更改R Shiny中的选项卡后，updatePickerInput不更新值

Question

我有一个下拉菜单，其值应在我更改标签时更新。但是到目前为止，当我更改选项卡时，我仍然必须去下拉菜单中选择先前的值以获得新的值列表。如何解决这些问题，即一旦切换选项卡，下拉值也将被更新。下面是我的代码。

library(shiny)
library(shinyWidgets)
library(shinydashboard)

sidebar <- dashboardSidebar(
  sidebarMenu(id = "tab",
              menuItem("1", tabName = "1"),
              menuItem("2", tabName = "2"),
              menuItem("3", tabName = "3"),
              menuItem("4", tabName = "4")

  )
)
body <-   ## Body content
  dashboardBody(box(width = 12,fluidRow(
    column(
      width = 3,
      pickerInput(
        inputId = "metric",
        label = h4("Metric Name"),
        choices = c(
          "alpha",
          "beta"
        ),

        width = "100%"
      )
    )
  )))

ui <-   dashboardPage(dashboardHeader(title = "Scorecard"),
                      sidebar,
                      body)

# Define the server code
server <- function(input, output,session) {
  observeEvent(input$metric, {
    if (input$tab == "1"){
      choices <- c(
        "alpha",
        "beta"
      )
    }
    else if (input$tab == "2") {
      choices <- c(
        "apple",
        "orange"
      )
    }
    else {
      choices <- c(
        "foo",
        "zoo",
        "boo"
      )
    }
    updatePickerInput(session,
                      inputId = "metric",
                      choices = choices)
  })

}

shinyApp(ui = ui, server = server)