r - 将输入值存储在 Shiny 的小部件中？

Question

我试图理解存储在shiny inputwidgets中的值。我编写了下面的代码，该代码输出 sliderInput 并根据 sliderInput 的值生成另一个 o/p 元素，即

如果sliderInput值> 30，那么它会生成groupedradiobutton 否则它会生成一个文件上传按钮

library(shiny)
library(shinyWidgets)
ui <- fluidPage(
  sliderInput(inputId = "num", 
              label = "Choose a number", 
              value = 25, min = 1, max = 100),
  uiOutput("uploadorSelect"),
  textOutput("RadioButtonValue")
)

server <- function(input, output) {
  output$uploadorSelect <- renderUI({
    x<-input$num

    if( x > 30 ){
      # render grouped radio buttons  
      radioGroupButtons(inputId = "opbAppendRemoveMonthlyOption",choices =c("Append","Continue"), status = "success",
                        direction = "horizontal",justified = F,checkIcon = list(yes=icon("ok",lib="glyphicon")),selected = character(0))

    }else{
      # render upload button
      fileInput(inputId="btnUploadMonthlyFile",label = "Upload Monthly Data file") 
    }
  })

  output$RadioButtonValue<-renderText({
    x<-(input$opbAppendRemoveMonthlyOption)
    return(x)

  })
}

shinyApp(ui = ui, server = server)

情况:-

第 1 步 - 我将 sliderInput 的值更改为 31，这会生成 groupedradiobutton，然后从单选按钮中选择 Append

第 2 步 - 我再次将 sliderInput 的值更改为 32，这会重新生成 groupedradiobutton，我相信这应该重置 output$RadioButtonValue 中使用的 input$opbAppendRemoveMonthlyOption 的值 block 为 Null，但它仍然保留在步骤 1 中选择的值

我认为这是因为当我在 output$RadioButtonValue 中引用 input$opbAppendRemoveMonthlyOption 时，它返回缓存的值？如果是这样，每次更改 sliderInput 的值时如何将值设置为默认值？

Answer 1

您的应用设置正确，但问题似乎在于 opbAppendRemoveMonthlyOption 的新值“未选择任何内容”的消息丢失。例如，如果您将默认的selected选项更改为“继续”，那么每次更改 slider 时它都会正确重置。

通常，您还可以在响应式(Reactive)表达式中使用相应的更新函数来更改输入的值，如下所示:

  observeEvent({input$num}, {
    updateRadioGroupButtons(session, "opbAppendRemoveMonthlyOption",
                            selected = character(0))
  })

但是，正如在创建输入时一样，当尝试将值设置回未选定状态时，此消息将被忽略，但如果将其设置为选项之一，则该消息有效。请注意，Shiny 文档 (?radioButtons) 中不鼓励使用未选中状态，因此可能不完全支持它。

If you need to represent a "None selected" state, it's possible to default the radio buttons to have no options selected by using selected = character(0). However, this is not recommended, as it gives the user no way to return to that state once they've made a selection. Instead, consider having the first of your choices be c("None selected" = "").

您可以使用一些 JavaScript 来解决此问题，以在单击 slider 时强制重置input 值。

library(shiny)
library(shinyWidgets)
ui <- fluidPage(
  tags$div(
    sliderInput(inputId = "num", 
                label = "Choose a number", 
                value = 25, min = 1, max = 100),
    onchange = "Shiny.onInputChange('opbAppendRemoveMonthlyOption', '')"
  ),
  uiOutput("uploadorSelect"),
  textOutput("RadioButtonValue")
)

server <- function(input, output) {
  output$uploadorSelect <- renderUI({
    x<-input$num

    if( x > 30 ){
      # render grouped radio buttons  
      radioGroupButtons(inputId = "opbAppendRemoveMonthlyOption",choices =c("Append","Continue"), status = "success",
                        direction = "horizontal",justified = F,checkIcon = list(yes=icon("ok",lib="glyphicon")),selected = character(0))

    }else{
      # render upload button
      fileInput(inputId="btnUploadMonthlyFile",label = "Upload Monthly Data file") 
    }
  })

  output$RadioButtonValue<-renderText({
    x<-(input$opbAppendRemoveMonthlyOption)
    return(x)

  })
}

shinyApp(ui = ui, server = server)

More info Shiny<->JavaScript messaging from RStudio.com