r - 使用 R 为 Leaflet 中的图层控制框添加标题

Question

我希望沿着“可用图层”的行向图层控制框添加标题。

我的搜索使我只找到了一个相关结果:

Exact same question using JS. Unclear how to translate

我的代码:

map %>% leaflet() %>%
  addProviderTiles(provider = "CartoDB") %>%
  # Group 1 Polygons
  addPolygons(data = map[!is.na(map$var),] ,weight =1, 
              color = ~g1_pal(g1), fillOpacity = .6,
              group = "Group 1",
              # add labels
              label = ~labels,
              # highlight polygons on hover
              highlight = highlightOptions(weight = 5, color = "white",
                                           bringToFront = TRUE)) %>%
  # Group 2
  addPolygons(data = map[!is.na(map$var2),], weight =1, 
              color = ~g2_pal(g2), fillOpacity = .6,
              group = "Group 2",
              # add labels that display mean income
              label = ~labels2,
              # highlight polygons on hover
              highlight = highlightOptions(weight = 5, color = "white",
                                           bringToFront = TRUE)) %>%
  addLayersControl(baseGroups = c("Group 1", "Group 2"), 
                   options = layersControlOptions(collapsed=F, 
                                                  # Series of attempts 
                                                  label = "Layers",
                                                  title = "Layers"))

这些尝试都没有奏效。从上面的链接中确实可以访问到一个属性，但我不确定如何引用它。

Answer 1

最好的方法(我知道)是使用 htmlwidgets::onRender在渲染时将您的 Javascript 添加到 map 。这在 last section at the bottom of the last page in the docs 中有描述，所以很容易错过!
这是一个实现了 Saurabh Yadav 在他对 question you linked 的回答中描述的 Javascript 的示例。 .您只需将 Javascript 函数添加到 leaflet() 的末尾管道调用:

library(leaflet)

leaflet() %>%
    addTiles() %>%
    addLayersControl(
        overlayGroups = "MyImaginaryLine",
        options = layersControlOptions(collapsed = FALSE)) %>%
    htmlwidgets::onRender("
        function() {
            $('.leaflet-control-layers-overlays').prepend('<label style=\"text-align:center\">My Epic Title</label>');
        }
    ")