使用 R 向 Leaflet 中的图层控制框添加标题

Question

我希望按照“可用图层”的行向图层控制框添加标题。

我的搜索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看到有一个可以访问的属性，但我不确定如何引用它。

Answer 1

最好的方法（据我所知）是使用htmlwidgets::onRender 在渲染时将您的Javascript 添加到地图中。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 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() 管道调用的末尾即可：

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>');
        }
    ")