问题
I am having a real pain of trying to draw multiple polygons from a geojson file. Below I have pasted a sample of the geojson file and the javascript used to access it. It seems the main problem I am running into is that I cannot get into that array of coordinates nested in each record as it either returns the error that "coordinates" is undefined or that there is no method "setMap" for undefined. I have been able to return other nested aspects of a similar JSON file (this is a test file, the real one actually has data, just trying to get the polygon drawing here), but getting those coordinates is not working. I am not a javascript master so I can't tell where the code is failing to make the proper access.
thanks in advance.
the json data looks like this:
var data={
"type": "FeatureCollection",
"features": [
{
"type": "Feature",
"id": 1,
"properties": {
"Name": "",
"description": "",
"timestamp": "",
"begin": "",
"end": "",
"altitudeMode": "clampToGround",
"tessellate": 1,
"extrude": -1,
"visibility": -1
},
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-83.126571,
42.348706
],
[
-83.126520,
42.348634
],
[
-83.126516,
42.348635
],
[
-83.126147,
42.348778
],
[
-83.126144,
42.348780
],
[
-83.126195,
42.348852
],
[
-83.126199,
42.348851
],
[
-83.126568,
42.348708
],
[
-83.126571,
42.348706
]
]
]
}
},
{
"type": "Feature",
"id": 2,
"properties": {
"Name": "",
"description": "",
"timestamp": "",
"begin": "",
"end": "",
"altitudeMode": "clampToGround",
"tessellate": 1,
"extrude": -1,
"visibility": -1
},
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-83.132805,
42.356496
],
[
-83.132753,
42.356423
],
[
-83.132751,
42.356424
],
[
-83.132243,
42.356624
],
[
-83.132241,
42.356625
],
[
-83.132294,
42.356698
],
[
-83.132296,
42.356697
],
[
-83.132802,
42.356497
],
[
-83.132805,
42.356496
]
]
]
}
},
{
"type": "Feature",
"id": 3,
"properties": {
"Name": "",
"description": "",
"timestamp": "",
"begin": "",
"end": "",
"altitudeMode": "clampToGround",
"tessellate": 1,
"extrude": -1,
"visibility": -1
},
"geometry": {
"type": "Polygon",
"coordinates": [
[
[
-83.126776,
42.351813
],
[
-83.126492,
42.351413
],
[
-83.126189,
42.351525
],
[
-83.126191,
42.351528
],
[
-83.126376,
42.351807
],
[
-83.126776,
42.351813
]
]
]
}
}
etc...
]
}
I've got the javascript as below, using the example used at geojason.info: http://demos.geojason.info/complex-geojson-polygons-google-maps-demo.php
var points;
var pointsMore;
var polygon;
var map;
function initializeMap() {
map = new google.maps.Map(document.getElementById("map_canvas"), {
zoom: 11,
center: new google.maps.LatLng(42.347727, -83.058014),
mapTypeId: google.maps.MapTypeId.TERRAIN
});
var polygon = createPolygons(pointsMore);
//this is where the problem is...check nesting.
polygon.setMap(map);
}
function createPolygons(pointsMore) {
for (var y = 0; y < data.features.length; y++) {
var points = data.features[y];
for (var z = 0; points.geometry.length; z++) {
var pointsMore = points.geometry[z];
var coords = pointsMore.coordinates;
var paths = [];
$.each(coords,function(i,n){
$.each(n, function(j,o){
var path = [];
$.each(o,function(k,p){
var ll = new google.maps.LatLng(p[1],[0]);
path.push(ll);
});
paths.push(path);
});
});
var polygon = new google.maps.Polygon({
paths: paths,
strokeColor: "#FF7800",
strokeOpacity: 1,
strokeWeight: 2,
fillColor: "#46461F",
fillOpacity: 0.25
});
return polygon;
}
}
}
回答1:
points.geometry is an object, but you're trying to loop through it like an array. To access the coordinates, use:
var coordinates = data.features[y].geometry.coordinates;
回答2:
I'm prefering to integrate the geojson data => map.data.addGeoJson(data); where data is simply your js var containing the features details. here's an example of initialize() function :
function initialize() {
// Create a simple map.
map = new google.maps.Map(document.getElementById('map_canvas'), {
zoom: 11,
center: {
lat: 42.347727,
lng: -83.058014
},
mapTypeId: google.maps.MapTypeId.TERRAIN
});
// Load a GeoJSON from the same server as our demo.
map.data.addGeoJson(mapdata);
setStyle();
};
回答3:
Here is the code to get coordinate
var coordinates = data.features[0].geometry.coordinates;
There maybe more than one arrays
var first = data.features[0].geometry.coordinates[0];
var second= data.features[0].geometry.coordinates[1];
来源：https://stackoverflow.com/questions/7389811/accessing-coordinates-in-a-nested-geojson-file-to-draw-polygons-with-google-maps