javascript - R leaflet - 显示/隐藏带有组层的 addControl() 元素

Question

我有一张传单 map ，它使用 HTML 自定义图例并使用 addControl 函数添加(以下:Leaflet Legend for Custom Markers in R)。

但是，我只希望在显示一组时显示图例，我尝试使用参数 group = "group name"，它不适用于 addControl功能。我也尝试过使用 layerId 参数但没有成功。

有什么想法吗？

可重现的例子:

library(leaflet)
# Sample Data
data(quakes)
quakes <- quakes[1:10,]

# Choose Icon:
leafIcons <- icons(
  iconUrl = ifelse(quakes$mag < 4.6,
               "http://leafletjs.com/docs/images/leaf-green.png",
               "http://leafletjs.com/docs/images/leaf-red.png"
 ),
  iconWidth = 38, iconHeight = 95,
  iconAnchorX = 22, iconAnchorY = 94)

html_legend <- "<img src='http://leafletjs.com/docs/images/leaf-
green.png'>green<br/>
<img src='http://leafletjs.com/docs/images/leaf-red.png'>red"

# Produce Map:
leaflet(data = quakes) %>% addTiles() %>%
  addMarkers(~long, ~lat, icon = leafIcons, group = "Group A") %>%
  addMarkers(~long, ~lat, icon = leafIcons, group = "Group B") %>%
  addControl(html = html_legend, position = "bottomleft") %>%
  addLayersControl(position = "topleft", overlayGroups = c("Group A","Group B"))

我希望 addControl html_legend 元素仅在组 A 可见时可见。

Answer 1

你是想用它制作一个 Shiny-App 吗？我为 Siny-App 写了一些类似的东西，其中只显示点击组的图例。

如果它不应该是一个 Shiny 的应用程序，你可以做这样的事情(你必须将传单 map 分配给一个变量(在本例中为“ map ”)。所以你可以调用它并在之后调整它。

map <- leaflet(data = quakes) %>% addTiles() %>%
  addMarkers(~long, ~lat, icon = leafIcons, group = "Group A") %>%
  addMarkers(~long, ~lat, icon = leafIcons, group = "Group B") %>%
  addControl(html = html_legend, position = "bottomleft") %>%
  addLayersControl(position = "topleft", overlayGroups = c("Group A","Group B"))

groups <- map$x$calls[[5]]$args[[2]]
activeGroup <- map$x$calls[[3]]$args[[5]]

if (any(activeGroup %in% "Group A")) {
  map %>% addLegend(title="Group A", position="bottomright", opacity=1, colors="red",
                           labels = "Group A")}

if (any(activeGroup %in% "Group B")) {
   map %>% addLegend(title="Group B", position="bottomright", opacity=1,colors="green",
                           labels = "Group B")} 

groups 变量存储所有当前的组，activeGroup 存储当前处于事件状态的组。然后，您可以将它与一些 if-else 语句一起使用，以仅显示事件组的图例。

尽管如此，它不会像普通 R 脚本那样具有交互性。您将不得不重复调用 activeGroup-call，以检查哪些组仍然处于事件状态。在 Shiny 中，将提供这种交互性。

这里是在 shiny-app 中的实现:

ui <- fluidPage(
  leafletOutput("map")
)
server <- function(input, output, session){
  output$map <- renderLeaflet({
    map <- leaflet(data = quakes) %>% addTiles() %>%
      addMarkers(~long, ~lat, icon = leafIcons, group = "Group A") %>%
      addMarkers(~long, ~lat, icon = leafIcons, group = "Group B") %>%
      addControl(html = html_legend, position = "bottomleft")
      addLayersControl(position = "topleft", overlayGroups = c("Group A","Group B"))
    map
  })

  observe({
    map <- leafletProxy("map") %>% clearControls()

    if (any(input$map_groups %in% "Group A")) {
      map <- map %>% addLegend(title="Group A", position="bottomright", opacity=1, colors="red",labels = "Group A")}
    if (any(input$map_groups %in% "Group B")) {
      map <- map %>% addLegend(title="Group B", position="bottomright", opacity=1,colors="green",labels = "Group B")}
  })
}

shinyApp(ui, server)