反应式 selectInput 选项和选定值无法正确重置为 NULL

Posted 2023-03-24

【中文标题】反应式 selectInput 选项和选定值无法正确重置为 NULL

【英文标题】：reactive selectInput choices and selected values cannot be reset to NULL correctly

【发布时间】：2017-10-20 03:46:14

【问题描述】：

在我的 Shiny 应用程序中，我会将input$columns 中选择的列弹出到input$vars，然后将input$vars 中的选择弹出到input$fromvars 以供进一步选择。但是，当我取消选择inut$columns 中的所有列时，我的代码无法正常工作（我用renderPrint 进行了测试，它显示input$columns 是“NULL”），因为我期望不仅input$vars 值是NULL（它可以工作)，而且这个selectInput中的选项也应该是NULL，下拉列表中没有任何内容可供选择，但是，我点击下拉列表，发现显示最后一个input$columns中的最后一个选择。

更糟糕的是input$fromvars，我希望它的值被重置为 NULL，因为 input$vars 被重置为 NULL（在input$columns 中的选择发生变化时），选择也应该被重置为 NULL，这样在下拉列表。但是，除非我手动更新input$vars，否则这不起作用。

请在下面找到我的代码，有人可以帮忙看看吗？

if(interactive()) 

ui <- fluidPage(

  sidebarLayout(
    sidebarPanel( 

      fileInput("file", "Choose CSV File",
                # limit the file extention to the following:
                accept=c("text/csv", 
                         "text/comma-separated-values,text/plain", 
                         ".csv")),

      h5("Upload file for data analysis"),


      # no choices before a file uploaded
      uiOutput("columns"),

      # inputs to generate pivot table (demo in a single tab here, but in real app, this will be on a different tab)
      selectInput("vars", "vars to use:", choices = NULL, multiple = TRUE, selected = NULL),
      selectInput("fromvars", "select from vars:", choices = NULL, multiple = TRUE, selected = NULL)

      ),

    mainPanel( 
      verbatimTextOutput("print")
    ))
)

server <- function(input, output, session) 

  dt <- reactiveValues()

  # upload file
  observeEvent(input$file, 
    inFile <- input$file
    req(inFile)
    # upload the file to dataset
    dt$data = read.csv(inFile$datapath, header = TRUE)
  )


  # create columns groupcheckbox ui
  output$columns <- renderUI(

    # get the col names of f and assign them to a list
    cols = mapply(list, names(dt$data))

    # render column group checkbox ui after loading the data
    checkboxGroupInput("columns", "Select columns to display", choices = cols, selected = cols)
  )

  #########################################
  # blocks with problem
  #########################################

  ######## dependent on columns selection ########
  observeEvent(input$columns, 
    dt$cols <- input$columns
    # update input$vars for pivottable tab
    updateSelectInput(session, "vars", "vars to use:", choices = dt$cols, selected = NULL)
  , ignoreNULL = FALSE)


  observeEvent(input$vars, 
    if( is.null(input$vars))  
      updateSelectInput(session, "fromvars", "select from vars:", choices = NULL, selected = NULL)  
    
    else 
      updateSelectInput(session, "fromvars", "select from vars:", choices = isolate(input$vars), selected = NULL)
    
  , ignoreNULL = FALSE)

  output$print <- renderPrint(
    list(
      paste("input$vars:",input$vars), 
      paste("input$columns:", input$columns),
      paste("input$fromvars:", input$fromvars)
    )
  )



shinyApp(ui = ui, server = server)

【参考方案1】：

基本上你很接近。唯一真正的问题是 updateSelectInput 似乎不喜欢其 NULL 参数中的 choices 值，因此您必须避免使用这些值。

我通过进行以下更改使代码正常工作：

在observerEvent(input$columns, 中添加了一条语句，该语句将dt$cols 设置为空字符串""，如果它具有值NULL 在observerEvent(input$vars, 中choices=NULL 更改为choices="" 调整了renderPrint 语句以制作更好的打印输出（使用双pastes，因此标签不会重复。

这是要验证的代码：

ui <- fluidPage(

  sidebarLayout(
    sidebarPanel( 

      fileInput("file", "Choose CSV File",
                # limit the file extention to the following:
                accept=c("text/csv", 
                         "text/comma-separated-values,text/plain", 
                         ".csv")),

      h5("Upload file for data analysis"),

      # no choices before a file uploaded
      uiOutput("columns"),

      # inputs to generate pivot table (demo in a single tab here, but in real app, this will be on a different tab)
      selectInput("vars", "vars to use:", choices = NULL, multiple = TRUE, selected = NULL),
      selectInput("fromvars", "select from vars:", choices = NULL, multiple = TRUE, selected = NULL)
    ),
    mainPanel( 
      verbatimTextOutput("print")
    ))
)

server <- function(input, output, session) 

  dt <- reactiveValues()

  # upload file
  observeEvent(input$file, 
    inFile <- input$file
    req(inFile)
    # upload the file to dataset
    dt$data = read.csv(inFile$datapath, header = TRUE)
  )

  # create columns groupcheckbox ui
  output$columns <- renderUI(

    # get the col names of f and assign them to a list
    cols = mapply(list, names(dt$data))

    # render column group checkbox ui after loading the data
    checkboxGroupInput("columns", "Select columns to display", choices = cols, selected = cols)
  )

  #########################################
  # blocks with problem
  #########################################

  ######## dependent on columns selection ########
  observeEvent(input$columns, 
    dt$cols <- input$columns
    if (is.null(dt$cols)) dt$cols <- ""
    # update input$vars for pivottable tab
    print("observerEvent")
    print(dt$cols)

    updateSelectInput(session, "vars", "vars to use:", choices = dt$cols, selected = NULL)
  , ignoreNULL = FALSE)


  observeEvent(input$vars, 
    if( is.null(input$vars))  
      updateSelectInput(session, "fromvars", "select from vars:", choices = "", selected = NULL)  
    
    else 
      updateSelectInput(session, "fromvars", "select from vars:", choices = input$vars, selected = NULL)
    
  , ignoreNULL = FALSE)

  output$print <- renderPrint(
    list(
      paste("input$columns:", paste(input$columns,collapse=",")),
      paste("input$vars:",paste(input$vars,collapse=",")), 
      paste("input$fromvars:", paste(input$fromvars,collapse=","))
    )
  )

shinyApp(ui = ui, server = server)

这就是它的样子：

【讨论】：

谢谢！这解决了！我想知道为什么 Shiny 包中没有记录这一点。

抱歉刚刚做了。谢谢！

谢谢。也检查您的旧答案。至少其中一个在我看来你应该接受。