R - 闪亮| ＆＃34;错误：类型＆＃39;关闭的对象＆＃39;不是子集表格＆＃34;使用downloadHandler

Question

我是Shiny的新手，我尝试从应用中的observeEvent（）实例生成下载按钮（对操作按钮作出反应），然后我得到＆＃34;错误：对象类型＆＃39;关闭＆＃39;不是子集表格＆＃34;在＆＃34;下载＆＃34;输出

我检查了类似问题的几个现有答案，以避免重复答案，但我无法在我的应用程序中找到错误，没有对象名称与内置函数冲突。也许它可能是由反应性条款引起的。

这是代码的结构，我尽可能地减少了它，使其变得通用，并将变量和对象名称翻译成英语以便更好地理解，因为它是西班牙语。非常感谢你的帮助。

library(shiny)

ui = fluidPage(


mainPanel(

    selectInput(inputId = "reportOption",
                label = "Select report",
                choices = c("A","B","C"),
                selected = "A",
                multiple = FALSE
    ),

    fileInput(inputId = "lastMonth",
              label = "Select last report",
              multiple = FALSE,
              accept = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
              buttonLabel = "Browse",
              placeholder = "..."
    ),

    fileInput(inputId = "currentMonth",
              label = "Select current file",
              multiple = FALSE,
              accept = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
              buttonLabel = "Browse",
              placeholder = "..."
    ),

    actionButton(inputId = "execute",
                 label = "Generate report"
    ),

    uiOutput("download")


)
)

server = function(input, output) {

  require("openxlsx")
  require("tibble") # Agregar columnas intermedias a un data frame

  observeEvent(input$execute,
               {fileLastMonth = input$lastMonth
               last.report = fileLastMonth$datapath

           fileCurrentMonth = input$currentMonth
           current.report = fileCurrentMonth$datapath

           # Nombre del nuevo reporte
           # recicle old file in order to preserve formatting attributes
           newFile = fileLastMonth$datapath

           # some code for calculations

           wb = loadWorkbook(newFile)

           # some code to write data in the workbook

           saveWorkbook(wb, file = newFile, overwrite = TRUE)

           output$download <- renderUI({
             downloadHandler(
               filename = function() {
                 paste(switch(input$reportOption,
                              "A"="A-File",
                              "B"="B-File",
                              "C"="C-File"),"xlsx",sep = ".")
               },
               content = function(file) {
                 file.copy(newFile, file)
               }


                )
               })
}

  )

}

shinyApp(ui = ui, server = server)