Shinydashboard实现点击按钮后延迟30秒导入数据并展示

Got it, let's tackle your two needs step by step—hiding the table until data is ready, and adding a 30-second delay after clicking Submit without freezing the app. Here's the adjusted code with explanations:

Modified UI Code #

(Your original UI works just fine; we’ll handle visibility and behavior in the server logic)

library(shiny)
library(shinydashboard)
library(DT)
library(dataiku)

path <- dkuManagedFolderPath("receiver") # Folder with files to choose from

dashboardPage(
  dashboardHeader(title = "Catchy Title"),
  dashboardSidebar(
    selectizeInput("file", "Select File", list.files(path)),
    actionButton("submit", "Submit")
  ),
  dashboardBody(
    fluidRow(
      box(h2("Show Data"), 
          div(style = 'overflow-x: scroll', DT::dataTableOutput('mytable')), 
          width = 12)
    )
  )
)

Modified Server Code #

This is where the key changes happen to meet your requirements:

library(dataiku)
library(shiny)
library(shinydashboard)
library(DT)
library(dplyr)

shinyServer(function(input, output) {
  # Reactive value to store our final dataset (starts empty)
  final_dataset <- reactiveVal(NULL)
  
  # Trigger action when Submit button is clicked
  observeEvent(input$submit, {
    # Ensure a file is selected before proceeding
    req(input$file)
    
    # Clear any existing data so old results don't stay visible
    final_dataset(NULL)
    
    # Set up a one-time delayed execution (30 seconds = 30000 milliseconds)
    delayed_task <- observe({
      # Wait 30 seconds before running the dataset logic
      invalidateLater(30000)
      
      # Safely load and select the correct dataset
      tryCatch({
        intermediate_data <- dkuReadDataset("intermediate_dataset")
        # Check if intermediate dataset has rows to decide which final data to load
        df <- if (is.null(nrow(intermediate_data))) {
          dkuReadDataset("final_data1")
        } else {
          dkuReadDataset("final_data2")
        }
        # Update the reactive value with our loaded data
        final_dataset(df)
      }, error = function(e) {
        # Show a user-friendly error if something goes wrong
        showNotification(paste("Error loading data:", e$message), type = "error")
        final_dataset(NULL)
      })
      
      # Stop this observer after it runs once (no repeated tasks)
      cancelObserver(delayed_task)
    })
  })
  
  # Render the table ONLY when valid data is available
  output$mytable = DT::renderDataTable({
    req(final_dataset()) # This keeps the table hidden until data is ready
    final_dataset()
  })
})

Key Changes Explained: #

1. Reactive Data Storage:

   • We use reactiveVal(NULL) to hold our dataset. Initially, it’s empty, so the table won’t render (thanks to req(final_dataset()) in the table renderer).

2. Non-Blocking Delay:

   • Instead of Sys.sleep() (which freezes the entire app), we use invalidateLater(30000) inside a temporary observer. This tells Shiny to wait 30 seconds, then run the dataset-reading logic without locking up the UI.
   • cancelObserver() ensures this delayed task only runs once per Submit click.

3. Input & Data Validation:

   • req(input$file) makes sure the Submit action only triggers if a file is selected.
   • req(final_dataset()) guarantees the table stays hidden until valid data is loaded.

4. Error Handling:

   • Wrapping the dataset logic in tryCatch() prevents the app from crashing if there’s an issue loading files, and shows a clear error notification to the user.

内容的提问来源于stack exchange，提问作者Kasia Kulma