Shiny: Show Download Button Only If An Action Button Is Pressed - r

Question

I have a reactive data frame df1(). A user can add their initials as text inputs such that the text is filled to rows as a new column name when the user clicks the Add button.
Everything works fine but I would like to add one more thing:
Make the download button download show only if the action button bttn1 is pressed. Currently download is shown regardless of pressing bttn1.
I can't understand why the following is not working:
observe({
if (is.null(input$bttn1)) {shinyjs::hide("download")}
else {shinyjs::show("download")}
})
The following is a fully working code:
##### ui
ui <- dashboardPage(
skin = "black",
#### Upper navigation bar
dashboardHeader(
title = "title",
titleWidth = 230
),
#### Side bar
dashboardSidebar(disable = T),
#### Body
dashboardBody(
shinyjs::useShinyjs(),
tabsetPanel(
tabPanel(
### tab1
tabName = "tab1",
h5("Tab 1"),
fluidRow(
reactableOutput("table1"),
textInput("textinput1", "Initials:"),
actionButton("bttn1", "Add", class = "btn-primary"),
reactableOutput("table2"),
uiOutput("ui_download")
) # fluidRow
), # tabPanel
#### tab2
tabPanel(
tabName = "tab2",
h5("Tab 2"),
fluidRow(
) # fluidRow
) # tabPanel
) # tabsetPanel
) # dashboardBody
) # dashboardPage
#### server
server <- function(input, output, session) {
## df1
# reactive
df1 <- reactive({
data.frame(
"id" = c("A", "A", "A", "A"),
"num1" = c(10, 11, 12, 13)
)
})
# renderReactable
output$table1 <- renderReactable({
reactable(df1(), borderless = F, defaultColDef = colDef(align = "center"))
})
## df2
## Text input
rv1 <- reactiveValues()
observe({
if (nrow(df1()) == 0) {shinyjs::hide("bttn1")}
else {shinyjs::show("bttn1")}
})
observe({
if (nrow(df1()) == 0) {shinyjs::hide("textinput1")}
else {shinyjs::show("textinput1")}
})
observeEvent(input$bttn1, {
rv1$values <- df1()
rv1$values$name <- input$textinput1
})
rv1_text <- reactive({
rv1$values
})
output$table2 <- renderReactable({
req(rv1_text())
reactable(rv1_text(), borderless = F, defaultColDef = colDef(align = "center"))
})
## downloadButton
# renderUI
output$ui_download <- renderUI({
# req(rv1_text())
downloadButton("download", "Download")
})
**# Why isn't this working?**
observe({
if (is.null(input$bttn1)) {shinyjs::hide("download")}
else {shinyjs::show("download")}
})
# Download csv
output$download <- downloadHandler(
filename = function() {
paste0('data', '.csv')
},
content = function(file) {
write.csv(rv1_text(), file, row.names = F)
}
)
}
shinyApp(ui, server)

Answer 1

I couldn't run your codes since you did not share the libraries you used in. But If I understand you correctly, conditionalPanel is very suitible for your purpose.
Here is a small shiny app that you can adapt it to your codes:
library(shiny)
ui <- fluidPage(
actionButton("call_download", "Show Download Button"),
conditionalPanel(condition = "input.call_download == 1",
downloadLink('downloadData', 'Download')
)
)
server <- function(input, output) {
output$downloadData <- downloadHandler(
filename = function() {
paste('data-', Sys.Date(), '.csv', sep='')
},
content = function(con) {
write.csv(mtcars, con)
} )
}
shinyApp(ui, server)