r - 如何在 Shiny 中保存传单 map

Question

继 this问题，我想将传单 map 保存和下载为 png 或 jpeg 图像。我有以下代码，但我不断收到错误消息。

ui <- fluidPage(
  leafletOutput("map"),
  downloadButton("dl")
)

server <- function(input, output, session) {
  output$map <- renderLeaflet({
    leaflet() %>% 
      addTiles()
  })

  output$dl <- downloadHandler(
    filename = "map.png",

    content = function(file) {
      mapshot(input[["map"]], file = file)
    }
  )
}

shinyApp(ui = ui, server = server)

我尝试下载(通过单击按钮)时遇到的错误是

Warning: Error in system.file: 'package' must be of length 1
Stack trace (innermost first):
    65: system.file
    64: readLines
    63: paste
    62: yaml.load
    61: yaml::yaml.load_file
    60: getDependency
    59: widget_dependencies
    58: htmltools::attachDependencies
    57: toHTML
    56: <Anonymous>
    55: do.call
    54: mapshot
    53: download$func [#11]
     4: <Anonymous>
     3: do.call
     2: print.shiny.appobj
     1: <Promise>
Error : 'package' must be of length 1

如果您能告诉我如何使用 leafletProxy 进行此操作，则可以加分。 .

Answer 1

可能这会有所帮助:

  server <- function(input, output, session) {

    map <- reactiveValues(dat = 0)

      output$map <- renderLeaflet({
        map$dat <- leaflet() %>% 
          addTiles()
      })

      output$dl <- downloadHandler(
        filename = "map.png",

        content = function(file) {
          mapshot(map$dat, file = file)
        }
      )
    }