Your code could use a lot of work and I suggest you take a look at reactiveValues and eventReactive and not using functions in your server file for example - I actually started rewriting your entire app but then decided to focus on the question at hand.
Here is a start:
library(shinydashboard)library(leaflet)library(ggplot2)library(DT)library(openxlsx)# -----------------------------------------------------------------------------# Dashboard UI# -----------------------------------------------------------------------------dataset <- c("P1-Long-Term-Unemployment-Statistics","P1-OfficeSupplies","P1-SuperStoreUS-2015")ui <- dashboardPage( dashboardHeader( title = "Validation Tool" ), dashboardSidebar( sidebarMenu( menuItem("Upload File", tabName = "file", icon = icon("database")), menuItem("View Tables", tabName = "view", icon = icon("database")), menuItem("Append Data", tabName = "append", icon = icon("database")), menuItem("Update Table", tabName = "update", icon = icon("crosshairs")), menuItem("Construct Table", tabName = "construct", icon = icon("fire")) ), div(style = "padding-left: 15px;padding-right: 5px; padding-top: 40px;", p(class = "small", "Note : This validation tools automates the mainstream process involved in creating a Master data for detailed analysis ") ) ), dashboardBody( tabItems( # Current location ------------------------------------------------------ tabItem(tabName = "view", mainPanel( titlePanel(h2("Explore Datasets")),fluidRow( column(6, uiOutput("tables") ), column(6, uiOutput("sheets") ) ), tabsetPanel(type="tab", tabPanel("Data",br(),div(DT::dataTableOutput("table"),style = "font-size: 100%;width: 150%") ), tabPanel("Summary"), tabPanel("Plot") ) ) ), ##################### Tab Item 2 Begins ########################### tabItem(tabName = "file", mainPanel( titlePanel(h2("Upload your XLSX file here ")), fluidRow( column(6, fileInput('file1', 'Choose a XLSX file to upload', accept = c('.xlsx'))), column(6,actionButton("save","Save to Database")), div(DT::dataTableOutput("contents"),style = "font-size: 100%;width: 150%") ) ) ) #####################End of Tab Item 2############################# ) ))# -----------------------------------------------------------------------------# Dashboard server code# -----------------------------------------------------------------------------options(shiny.maxRequestSize = 30*1024^2)validate_file <- function(input) { if (length(input) > 0 & !is.null(input) & input!= "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet") {"Please upload a XLSX file" } else { NULL }}server <- function(input, output,session) { my_file <- function(){ my_file <- paste0("D:/Dataset/",input$table,".xlsx") } sheetNames <- function(){ sheetNames <- getSheetNames(my_file()) } output$sheets <- renderUI({ selectInput("sheet","Sheet:",choices = sheetNames()) }) tablelist<-c() output$tables <- renderUI({ selectInput("table","Table:",choices = files()) }) output$table <- renderDT(read.xlsx(my_file(),sheet=as.character(input$sheet)),class="display nowrap compact", filter = "top",options = list( scrollX = T, scrollCollapse=TRUE, pageLength=20,scrollY="260px",lengthMenu=c(20,40,60,80,100), search = list(regex = FALSE, caseInsensitive = FALSE))) # output$contents <- renderTable({ # # input$file1 will be NULL initially. After the user selects # # and uploads a file, it will be a data frame with 'name', # # 'size', 'type', and 'datapath' columns. The 'datapath' # # column will contain the local filenames where the data can # # be found. # # inFile <- input$file1 # if (is.null(inFile)) # return(NULL) # read.xlsx(inFile$name, sheet=1) # }) ############################## Validate Scenario ######################## v <- reactive({ type <- input$file1 validate(validate_file(type$type)) }) ############################# Scenario Ends ############################ output$contents <- renderDT({ # input$file1 will be NULL initially. After the user selects # and uploads a file, it will be a data frame with 'name', # 'size', 'type', and 'datapath' columns. The 'datapath' # column will contain the local filenames where the data can # be found. inFile <- req(input$file1) v() if (is.null(inFile)) return(NULL) read.xlsx(inFile$datapath, sheet=1) },class="display nowrap compact", options = list( scrollX = T, pageLength=20,scrollY="340px",lengthMenu=c(20,40,60,80,100) )) ############################# ACtion Button Save ###################################### files <- eventReactive(input$save,{ filenm <- input$file1 filenm$name tablelist <- c(tablelist,as.character(filenm$name)) filePath <- c(filePath,as.character(filenm$dataPath)) return (tablelist) }) ############################# End of Action button ####################################}shinyApp(ui, server)I moved inFile <- req(input$file1) before v() and added the req() to remove the initial error message on loading the app but the main work was in this piece:
files <- eventReactive(input$save,{ filenm <- input$file1 filenm$name tablelist <- c(tablelist,as.character(filenm$name)) filePath <- c(filePath,as.character(filenm$dataPath)) return (tablelist) })and then changing files to files() here:
output$tables <- renderUI({ selectInput("table","Table:",choices = files()) })This should answer your current question but there are lots of other issues with your app so let me know when they come up.