R 当添加css“style=position:fixed；”时，侧边栏面板收缩

我需要一个固定的侧边栏面板，但是当addstyle='position:fixed；'时，我遇到了问题。添加样式时，侧边栏面板会收缩。 样式为'position:fixed；'的代码在下面此图显示了不带和带有样式='position:fixed；'我怎样才能使sibarPanel不收缩

# User interface
ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(width = 2, 
                 style='position: fixed;',
                 uiOutput("countryList")),
    mainPanel(
      plotOutput("distPlot1"),
      plotOutput("distPlot2"),
      plotOutput("distPlot3"))))
# Server logic  
server <- function(input, output) {
  output$countryList <- renderUI({
    selectizeInput("countryName", "Country",
                   choices = c('Austria', 'The United Kingdom'))})
  output$distPlot1 <- renderPlot({hist(rnorm(100))})
  output$distPlot2 <- renderPlot({hist(rnorm(200))})
  output$distPlot3 <- renderPlot({hist(rnorm(300))})}

shinyApp(ui, server)

---

我认为这是一种方式：

library(shiny)
# User interface
ui <- fluidPage(
  div(class = "row",
      div(class = "col-sm-4", 
          tags$form(class = "well col-sm-4", `data-spy` = "affix", # this is the sidebar
              uiOutput("countryList")
          )
      ), 
      div(class = "col-sm-8", # this is the main panel
          plotOutput("distPlot1"),
          plotOutput("distPlot2"),
          plotOutput("distPlot3")
      )
  )
)

# Server logic  
server <- function(input, output) {
  output$countryList <- renderUI({
    selectizeInput("countryName", "Country",
                   choices = c('Austria', 'The United Kingdom'))})
  output$distPlot1 <- renderPlot({hist(rnorm(100))})
  output$distPlot2 <- renderPlot({hist(rnorm(200))})
  output$distPlot3 <- renderPlot({hist(rnorm(300))})}

shinyApp(ui, server)