Modify shiny action button once it is clicked

问题:

I have the following in server.R

shinyServer(function(input, output) {

# 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# when the value of input$goButton becomes out of date 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()
})
})

and the following in ui.R

shinyUI(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.")
),
mainPanel(
verbatimTextOutput("nText")
)
))

My goal is to make the go action button disappear once it is clicked five times and give a pop up window warning if clicked less than five times.

回答1:

As @daattali is saying, shinyjs make this really easy, you can do it like this:

library(shiny)
library(shinyjs)

ui <- shinyUI(
  fluidPage(
    useShinyjs(),
    sidebarPanel(
      actionButton('btn','Click me')
    ),
    mainPanel(
      verbatimTextOutput("nText")
    )
  )
)

server <- shinyServer(function(input,output,session){
  n <- 0
  makeReactiveBinding('n')

  observeEvent(input$btn, { 
    if(n < 5){
      info('Msg')
    } else if(n > 5){
      hide('btn')
    }
    n <<- n + 1 
  })

  output$nText <- renderText({
    n
  })

})

shinyApp(ui=ui,server=server)

Here's how you would hide the button without using shinyjs:

library(shiny)

ui <- shinyUI(
  fluidPage(
    tags$head(
      tags$style(
        HTML('#num{display: none;}')
      )
    ),
    useShinyjs(),
    sidebarPanel(
      conditionalPanel(
        condition = "input.num < 5",
        actionButton('btn','Click me')
      ),
      numericInput('num','',0)
    ),
    mainPanel(
      verbatimTextOutput("nText")
    )
  )
)

server <- shinyServer(function(input,output,session){
  n <- 0
  makeReactiveBinding('n')

  observeEvent(input$btn, { 
    n <<- n + 1
    updateNumericInput(session,'num',value=n)
  })

  output$nText <- renderText({
    n
  })

})

shinyApp(ui=ui,server=server)

And finally without using observeEvent:

library(shiny)

ui <- shinyUI(
  fluidPage(
    tags$head(
      tags$style(
        HTML('#num{display: none;}')
      )
    ),
    useShinyjs(),
    sidebarPanel(
      conditionalPanel(
        condition = "input.num < 5",
        actionButton('btn','Click me')
      ),
      numericInput('num','',0)
    ),
    mainPanel(
      verbatimTextOutput("nText")
    )
  )
)

server <- shinyServer(function(input,output,session){
  n <- 0
  makeReactiveBinding('n')

  observe({
    input$btn
    isolate({
      n <<- n + 1
      updateNumericInput(session,'num',value=n)
    })
  })

  output$nText <- renderText({
    n
  })

})

shinyApp(ui=ui,server=server)

回答2:

You don't need to define a reactive n. It is already the value of input$btn.

library(shiny)
library(shinyjs)

ui <- shinyUI(
  fluidPage(
    useShinyjs(),
    sidebarPanel(
      actionButton('btn','Click me')
    ),
    mainPanel(
      verbatimTextOutput("nText")
    )
  )
)

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

  observe({ 
    if(input$btn < 5){
      info('Msg')
    } else {
      hide('btn')
    }
  })

  output$nText <- renderText({
    input$btn
  })

})

shinyApp(ui=ui,server=server)