How can I make the modal dialog show up after the first click of the actionButton?

edit

You can achieve this by adding an observeEvent function that triggers the modal dialog to show up after the first click of the actionButton. Here's an example code:

library(shiny)

ui <- fluidPage(
  actionButton("btn", "Click me"),
  fluidRow(
    column(12,
           tags$div(id = "modalExample", class = "modal fade",
                    tags$div(class = "modal-dialog",
                             tags$div(class = "modal-content",
                                      tags$div(class = "modal-header",
                                               tags$h5(class = "modal-title", "Modal Title"),
                                               tags$button(type = "button", class = "close", "×", 
                                                           data_dismiss = "modal", 
                                                           aria_label = "Close")),
                                      tags$div(class = "modal-body",
                                               tags$p("This is the modal body text."))
                             )
                    )
           )
    )
  )
)

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

  observeEvent(input$btn, {
    if (input$btn == 1) {
      showModal("modalExample")
    }
  })

}

shinyApp(ui, server)

In this code, we added an observeEvent function that listens to the click of the actionButton. If the button is clicked for the first time (input$btn == 1), then the showModal function is called to trigger the modal dialog to show up.