Question

每天，我需要在地图上绘制路径，并添加4、5或8分钟之类的文字。指示从起点到目的地乘车要花费多长时间（请参见下图）。我认为使用R中的Leaflet创建Shiny应用程序会有所帮助（代码如下所示）。

我利用leaflet.extras包中的addDrawToolbar绘制路径，如所附地图所示。但是我不知道，也找不到如何以与绘制路径相同的方式添加文本。解决方案并不一定要使用R。我的目标是为想要做这些事情而又不知道如何编码的人创建一个应用。

library(shiny)
library(leaflet)
library(leaflet.extras)


ui = fluidPage(
      tags$style(type = "text/css", "#map {height: calc(100vh - 20px) 
      !important;}"),
      leafletOutput("map")
      )

server = function(input,output,session){
             output$map = renderLeaflet(
                 leaflet()%>%

         addTiles(urlTemplate = "http://mt0.google.com/vt/lyrs=m&hl=en&x= 
              {x}&y={y}&z={z}&s=Ga")%>%

         addMeasure(
              primaryLengthUnit = "kilometers",
              secondaryAreaUnit = FALSE
         )%>%

         addDrawToolbar(
              targetGroup='draw',

              editOptions = editToolbarOptions(selectedPathOptions = 
                    selectedPathOptions()),

              polylineOptions = filterNULL(list(shapeOptions = 
                    drawShapeOptions(lineJoin = "round", weight = 8))),

              circleOptions = filterNULL(list(shapeOptions = 
                    drawShapeOptions(),
                    repeatMode = F,
                    showRadius = T,
                    metric = T,
                    feet = F,
                    nautic = F))) %>%
        setView(lat = 45, lng = 9, zoom = 3) %>%
        addStyleEditor(position = "bottomleft", 
                 openOnLeafletDraw = TRUE)
 )
}

 shinyApp(ui,server)

Answer 1

执行此操作的一种方法是，在双击传单地图时提示用户添加文本。双击坐标可处理放置文本的位置，弹出提示可处理文本应说的内容。

library(shiny)
library(leaflet)
library(leaflet.extras)

server = function(input,output,session){

  # Create reactive boolean value that indicates a double-click on the leaflet widget
  react_list <- reactiveValues(doubleClick = FALSE, lastClick = NA)
  observeEvent(input$map_click$.nonce, {
    react_list$doubleClick <- identical(react_list$lastClick, input$map_click[1:2])
    react_list$lastClick   <- input$map_click[1:2]
  })

  # Upon double-click, create pop-up prompt allowing user to enter text
  observeEvent(input$map_click[1:2], {
    if (react_list$doubleClick) {
      shinyWidgets::inputSweetAlert(session, "addText", title = "Add text:")
    }
  })

  # Upon entering the text, place the text on leaflet widget at the location of the double-click
  observeEvent(input$addText, {
    leafletProxy("map") %>% 
      addLabelOnlyMarkers(
        input$map_click$lng, input$map_click$lat, label = input$addText, 
        labelOptions = labelOptions(noHide = TRUE, direction = "right", textOnly = TRUE,
                                    textsize = "15px"))
  })

  # Clear out all text if user clears all layers via the toolbar
  observeEvent(input$map_draw_deletestop, {
    if ( length(input$map_draw_all_features$features) < 1 ) {
      leafletProxy("map") %>% clearMarkers()
    }
  })

  output$map <- renderLeaflet({
    leaflet(options = leafletOptions(doubleClickZoom = FALSE)) %>%
      addProviderTiles(providers$CartoDB.Positron) %>% 
      addMeasure(
        primaryLengthUnit = "kilometers",
        secondaryAreaUnit = FALSE) %>%
      addDrawToolbar(
        targetGroup     ='draw',
        editOptions     = editToolbarOptions(selectedPathOptions = selectedPathOptions()),
        polylineOptions = filterNULL(list(shapeOptions = drawShapeOptions(lineJoin = "round", weight = 8))),
        circleOptions   = filterNULL(list(shapeOptions = drawShapeOptions(), repeatMode = F, showRadius = T,
                                          metric = T, feet = F, nautic = F))) %>%
      setView(lng = -73.97721, lat = 40.7640, zoom = 15)
  })
}

shinyApp(ui = fluidPage( leafletOutput("map") ) , server)

如何在传单地图上添加文本？

1 个答案: