You press it once and the label changes.
input$Button <- renderUI({
if(input$Button >= 1) label <- "new label"
else label <- "old label"
actionButton("Button", label = label)
})
Something like this, but without reseting the value of the button(by creating a whole new one).
Thanks!

Answer 1

reactiveValues() can help. Check http://shiny.rstudio.com/articles/reactivity-overview.html for details.
In the following example, I renamed your input$Button to input$click to avoid double usage of the "Button" name.
Since we wrap the label in a renderUI(), input$click initially fires once it is created?!?, that's why I put the label
condition as: if(vars$counter >= 2)
An alternative solution could be to remove the read-only attribute (found here: https://github.com/rstudio/shiny/issues/167)
attr(input, "readonly") <- FALSE
input$click <- 1
For an example
paste the following in your R console:
ui <- bootstrapPage(
uiOutput('Button')
)
server <- function(input, output) {
# store the counter outside your input/button
vars = reactiveValues(counter = 0)
output$Button <- renderUI({
actionButton("click", label = label())
})
# increase the counter
observe({
if(!is.null(input$click)){
input$click
isolate({
vars$counter <- vars$counter + 1
})
}
})
label <- reactive({
if(!is.null(input$click)){
if(vars$counter >= 2) label <- "new label"
else label <- "old label"
}
})
}
# run the app
shinyApp(ui = ui, server = server)

Answer 2

You can use updateActionButton from native shiny package:
ui <- fluidPage(
actionButton('someButton', ""),
h3("Button value:"),
verbatimTextOutput("buttonValue"),
textInput("newLabel", "new Button Label:", value = "some label")
)
server <- function(input, output, session) {
output$buttonValue <- renderPrint({
input$someButton
})
observeEvent(input$newLabel, {
updateActionButton(session, "someButton", label = input$newLabel)
})
}
shinyApp(ui, server)

Answer 3

A few years later some small addition: If you want to switch between button icons, e.g. play / pause button (and switching between labels would be similar) you could do something like this (based on shosaco's answer).
library(shiny)
ui <- fluidPage(
fluidRow(
actionButton("PlayPause", NULL, icon = icon("play"))
)
)
server <- function(input, output, session) {
# whenever the ActionButton is clicked, 1 is added to input$PlayPause
# check if input$PlayPause is even or odd with modulo 2
# (returns the remainder of division by 2)
observeEvent(input$PlayPause, {
if (input$PlayPause %% 2 != 0) {
updateActionButton(session, "PlayPause", NULL, icon = icon("pause"))
} else {
updateActionButton(session, "PlayPause", NULL, icon = icon("play"))
}
})
}
shinyApp(ui = ui, server = server)