ui <- 
tagList(
	fluidPage(
		sidebarLayout(sidebarPanel(
			fileInput("upload", "Choose a file", accept = c('image/png', 'image/jpeg')),
			actionButton('click', 'Start')
		),
		mainPanel(
			imageOutput("output"),
			progressBar(id = "pb", value = 0, title = "", display_pct = TRUE)
		)
		)
	)
)

server <- 
function(input, output, session) {
	
	observeEvent(input$click, {
		img = magick::image_read(input$upload$datapath)
		fileName = sprintf("%s.jpg", gsub(":|-| ", "", Sys.time()))
		img %>% saveImage(fileName)

		output$output = renderImage({
			tmpfile = httr::GET(url = paste0("https://www.dropbox.com/sh/somelettersandnumbers?dl=0/", fileName), shinyhttr::progress(session, id = "pb"))
			list(src = tmpfile, contentType = "image/jpeg", style = paste0("width: 100%"))
		}, deleteFile=TRUE)
	})
}

shinyApp(ui = ui, server = server)

library(shiny)
library(shinyWidgets)
library(httr)
library(shinyhttr)

ui <- fluidPage(
  
  sidebarLayout(
    
    NULL,
    
    mainPanel(
      actionButton('download', 'Download 100MB file...'),
      tags$p("see R console to compare both progress bars."),
      progressBar(
        id = "pbar",
        value = 0,
        title = "",
        display_pct = TRUE
      )
    )
  )
)

server <- function(input, output, session) {
  observeEvent(input$download, {
    GET(
      url = "https://ftp.ncbi.nih.gov/1000genomes/ftp/1000G_2504_high_coverage/data/ERR3239276/NA06985.final.cram",
      shinyhttr::progress(session, id = "pbar")
    )
  })
}

shinyApp(ui, server)