在R中使用leaflet并排插件

Question

我尝试使用Using arbitrary Leaflet JS plugins with Leaflet for R中的示例代码来实现leaflet并排插件。看起来很简单，到目前为止还没有成功。我不知道我做错了什么。非常感谢您的回复。谢谢,

library(leaflet)
library(htmltools)
library(htmlwidgets)


LeafletSideBySidePlugin <- htmlDependency("leaflet-side-by-side","2.0.0",
                                          src = c(href="https://github.com/digidem/leaflet-side-by-side"),
                                          script="leaflet-side-by-side.js")

# A function that takes a plugin htmlDependency object and adds
# it to the map. This ensures that however or whenever the map
# gets rendered, the plugin will be loaded into the browser.

registerPlugin <- function(map, plugin) {
   map$dependencies <- c(map$dependencies, list(plugin))
   map
}

leaflet() %>% addTiles() %>%
   setView(lng = 12, lat = 50, zoom = 4) %>%
   # Register leaflet-side-by-side plugin on this map instance
   registerPlugin(LeafletSideBySidePlugin) %>%
   onRender("
            function(el, x) {
var mylayer1 = L.tileLayer(
          'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',{
            maxZoom: 18
            })
var mylayer2 = L.tileLayer(
          '//stamen-tiles-{s}.a.ssl.fastly.net/watercolor/{z}/{x}/{y}.png',{
            maxZoom: 14
            })
            L.control.sideBySide(mylayer1, mylayer2).addTo(this);
            ")

Answer 1

只是偶然发现了这个问题。

我认为您错过了每个平铺地图层的addTo()方法。这是应该的。

leaflet() %>% addTiles() %>%
   setView(lng = 12, lat = 50, zoom = 4) %>%
   # Register leaflet-side-by-side plugin on this map instance
   registerPlugin(LeafletSideBySidePlugin) %>%
   onRender("
        function(el, x) {
          var mylayer1 = L.tileLayer(
            'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',{
             maxZoom: 18
             }).addTo(this);
          var mylayer2 = L.tileLayer(
             '//stamen-tiles-{s}.a.ssl.fastly.net/watercolor/{z}/{x}/{y}.png',{
             maxZoom: 14
             }).addTo(this);
        L.control.sideBySide(mylayer1, mylayer2).addTo(this);
        ")

Answer 2

我要赞扬Abuw的回答。如果有人想知道为什么它仍然不能工作，那是因为在onRender JavaScript中有一个不匹配的'{‘。

还要确保您的htmlDependency源代码确实存在。jsdelivr以应用程序/javascript格式通过npm和github提供了大多数可用的js库。使用它而不是原始的github路径，完整的工作代码应该如下所示：

library(leaflet)
library(htmltools)
library(htmlwidgets)


LeafletSideBySidePlugin <- htmlDependency("leaflet-side-by-side","2.0.0",
                                          src = c(href="https://cdn.jsdelivr.net/gh/digidem/leaflet-side-by-side@2.0.0/"),
                                          script="leaflet-side-by-side.js")

# A function that takes a plugin htmlDependency object and adds
# it to the map. This ensures that however or whenever the map
# gets rendered, the plugin will be loaded into the browser.

registerPlugin <- function(map, plugin) {
  map$dependencies <- c(map$dependencies, list(plugin))
  map
}

leaflet() %>% addTiles() %>%
  setView(lng = 12, lat = 50, zoom = 4) %>%
  # Register leaflet-side-by-side plugin on this map instance
  registerPlugin(LeafletSideBySidePlugin) %>%
  onRender("
        function(el, x) {
          var mylayer1 = L.tileLayer(
            'http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',{
             maxZoom: 18
             }).addTo(this);
          var mylayer2 = L.tileLayer(
          '//stamen-tiles-{s}.a.ssl.fastly.net/watercolor/{z}/{x}/{y}.png',{
             maxZoom: 14
             }).addTo(this);
        L.control.sideBySide(mylayer1, mylayer2).addTo(this);
        }")