閃亮的條件面板

Question

在我的應用中，我希望用戶選擇一個文件夾，然后從中選擇一個文件。

我以為可以使用conditionalPanel()以便用戶在選擇文件夾之前只能看到第一個按鈕。 我編寫了這段代碼，但收到了此錯誤消息，“未找到對象'輸入'”，這樣做的正確方法是什么？ 將條件面板置於絕對面板中是否有問題？

library(shiny)
library(ggplot2)

ui <- shinyUI(fluidPage(
  titlePanel(""),
  fluidRow(
    # select input for selecting a folder
    column(2, absolutePanel(fixed = TRUE, width = '180px',
                      selectInput("pick_folder", label = '', selected='choose_a_folder',
                              choices = setNames(as.list(c('choose_a_folder', basename(setdiff(list.dirs(recursive = FALSE),'.')))), 
                                                 c('choose_a_folder', basename(setdiff(list.dirs(recursive = FALSE),'.'))))))),
    # select input for selecting a file absolutePanel then conditionalPanel
    column(2, absolutePanel(fixed = TRUE, width = '180px', 
                      conditionalPanel(condition="input.pick_folder==choose_a_folder",
                                 selectInput('pick_file', label = '', selected = 'choose_a_file',
                                           choices = setNames(as.list(c('choose_a_file', basename(setdiff(list.files(path=input$pick_folder ,recursive = FALSE),'.')))), 
                                                              c('choose a file', basename(setdiff(list.files(path=input$pick_folder ,recursive = FALSE),'.')))))))),
  ),
  fluidRow(
    #plot
    plotOutput('my_plot')

    )))

  # server
  server <- shinyServer(function(input, output) {
    output$my_plot <- renderPlot({
      dat <- read.table(file=paste(input$pick_folder, input$pick_file, sep='/'))
      # some plots over dat
    })

  })
  shinyApp(ui, server)

Answer 1

探查來自嘗試在應用程序的ui部分內部動態創建文件選擇的選擇。 您應該執行的方法是使用uiOutput和renderUI在server部分中創建ui的動態部分（您的文件選擇）

以下代碼似乎可以滿足您的描述：

library(shiny)
library(ggplot2)

ui <- shinyUI(fluidPage(
  titlePanel(""),
  fluidRow(
    # select input for selecting a folder
    column(2, absolutePanel(fixed = TRUE, width = '180px',
                            selectInput("pick_folder", label = '', selected='choose_a_folder',
                                        choices = setNames(as.list(c('choose_a_folder', basename(setdiff(list.dirs(recursive = FALSE),'.')))), 
                                                           c('choose_a_folder', basename(setdiff(list.dirs(recursive = FALSE),'.'))))))),
    # select input for selecting a file absolutePanel then conditionalPanel
    column(2, absolutePanel(fixed = TRUE, width = '180px', 
                            conditionalPanel(condition="input.pick_folder==choose_a_folder",
                                             # Insert a dynamic bit of UI
                                             uiOutput("fileselection") 
                                             )
                            )
           )
  ),
  fluidRow(
    #plot
    plotOutput('my_plot')

  )))

# server
server <- shinyServer(function(input, output) {
  output$my_plot <- renderPlot({
    dat <- read.table(file=paste(input$pick_folder, input$pick_file, sep='/'))
    # some plots over dat
  })

  output$fileselection <- renderUI({  #Define the dynamic UI
    selectInput('pick_file', label = '', selected = 'choose_a_file',
                choices = setNames(as.list(c('choose_a_file', basename(setdiff(list.files(path=input$pick_folder ,recursive = FALSE),'.')))), 
                                   c('choose a file', basename(setdiff(list.files(path=input$pick_folder ,recursive = FALSE),'.'))
                                   )
                )
    )
  })

})

shinyApp(ui, server)