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我是新来的，想要帮助弄清楚如何在 R 的 Leaflet 地图中使用 Google Maps API 调用 Google Maps 基础层。这是我到目前为止所学到的：

  1. Pavel Shramov 的 Leaflet 插件允许从 Leaflet JS 内部调用 Google 的基本地图，据我所知，这种方式符合 Google 的 ToS。这里有一个例子，效果很好。
  2. 有关通过 htmltools 和 htmlwidgets在 Leaflet for R 中使用任意 Leaflet JS 插件的一般说明。

基于以上内容，我了解我在 R 中的代码需要如下所示，但我无法加载 Google 底图：

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

# 1: Tell htmlwidgets where to look for the script and stylesheets
gLeafletPlugin <- htmlDependency("gLeaflet","1.9.0",
                           src = c(href = "https://cdnjs.cloudflare.com/ajax/libs/leaflet-plugins/1.9.0/layer/tile/"),
                           script = "Google.js")

# FIRST PLACE WHERE I AM STUCK: I am pretty sure, I also need to pass on 
# the Google Maps API script reference before or along with the above command,
# but trying to include two htmlDependency objects together in a list, did not
# work. Maybe I wasn't doing it right.


# 2: Make a map and add the htmlDependency object to it
registerPlugin <- function(map, plugin) {
    map$dependencies <- c(map$dependencies, list(plugin))
    map
    }

leaflet() %>% 
  setView(76.65, 12.32, zoom = 9) %>%
    registerPlugin(gLeafletPlugin) %>%
      # 3: Pass on custom JS logic: SECOND PLACE WHERE I AM STUCK
      onRender("function(el, x) {
         L.Google('TERRAIN').addTo(this);
        }")

如果有人能告诉我：（a）当涉及多个脚本时，注册 htmlDependency 的正确方法将不胜感激；(b) 调用显示 Google 地形底图所需的额外 JS 逻辑的正确语法。

谢谢！

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