R闪亮- uiOutput没有在menuItem中呈现

Question

问题

为什么在server上生成并在带有uiOutput()的ui上呈现的server没有在menuItem()中显示

示例

在这个简单的应用程序中，我在server上生成一个server(注意，menuItem是故意注释掉的)，它的工作原理与预期一样。

library(shiny)
library(shinydashboard)

rm(ui, server)

ui <- dashboardPage(
    dashboardHeader(),

    dashboardSidebar(
        sidebarMenu(
            #menuItem(text = "data options",
                      checkboxGroupInput(inputId = "cbg_group1", label = "group 1", 
                                         choices = c("some","check","boxes","to","choose","from") ),
                       uiOutput("sli_val1"),
                       checkboxGroupInput(inputId = "cbg_group2", label = "group 2", 
                                          choices = c("another","set","of","check","boxes") ),
            #                ),
            menuItem(text = "another tab")
            )
    ),
    dashboardBody()
)

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

    withProgress(message = "loading page", value=0.1, {
        ## simulate loading some data
        Sys.sleep(3)

        ## slider input
        output$sli_val1 <- renderUI({
            sliderInput(inputId = "sli_val1", 
                        label = "values", min = 0, max = 100,
                        value = c(25, 75) )
        })
        setProgress(value=1, detail="Complete")
    })
}

shinyApp(ui = ui, server = server)

但是，当我将uiOutput移动到menuItem( )中时，输出将不再呈现：

ui <- dashboardPage(
    dashboardHeader(),

    dashboardSidebar(
        sidebarMenu(
            menuItem(text = "data options",
                     checkboxGroupInput(inputId = "cbg_group1", label = "group 1", 
                                        choices = c("some","check","boxes","to","choose","from") ),
                     uiOutput("sli_val1"),
                     checkboxGroupInput(inputId = "cbg_group2", label = "group 2", 
                                        choices = c("another","set","of","check","boxes") )
                             ),
            menuItem(text = "another tab")
            )
    ),
    dashboardBody()
)

Answer 1

首先，我会将uiOutput("sli_val1")转换为uiOutput("out_sli_val1")，以防止重复的Ids。

关于您的问题:当闪亮在文档中运行并呈现/绑定所有可能的输出时，这是一件很奇怪的事情。默认操作是忽略所有隐藏的输出元素--这意味着不完全忽略(输出"sli_val1“是正常的)，但是它们的函数被挂起，不允许呈现任何子元素。

所以问题是，在启动时，这个输出隐藏在子项树中，然后被忽略。

修复可以通过调用取消这种约束行为来完成。

outputOptions(output, "out_sli_val1", suspendWhenHidden = FALSE)

但如何和在哪里？在运行“数据加载”之前，必须设置此选项。但是如果output$out_sli_val1没有任何分配给它的东西(is NULL)，它会抛出错误。为了避免这种情况，我们可以初始化一个空的UI块，它在“数据加载”中被覆盖。

下面是您使用2行额外代码(以及修改后的输出Id)进行的最小修正：

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(
    sidebarMenu(
      menuItem(text = "data options", 
        checkboxGroupInput(inputId = "cbg_group1", label = "group 1", 
                           choices = c("some","check","boxes","to","choose","from") ),
        uiOutput("out_sli_val1"),
        checkboxGroupInput(inputId = "cbg_group2", label = "group 2", 
                           choices = c("another","set","of","check","boxes") )
      ),
      menuItem(text = "another tab")
    )
  ),
  dashboardBody()
)

server <- function(input, output, session){
  output$out_sli_val1 <- renderUI({})
  outputOptions(output, "out_sli_val1", suspendWhenHidden = FALSE)

  withProgress(message = "loading page", value=0.1, {
    ## simulate loading some data
    Sys.sleep(3)

    ## slider input
    output$out_sli_val1 <- renderUI({
      sliderInput(inputId = "sli_val1", label = "values", min = 0, max = 100, value = c(25, 75) )
    })

    setProgress(value=1, detail="Complete")
  })
}

shinyApp(ui = ui, server = server)