Drawing Multiple Polygons on Google Maps API v3 from MySQL database

Question

So, I am attempting to draw multiple polygons onto a google map via polygon spatial data from my MySQL table. I have a php script that outputs the following XML based off my table data.

<subdivision name="Auburn Hills">
    <coord lat="39.00748" lng="-92.323222"/>
    <coord lat="39.000843" lng="-92.323523"/>
    <coord lat="39.000509" lng="-92.311592"/>
    <coord lat="39.007513" lng="-92.311378"/>
    <coord lat="39.00748" lng="-92.323222"/>
</subdivision>
<subdivision name="Vanderveen">
    <coord lat="38.994206" lng="-92.350645"/>
    <coord lat="38.985033" lng="-92.351074"/>
    <coord lat="38.984699" lng="-92.343092"/>
    <coord lat="38.981163" lng="-92.342234"/>
    <coord lat="38.984663" lng="-92.3335"/>
    <coord lat="38.993472" lng="-92.333179"/>
    <coord lat="38.994206" lng="-92.350645"/>
</subdivision>

My issue is that the javascript I am using to try and draw each shape onto the map is returning odd coordinates. using an alert, I can see that the array that is meant to store the coordinates for the "new google.maps.Polygon" is returning the first latitude and longitude pair for each shape and drawing a line segment as opposed to the full polygon. The problematic javascript is below.

function initialize() {
    var mapOptions = {
        ...
    };

    var map = new google.maps.Map(document.getElementById('map-canvas'),
  mapOptions);
    var arr = new Array();
    var polygons = [];

    downloadUrl("subdivision-coordinates.php", function(data) {
        var xml = data.responseXML;
        var subdivision = xml.documentElement.getElementsByTagName("subdivision");
        for (var i = 0; i < subdivision.length; i++) {
            var coordinates = xml.documentElement.getElementsByTagName("subdivision")[i].getElementsByTagName("coord");
            arr.push( new google.maps.LatLng(
                    parseFloat(coordinates[i].getAttribute("lat")),
                    parseFloat(coordinates[i].getAttribute("lng"))
            ));

            polygons.push(new google.maps.Polygon({
                paths: arr,
                strokeColor: '#FF0000',
                strokeOpacity: 0.8,
                strokeWeight: 2,
                fillColor: '#FF0000',
                fillOpacity: 0.35
            }));
            polygons[polygons.length-1].setMap(map);
        }
  });
}
function downloadUrl(url, callback) {
  ..blah..blah stuff from google
}
function doNothing() {}
google.maps.event.addDomListener(window, 'load', initialize);

The issue seems to be clearly related to how I am pushing the data into the array "arr". I've tried a few different methods of handling it and nothing seems to be working (I am admittedly a novice when it comes to javascript). Any advice would be greatly appreciated!

geocodezip · Accepted Answer · 2021-12-01T02:32:50.883

The google.maps.Polygon paths property takes an array of arrays of google.maps.LatLngs. You need to process through each subdivision as its own array and either push it as a separate path into the one polygon or (as below) create a new polygon for each.

    var subdivision = xml.getElementsByTagName("subdivision");
    for (var i = 0; i < subdivision.length; i++) {
        arr = [];
        var coordinates = xml.documentElement.getElementsByTagName("subdivision")[i].getElementsByTagName("coord");
        for (var j=0; j < coordinates.length; j++) {
          arr.push( new google.maps.LatLng(
                parseFloat(coordinates[j].getAttribute("lat")),
                parseFloat(coordinates[j].getAttribute("lng"))
          ));
            
          bounds.extend(arr[arr.length-1])
        }
        polygons.push(new google.maps.Polygon({
            paths: arr,
            strokeColor: '#FF0000',
            strokeOpacity: 0.8,
            strokeWeight: 2,
            fillColor: '#FF0000',
            fillOpacity: 0.35
        }));
        polygons[polygons.length-1].setMap(map);
    }

working fiddle

code snippet:

function initialize() {
  var mapOptions = {
    zoom: 5,
    center: new google.maps.LatLng(40, -117),
    mapTypeId: google.maps.MapTypeId.ROADMAP
  };

  var map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions);
  var arr = new Array();
  var polygons = [];
  var bounds = new google.maps.LatLngBounds();

  // downloadUrl("subdivision-coordinates.php", function(data) {
  var xml = xmlParse(xmlString);
  var subdivision = xml.getElementsByTagName("subdivision");
  // alert(subdivision.length);
  for (var i = 0; i < subdivision.length; i++) {
    arr = [];
    var coordinates = xml.documentElement.getElementsByTagName("subdivision")[i].getElementsByTagName("coord");
    for (var j = 0; j < coordinates.length; j++) {
      arr.push(new google.maps.LatLng(
        parseFloat(coordinates[j].getAttribute("lat")),
        parseFloat(coordinates[j].getAttribute("lng"))
      ));

      bounds.extend(arr[arr.length - 1])
    }
    polygons.push(new google.maps.Polygon({
      paths: arr,
      strokeColor: '#FF0000',
      strokeOpacity: 0.8,
      strokeWeight: 2,
      fillColor: '#FF0000',
      fillOpacity: 0.35
    }));
    polygons[polygons.length - 1].setMap(map);
  }
  // });
  map.fitBounds(bounds);
}
var xmlString = '<subdivisions><subdivision name="Auburn Hills"><coord lat="39.00748" lng="-92.323222"/><coord lat="39.000843" lng="-92.323523"/><coord lat="39.000509" lng="-92.311592"/><coord lat="39.007513" lng="-92.311378"/><coord lat="39.00748" lng="-92.323222"/></subdivision><subdivision name="Vanderveen"><coord lat="38.994206" lng="-92.350645"/><coord lat="38.985033" lng="-92.351074"/><coord lat="38.984699" lng="-92.343092"/><coord lat="38.981163" lng="-92.342234"/><coord lat="38.984663" lng="-92.3335"/><coord lat="38.993472" lng="-92.333179"/><coord lat="38.994206" lng="-92.350645"/></subdivision><subdivisions>';

/**
 * Parses the given XML string and returns the parsed document in a
 * DOM data structure. This function will return an empty DOM node if
 * XML parsing is not supported in this browser.
 * @param {string} str XML string.
 * @return {Element|Document} DOM.
 */
function xmlParse(str) {
  if (typeof ActiveXObject != 'undefined' && typeof GetObject != 'undefined') {
    var doc = new ActiveXObject('Microsoft.XMLDOM');
    doc.loadXML(str);
    return doc;
  }

  if (typeof DOMParser != 'undefined') {
    return (new DOMParser()).parseFromString(str, 'text/xml');
  }

  return createElement('div', null);
}

google.maps.event.addDomListener(window, 'load', initialize);

#map-canvas,
body,
html {
  height: 100%;
  width: 100%;
}

<script src="http://maps.google.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>
<div id="map-canvas"></div>

Drawing Multiple Polygons on Google Maps API v3 from MySQL database

1 Answers1

Linked