Stop dropdownButton (shinywidgets) from opening dialog in R shiny

Question

I'm looking to stop a dropdownbutton (shinywidgets) from opening when the button is clicked based on a condition. This to avoid renderUI errors on missing input for content on the dropdownButton modal panel.

When a user clicks on a dropdownButton, it normally opens a panel. In my case, this panel contains renderUIelements that depend on various variables. If these variables do not exist yet, the renderUIswill cause errors to spit out.

What I would like to know is whether there is a way to look at the click observeEvent(input$MydropdownButton, { ....}) and then completely stop it from opening the panel if a condition is not met, rather than toggle it to close immediately (not working version)

What I plan to do, is to give the user a sweetalert instead that informs the user of which options he has to create or load the needed data. And I know how to do the message, purely looking to stop the opening part in an 'if else' way

• I know I can use shinyjs::disable('MydropdownButton') inside an observer with ifstatement to block the use of the button, but this would not allow me to trigger the sweetalerton a click anymore
• I also know I can adjust all my renderUIs not to render if the needed input is missing, but by now there are a lot of renderUIs involved, and I'm:
  • A: afraid to make a mess of the code, and
  • B: eager to find out if there is a way in general to stop the opening of dropdownButtons

I've tried something like this:

observeEvent(input$MydropdownButton, { 
if(!is.null(values$neededData)) { 'just open the dropdownbutton' } 
else { toggleDropdownButton('TestDrop')
'run sweetalert code'} 
})

But the toggleDropdownButtonwill only close the dropdownButtonpanel once it's already triggered to open, and thus shiny tried to renderthe uielement, with the resulting error, rather than block it from opening.

Here are a full serverand uicode files to demonstrate it calling for non-existing numbers.

SERVER file

shinyServer = function(input, output, session) {

  values <- reactiveValues()

  output$Reset_Threshold <- renderUI({
    if(values$randomNr == 2) { actionButton(inputId = "Reset_Threshold", label = icon("undo")) }
    else if(values$randomNr == 1) { actionButton(inputId = "Reset_Threshold", label = icon("table"))  }
  })

  observeEvent(input$TestDrop, { 
    if(!is.null(values$randomNr )) { print('no problems')}
    else {  toggleDropdownButton('TestDrop') 
      # Run other code here to alert user.
    }
    })
}

UI file

library(shiny)
library(shinyWidgets)

    ui <- fluidPage(
      dropdownButton(inputId= "TestDrop", 
                     uiOutput('Reset_Threshold'),
                     icon = icon("table"), tooltip = tooltipOptions(title = "Click"))
      )

```

Answer 1

The error is not caused by toggling the dropdown menu but referencing a variable randomNr that doesn't exist. I added the variable and also a sweet dialog when the data is not ready in the server logic now it works.

But do note that it's not possible to stop the dropdown menu from opening. We still need to close it. If you want to block it from opening completely, you can conditionally render a regular Shiny actionButton when your data is not ready and will still trigger an event. Just make sure only one button is rendered under different condition and they should use the same input ID.

function(input, output, session) {
  values <- reactiveValues(Filter_df = NULL, randomNr = 0)

  output$Reset_Threshold <- renderUI({
    if (values$randomNr == 2) {
      actionButton(inputId = "Reset_Threshold", label = icon("undo"))
    }
    else if (values$randomNr == 1) {
      actionButton(inputId = "Reset_Threshold", label = icon("table"))
    }
  })

  observeEvent(input$TestDrop, {
    if (!is.null(values$Filter_df)) {
      print("no problems")
    } else {
      toggleDropdownButton("TestDrop")
      # Run other code here to alert user.
      sendSweetAlert(session, "data not ready")
    }
  })
}

EDIT

Just render a different button now. I'm using a single file app.R

library(shiny)
library(shinyWidgets)

ui <- fluidPage(
  uiOutput("button")
)

server <- function(input, output, session) {
  values <- reactiveValues(Filter_df = NULL, randomNr = 0)

  output$button <- renderUI({
    if (values$randomNr == 1) {
      dropdownButton(
        inputId = "dropdown",
        actionButton(inputId = "Reset_Threshold", label = icon("table")),
        icon = icon("table"), tooltip = tooltipOptions(title = "Click")
      )
    } else {
      actionButton(
        inputId = "alert",
        NULL,
        icon = icon("table")
      )
    }
  })

  observeEvent(input$alert, {
    sendSweetAlert(session, "data not ready")
  })
}

shiny::shinyApp(ui, server)