我目前正在使用 Android 版 Google map 实用程序库。我通过 API 调用接收给定区域的 geojson，并需要在 map 上显示该区域。
我通过调用
GeoJsonLayer layer = new GeoJsonLayer(getMap(), geoJsonData);
layer.addLayerToMap()
其中 getMap() 返回一个 GoogleMap 对象，geoJsonData 是一个 JSONObject。 此代码在与 geojson 关联的区域周围绘制边框。
下面的代码在该区域周围绘制了一个红色边框并用黄色填充。
GeoJsonLayer layer = new GeoJsonLayer(getMap(), geoJsonData);
GeoJsonPolygonStyle polygonStyle = layer.getDefaultPolygonStyle();
polygonStyle.setStrokeColor(ContextCompat.getColor(this, R.color.red));
polygonStyle.setFillColor(ContextCompat.getColor(this, R.color.yellow));
layer.addLayerToMap();
我在尝试设置整个 map 为黄色、区域边界为红色且区域填充颜色为正常颜色的 GeoJsonLayer 样式时遇到了麻烦。
有人能告诉我如何使用 GeoJson 数据在 Android 中实现这一点吗？ 一种选择是创建我自己的多边形形状。我可以使用覆盖整个 map 的坐标声明一个多边形，并使用从 geojson 返回的坐标添加一个洞。
但我认为必须有一些更简单的东西可以让我使用内置的 GeoJsonLayer 类，而不需要我自己解析 geojson。
最佳答案
您可以使用与您描述的相同的方法:
"declare a polygon using coordinates that cover the whole map, and i add a hole using the coordinates returned from the geojson"
GeoJSON 也支持 Polygon with "holes"，因此，对于具有“整个 map ”坐标的 GeoJSON
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-179.99,
89.99
],
[
-179.99,
0
],
[
-179.99,
-89.99
],
[
0,
-89.99
],
[
179.99,
-89.99
],
[
179.99,
0
],
[
179.99,
89.99
],
[
0,
89.99
],
[
-179.99,
89.99
]
],
[
[
-0.191208,
51.509869
],
[
-0.158464,
51.513287
],
[
-0.151769,
51.50554
],
[
-0.174471,
51.502178
],
[
-0.187989,
51.502444
],
[
-0.191208,
51.509869
]
]
],
"properties": {
"Territoire": 2
}
},
"properties": {
"name": "Hyde Park"
}
}
]
}
你会自动得到这样的东西:
如果您无法访问生成 GeoJSON 的后端，并且只收到目标区域的多边形，您可以添加“整个 map ”部分
[
[
-179.99,
89.99
],
[
-179.99,
0
],
[
-179.99,
-89.99
],
[
0,
-89.99
],
[
179.99,
-89.99
],
[
179.99,
0
],
[
179.99,
89.99
],
[
0,
89.99
],
[
-179.99,
89.99
]
]
通过如下代码进入多边形坐标数组的位置0(目标区域坐标之前):
JSONObject featureCollection = geoJsonData;
JSONArray features = featureCollection.getJSONArray("features");
for(int i = 0; i < features.length(); i++) {
JSONObject feature = features.getJSONObject(i);
JSONObject geometry = feature.getJSONObject("geometry");
String geometryType = geometry.getString("type");
if ("Polygon".equals(geometryType)) {
JSONArray coordinates = geometry.getJSONArray("coordinates");
if (coordinates.length() == 1) {
coordinates.put(coordinates.get(0));
JSONArray wholeMap = new JSONArray(
"[\n" +
" [\n" +
" -179.99,\n" +
" 89.99\n" +
" ],\n" +
" [\n" +
" -179.99,\n" +
" 0\n" +
" ],\n" +
" [\n" +
" -179.99,\n" +
" -89.99\n" +
" ],\n" +
" [\n" +
" 0,\n" +
" -89.99\n" +
" ],\n" +
" [\n" +
" 179.99,\n" +
" -89.99\n" +
" ],\n" +
" [\n" +
" 179.99,\n" +
" 0\n" +
" ],\n" +
" [\n" +
" 179.99,\n" +
" 89.99\n" +
" ],\n" +
" [\n" +
" 0,\n" +
" 89.99\n" +
" ],\n" +
" [\n" +
" -179.99,\n" +
" 89.99\n" +
" ]\n" +
" ]"
);
coordinates.put(0, wholeMap);
} else {
Log.d("OAA", "No need insert");
}
}
}
其中 geoJsonData - 没有“整个 map ”部分的 GeoJSON 数据，例如:
JSONObject geoJsonData = new JSONObject(
"{\n" +
" \"type\": \"FeatureCollection\",\n" +
" \"features\": [\n" +
" {\n" +
" \"type\": \"Feature\",\n" +
" \"geometry\": {\n" +
" \"type\": \"Polygon\",\n" +
" \"coordinates\": [\n" +
" [\n" +
" [\n" +
" -0.191208,\n" +
" 51.509869\n" +
" ],\n" +
" [\n" +
" -0.158464,\n" +
" 51.513287\n" +
" ],\n" +
" [\n" +
" -0.151769,\n" +
" 51.50554\n" +
" ],\n" +
" [\n" +
" -0.174471,\n" +
" 51.502178\n" +
" ],\n" +
" [\n" +
" -0.187989,\n" +
" 51.502444\n" +
" ]\n" +
" ]\n" +
" ],\n" +
" \"properties\": {\n" +
" \"Territoire\": 2\n" +
" }\n" +
" },\n" +
" \"properties\": {\n" +
" \"name\": \"Hyde Park\"\n" +
" }\n" +
" }\n" +
" ]\n" +
"}"
);
更新 GeoJSON 还支持具有多个“孔”的多边形，GeoJSON 为海德和摄政公园显示了 2 个“孔”:
{
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-179.99,
89.99
],
[
-179.99,
0
],
[
-179.99,
-89.99
],
[
0,
-89.99
],
[
179.99,
-89.99
],
[
179.99,
0
],
[
179.99,
89.99
],
[
0,
89.99
],
[
-179.99,
89.99
]
],
[
[
-0.191208,
51.509869
],
[
-0.158464,
51.513287
],
[
-0.151769,
51.50554
],
[
-0.174471,
51.502178
],
[
-0.187989,
51.502444
],
[
-0.191208,
51.509869
]
],
[
[
-0.167685,
51.530226
],
[
-0.163737,
51.534924
],
[
-0.151849,
51.537566
],
[
-0.151849,
51.537566
],
[
-0.146914,
51.535964
],
[
-0.145625,
51.525325
],
[
-0.155538,
51.523589
],
[
-0.167685,
51.530226
]
]
],
"properties": {
"Territoire": 2
}
},
"properties": {
"name": "Hyde Park"
}
}
]
}
关于Android Google Maps GeoJson，如何为整个 map 着色一种颜色，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49825918/