如何在Shiny中的ObserveEvent中使用"withProgress“进行所有计算？

library(shiny)

ui <- fluidPage(
  actionButton("startBtn", "Start Calculation"),
  verbatimTextOutput("output")
)

server <- function(input, output) {
  observeEvent(input$startBtn, {
    withProgress(message = 'Calculating...', value = 0, {
      # Step 1
      setProgress(0.2, detail = "Step 1")
      # Perform calculation for step 1

      # Step 2
      setProgress(0.5, detail = "Step 2")
      # Perform calculation for step 2

      # Step 3
      setProgress(0.8, detail = "Step 3")
      # Perform calculation for step 3

      # Step 4
      setProgress(1, detail = "Step 4")
      # Perform calculation for step 4
    })
  })

  output$output <- renderPrint({
    "Calculation completed!"
  })
}

shinyApp(ui, server)