在 R Shiny 中动态删除 UI 下拉元素

Question

可能是非常基本的问题 - 但无法将我发现的类似帖子翻译成我的确切问题。

在 R Shiny 应用程序中，我有一个由服务器上生成的向量填充的第一个下拉菜单 - 这使我可以做出一组选择。

我想要一个复选框，然后引入第二个下拉菜单 - 但如果我取消勾选复选框，我希望该下拉菜单消失。

我已经尝试过 - 请参阅下面的 MWE - 该图只是为了保持我的原始代码的结构（显然我知道我的下拉菜单什么都不做，但原始情况并非如此，但想要MWE 尽可能为“M”）。

如果我删除了 removeUI() 行，那么勾选复选框确实会根据需要创建一个新的下拉列表 - 但是取消勾选复选框无法将其删除。

我显然遗漏了一些东西；非常感谢任何帮助，因为我完全不喜欢 R Shiny，但真的想变得更好！

library(shiny)
library(shinyMobile)

# define UI elements
ui <- f7Page(

  f7SingleLayout(
    navbar = f7Navbar(
    ),
    f7Card(htmlOutput("initial_drop_down"), #first drop down
           f7checkBox(inputId = "switch", label = "Introduce second choice", FALSE), #tick box for second drop down if required
           htmlOutput("reactive_drop_down") #second drop down
    ),
    f7Shadow(
      intensity = 16,
      f7Card(
        plotOutput("distPlot", height = "800px") # plot - originally linked to drop down choices but an arbitrary graph here for simplicity
      )
    )  
  )


)

# server calculations
server <- function(input, output) {
  library(ggplot2)

  # generate first drop down - done on server side since usually choices vector is comprised of information read in from files
  output$initial_drop_down = renderUI({ 
    selectInput(inputId = "initial_choice",
                label = "First choice:",
                choices = c("Choice 1", "Choice 2", "Choice 3")) 
  })

  observeEvent(input$initial_choice, {

    # trying to add second drop down based on action in switch - not convinced my use of observeEvent is quite right - issue likely sits in here.
    observeEvent(input$switch, {

      if(input$switch == T){

        output$reactive_drop_down = renderUI({ 
          selectInput(inputId = "second_choice", 
                      label = "Second (dynamic) choice:", 
                      choices = c(1,2,3)) 
        })
      }else{
        removeUI(selector ="#reactive_drop_down")
      }
    })

    output$distPlot <- renderPlot({
      ggplot(data = cars) + geom_line(aes(x=speed, y=dist))
    })
  })
}

# Run the application 
shinyApp(ui = ui, server = server)

Answer 1

你能用conditionalPanel吗？将您的 htmlOutput 作为您的第二个输入放在您的 ui 中。我会避免使用嵌套的observeEvent 和output。

library(shiny)
library(shinyMobile)
library(ggplot2)

# define UI elements
ui <- f7Page(
  f7SingleLayout(
    navbar = f7Navbar(
    ),
    f7Card(htmlOutput("initial_drop_down"), #first drop down
           f7checkBox(inputId = "switch", label = "Introduce second choice", FALSE), #tick box for second drop down if required
           conditionalPanel(
             condition = "input.switch==1",
             htmlOutput("reactive_drop_down") #second drop down
           )
    ),
    f7Shadow(
      intensity = 16,
      f7Card(
        plotOutput("distPlot", height = "800px") # plot - originally linked to drop down choices but an arbitrary graph here for simplicity
      )
    )  
  )
)

# server calculations
server <- function(input, output) {

  # generate first drop down - done on server side since usually choices vector is comprised of information read in from files
  output$initial_drop_down = renderUI({ 
    selectInput(inputId = "initial_choice",
                label = "First choice:",
                choices = c("Choice 1", "Choice 2", "Choice 3")) 
  })

  output$reactive_drop_down = renderUI({ 
    selectInput(inputId = "second_choice", 
                label = "Second (dynamic) choice:", 
                choices = c(1,2,3)) 
  })

  output$distPlot <- renderPlot({
    ggplot(data = cars) + geom_line(aes(x=speed, y=dist))
  })

}

# Run the application 
shinyApp(ui = ui, server = server)