R Shiny: refreshing/overriding actionButton() output - r

Question

I am trying to adapt R Shiny: automatically refreshing a main panel without using a refresh button to a new minimal working example:
ui <- fluidPage(
pageWithSidebar(
headerPanel("actionButton test"),
sidebarPanel(
numericInput("n", "N:", min = 0, max = 100, value = 50),
br(),
actionButton("goButton", "Go!"),
p("Click the button to update the value displayed in the main panel."),
actionButton("newButton", "New Button"),
actionButton("newButton2", "Another New Button")
),
mainPanel(
verbatimTextOutput("nText"),
textOutput("some_text_description"),
plotOutput("some_plot")
)
)
)
server <- function(input, output, session) {
# builds a reactive expression that only invalidates
# when the value of input$goButton becomes out of date
# (i.e., when the button is pressed)
ntext <- eventReactive(input$goButton, {
input$n
})
output$nText <- renderText({
ntext()
})
# Prep some text for output
output$some_text_description <- renderText({
if (input$newButton == 0) {return(NULL)}
else {
"Lorem ipsum dolorom."
}
})
# Prep some figure for output
# Simple Bar Plot
output$some_plot <- renderPlot({
if (input$newButton2 == 0) {return(NULL)}
else {
counts <- table(mtcars$gear)
barplot(counts, main="Car Distribution", xlab="Number of Gears")
}
})
}
shinyApp(ui = ui, server = server)
In the code above, I have three actionButton commands, one which produces a plot, one which produces text output, and one which produces a number (as verbatim text output). As you click through each button, new output appears alongside previously generated output (from the last button you pressed).
Without needing to implement a refresh button that clears everything manually, how do I get each actionButton to override (i.e., wipe) the output of the others automatically without them all stacking atop of each other in the main panel. My understanding is that I need to use some combination of observeEvent, NULL, and reactiveValues but my attempts have so far been unsuccessful.

Answer 1

You can use renderUI() for that.
output$all <- renderUI({
global$out
})
Within a global reactiveValue global$out you can store which ui element you would like to display. (Initially it should be empty, therefore NULL).
global <- reactiveValues(out = NULL)
And then listen for the clicks in the Buttons and update global$out accordingly.
observeEvent(input$goButton, {
global$out <- verbatimTextOutput("nText")
})
observeEvent(input$newButton, {
global$out <- textOutput("some_text_description")
})
observeEvent(input$newButton2, {
global$out <- plotOutput("some_plot")
})
Full app would read:
library(shiny)
ui <- fluidPage(
pageWithSidebar(
headerPanel("actionButton test"),
sidebarPanel(
numericInput("n", "N:", min = 0, max = 100, value = 50),
br(),
actionButton("goButton", "Go!"),
p("Click the button to update the value displayed in the main panel."),
actionButton("newButton", "New Button"),
actionButton("newButton2", "Another New Button")
),
mainPanel(
uiOutput("all")
)
)
)
server <- function(input, output, session) {
global <- reactiveValues(out = NULL)
observeEvent(input$goButton, {
global$out <- verbatimTextOutput("nText")
})
observeEvent(input$newButton, {
global$out <- textOutput("some_text_description")
})
observeEvent(input$newButton2, {
global$out <- plotOutput("some_plot")
})
output$all <- renderUI({
global$out
})
output$nText <- renderText({
input$n
})
output$some_text_description <- renderText({
"Lorem ipsum dolorom."
})
# Simple Bar Plot
output$some_plot <- renderPlot({
counts <- table(mtcars$gear)
barplot(counts, main="Car Distribution", xlab="Number of Gears")
})
}
shinyApp(ui = ui, server = server)