在R Shiny应用程序中加载模式对话框后，如何设置对文本输入字段的关注？

如何解决在R Shiny应用程序中加载模式对话框后，如何设置对文本输入字段的关注？

我正在构建条形码扫描仪应用程序，以验证主条形码标签是否与从主条形码生成的所有辅助条形码标签匹配。当前迭代使用R，闪亮和模式对话框来扫描条形码标签。

我希望应用程序在弹出模式后自动聚焦在文本输入字段上，以便用户在扫描标签之前不必单击输入字段或标签。我已经读过JS focus函数可能合适，但是我不确定该函数需要在哪里实现。感谢您的帮助。

.libPaths(c(.libPaths(),temp <- tempdir()))
if(!require(shiny)) {install.packages("shiny",lib=temp,repos='http://cran.us.r-project.org')}
if(!require(shinyWidgets)) {install.packages("shinyWidgets",repos='http://cran.us.r-project.org')}
if(!require(shinyalert)) {install.packages("shinyalert",repos='http://cran.us.r-project.org')}
if(!require(devtools)) {install.packages("devtools",repos='http://cran.us.r-project.org')}
if(!require(shinyBarcode)) {devtools::install_github("CannaData/shinyBarcode")}
if(!require(shinyjs)) {install.packages("shinyjs",repos='http://cran.us.r-project.org')}
if(!require(V8)) {install.packages("V8",repos='http://cran.us.r-project.org')}

library(shiny)
library(shinyWidgets)
library(shinyalert)
library(shinyBarcode)
library(shinyjs)
library(V8)

options(shiny.sanitize.errors = TRUE)

options(rsconnect.max.bundle.size="xxxlarge")
  
ui <- fluidPage(
  
  # must include javascript dependencies
  useShinyalert(),# Set up shinyalert
  
  shinyBarcode::includeJsBarcode(cdn = TRUE),shinyBarcode::barcodeOutput("barcode"),useShinyjs(),extendShinyjs(script = "beep.js"),extendShinyjs(script = "beep2.js"),)

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

  vals <- reactiveValues(txt = NULL)
  
  # Create modals
  primary <- function(failed = FALSE) {
    modalDialog(
      textInput("txt","Scan primary tube"),footer = NULL,actionButton("reset","Reset")
    )
  }
  
  secondary <- function(failed = FALSE) {
    modalDialog(
      textInput("txt2","Scan secondary tube"),"Reset")
    )
  }
  
  # Show modal on startup
  showModal(primary())

  observeEvent(input$txt,{
    if (!is.null(input$txt) && nzchar(input$txt)) {
      vals$txt <- input$txt
      removeModal()
      showModal(secondary())
    } else {
      showModal(primary(failed = TRUE))
    }
  })
  
  observeEvent(input$txt2,{
    if (!is.null(input$txt2) & nzchar(input$txt2) & input$txt2!="Reset") {
      vals$txt2 <- input$txt2
      removeModal()
      if (vals$txt2==vals$txt) {
        js$beep()
        showModal(secondary())
      }
      else if (vals$txt2!=vals$txt) {
        js$beep2()
        shinyalert("Error","Primary and secondary labels do not match",type = "error")
        showModal(secondary())
      }
    } else if (!is.null(input$txt2) & nzchar(input$txt2) & input$txt2=="Reset"){
      showModal(primary())
    } else {
      showModal(secondary(failed = TRUE))
    }
  })
  
  observeEvent(input$reset,{
    showModal(primary())
    })
  
  output$barcode <- shinyBarcode::renderBarcode(vals$txt)

}

shinyApp(ui = ui,server = server)