Read only indicator in Shiny? - r

Question

I have an existing Shiny script with standard widgets from the Shiny library. Now I wish to add something to show temperature on a graphical scale? This would be a read-only value, so it wouldn't make sense to use a slider unless the slider can be locked and only changed programatically. Is that possible? If not, what are other suggestions?
To clarify:
Is it possible to have a Shiny slider as read only. The user can not slide it but it can be programmatically changed. Here is a Shiny slider:
library(shiny)
ui <- fluidPage(
sliderInput("aa", "Temp",
min = -20, max = 20,
value = 10, step = 10)
)
server <- function(input, output) { }
shinyApp(ui, server)
I'm not familiar with Shiny Dashboard but I saw taskItem. Can these be "dropped in" and used with a normal Shiny app that uses fluidPage, sidebarPanel, mainPanel? How does one remove the bullet point and the percentage? Here is an example of a taskItem.
library(shiny)
library(shinydashboard)
ui <- dashboardPage(
dashboardHeader(),
dashboardSidebar(),
dashboardBody(
taskItem(value = temp <- 89, color = "red",
"Temp"
))
)
server <- function(input, output) { }
temp <- 89
shinyApp(ui, server)

Answer 1

AFAIK, sliderInput cannot be used as an output. However here's a potential solution using progressBar from shinyWidgets package
library(shiny)
library(shinyWidgets)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
h3("Sidebar")
),
mainPanel(
br(), br(), br(),
progressBar("tempbar", value = 0, title = "Temperature", status = "danger")
)
)
)
server <- function(input, output, session) {
temp <- 89
updateProgressBar(session, id = "tempbar", value = temp)
}
shinyApp(ui, server)
shiny app with temperature bar
Replace temp in server with whatever calculated value you might have. For fixed temperature value just set it in ui, no need to use updateProgressBar. By default progressBar is scaled from 0-100. To modify see documentation for it.

Answer 2

You can use updateSliderInput to achieve such an behaviour. Couple this with shinyjs::disabled and you get what you want. I would however look for a less hackish solution:
library(shiny)
library(shinyjs)
ui <- fluidPage(
## add style to remove the opacity effect of disabled elements
tags$head(
tags$style(HTML("
.irs-disabled {
opacity: 1
}")
)
),
useShinyjs(),
disabled(sliderInput("aa", "Temp",
min = -20, max = 20,
value = 10, step = 10)),
actionButton("Change", "Change")
)
server <- function(input, output, session) {
observeEvent(input$Change, {
new_temp <- sample(seq(-20, 20, 10), 1)
updateSliderInput(session, "aa", value = new_temp)
})
}
shinyApp(ui, server)