Question

I’m working on google maps API V3. I need to place markers dynamically on the map and I need to differentiate each marker in any method.

Either I need to have numbered markers or different colored markers. Please suggest a way to finish my project. I am using pure javascript in a JSP page.

Answer 1

Here is an example of marker categories from Mike Williams’ v2 tutorial translated to the google maps API v3. I have examples for the v2 API of using lettered markers and numbered markers or numbered markers defined in xml that could be translated to v3.

code snippet:

// this variable will collect the html which will eventually be placed in the side_bar 
var side_bar_html = "";

var gmarkers = [];
var gicons = [];
var map = null;

var infowindow = new google.maps.InfoWindow({
  size: new google.maps.Size(150, 50)
});


gicons["red"] = new google.maps.MarkerImage("http://www.geocodezip.com/mapIcons/marker_red.png",
  // This marker is 20 pixels wide by 34 pixels tall.
  new google.maps.Size(20, 34),
  // The origin for this image is 0,0.
  new google.maps.Point(0, 0),
  // The anchor for this image is at 9,34.
  new google.maps.Point(9, 34));
// Marker sizes are expressed as a Size of X,Y
// where the origin of the image (0,0) is located
// in the top left of the image.

// Origins, anchor positions and coordinates of the marker
// increase in the X direction to the right and in
// the Y direction down.

var iconImage = new google.maps.MarkerImage('http://www.geocodezip.com/mapIcons/marker_red.png',
  // This marker is 20 pixels wide by 34 pixels tall.
  new google.maps.Size(20, 34),
  // The origin for this image is 0,0.
  new google.maps.Point(0, 0),
  // The anchor for this image is at 9,34.
  new google.maps.Point(9, 34));
var iconShadow = new google.maps.MarkerImage('http://www.google.com/mapfiles/shadow50.png',
  // The shadow image is larger in the horizontal dimension
  // while the position and offset are the same as for the main image.
  new google.maps.Size(37, 34),
  new google.maps.Point(0, 0),
  new google.maps.Point(9, 34));
// Shapes define the clickable region of the icon.
// The type defines an HTML <area> element 'poly' which
// traces out a polygon as a series of X,Y points. The final
// coordinate closes the poly by connecting to the first
// coordinate.
var iconShape = {
  coord: [9, 0, 6, 1, 4, 2, 2, 4, 0, 8, 0, 12, 1, 14, 2, 16, 5, 19, 7, 23, 8, 26, 9, 30, 9, 34, 11, 34, 11, 30, 12, 26, 13, 24, 14, 21, 16, 18, 18, 16, 20, 12, 20, 8, 18, 4, 16, 2, 15, 1, 13, 0],
  type: 'poly'
};

function getMarkerImage(iconColor) {
  if ((typeof(iconColor) == "undefined") || (iconColor == null)) {
    iconColor = "red";
  }
  if (!gicons[iconColor]) {
    gicons[iconColor] = new google.maps.MarkerImage("http://www.geocodezip.com/mapIcons/marker_" + iconColor + ".png",
      // This marker is 20 pixels wide by 34 pixels tall.
      new google.maps.Size(20, 34),
      // The origin for this image is 0,0.
      new google.maps.Point(0, 0),
      // The anchor for this image is at 6,20.
      new google.maps.Point(9, 34));
  }
  return gicons[iconColor];

}

function category2color(category) {
  var color = "red";
  switch (category) {
    case "theatre":
      color = "blue";
      break;
    case "golf":
      color = "green";
      break;
    case "info":
      color = "yellow";
      break;
    default:
      color = "red";
      break;
  }
  return color;
}

gicons["theatre"] = getMarkerImage(category2color("theatre"));
gicons["golf"] = getMarkerImage(category2color("golf"));
gicons["info"] = getMarkerImage(category2color("info"));

// A function to create the marker and set up the event window
function createMarker(latlng, name, html, category) {
  var contentString = html;
  var marker = new google.maps.Marker({
    position: latlng,
    icon: gicons[category],
    shadow: iconShadow,
    map: map,
    title: name,
    zIndex: Math.round(latlng.lat() * -100000) << 5
  });
  // === Store the category and name info as a marker properties ===
  marker.mycategory = category;
  marker.myname = name;
  gmarkers.push(marker);

  google.maps.event.addListener(marker, 'click', function() {
    infowindow.setContent(contentString);
    infowindow.open(map, marker);
  });
}

// == shows all markers of a particular category, and ensures the checkbox is checked ==
function show(category) {
  for (var i = 0; i < gmarkers.length; i++) {
    if (gmarkers[i].mycategory == category) {
      gmarkers[i].setVisible(true);
    }
  }
  // == check the checkbox ==
  document.getElementById(category + "box").checked = true;
}

// == hides all markers of a particular category, and ensures the checkbox is cleared ==
function hide(category) {
  for (var i = 0; i < gmarkers.length; i++) {
    if (gmarkers[i].mycategory == category) {
      gmarkers[i].setVisible(false);
    }
  }
  // == clear the checkbox ==
  document.getElementById(category + "box").checked = false;
  // == close the info window, in case its open on a marker that we just hid
  infowindow.close();
}

// == a checkbox has been clicked ==
function boxclick(box, category) {
  if (box.checked) {
    show(category);
  } else {
    hide(category);
  }
  // == rebuild the side bar
  makeSidebar();
}

function myclick(i) {
  google.maps.event.trigger(gmarkers[i], "click");
}


// == rebuilds the sidebar to match the markers currently displayed ==
function makeSidebar() {
  var html = "";
  for (var i = 0; i < gmarkers.length; i++) {
    if (gmarkers[i].getVisible()) {
      html += '<a href="javascript:myclick(' + i + ')">' + gmarkers[i].myname + '<\/a><br>';
    }
  }
  document.getElementById("side_bar").innerHTML = html;
}

function initialize() {
  var myOptions = {
    zoom: 11,
    center: new google.maps.LatLng(53.8363, -3.0377),
    mapTypeId: google.maps.MapTypeId.ROADMAP
  }
  map = new google.maps.Map(document.getElementById("map"), myOptions);


  google.maps.event.addListener(map, 'click', function() {
    infowindow.close();
  });



  // Read the data
  // downloadUrl("categories.xml", function(doc) { // doesn't work cross-domain, load the xml from a string
  var xml = xmlParse(xmlString);
  var markers = xml.documentElement.getElementsByTagName("marker");

  for (var i = 0; i < markers.length; i++) {
    // obtain the attribues of each marker
    var lat = parseFloat(markers[i].getAttribute("lat"));
    var lng = parseFloat(markers[i].getAttribute("lng"));
    var point = new google.maps.LatLng(lat, lng);
    var address = markers[i].getAttribute("address");
    var name = markers[i].getAttribute("name");
    var html = "<b>" + name + "<\/b><p>" + address;
    var category = markers[i].getAttribute("category");
    // create the marker
    var marker = createMarker(point, name, html, category);
  }

  // == show or hide the categories initially ==
  show("theatre");
  hide("golf");
  hide("info");
  // == create the initial sidebar ==
  makeSidebar();
  // });
}
google.maps.event.addDomListener(window, 'load', initialize);
var xmlString = '<markers> <marker name="Grand Theatre" address="33 Church St, Blackpool, Lancashire, FY1 1HT" lng="-3.053102" lat="53.817260" category="theatre" /> <marker name="Claremont Theatre Club" address="Burwood Dr, Blackpool, Lancashire, FY3 8NS" lng="-3.049690" lat="53.829649" category="theatre" /> <marker name="Pendle Productions" address="249 Hawes Side La, Blackpool, Lancashire, FY4 4AA" lng="-3.030698" lat="53.794399" category="theatre" /> <marker name="Tram Shed Theatre" address="7 Moor Pk Av, Blackpool, Lancashire, FY2 0LT" lng="-3.034974" lat="53.845938" category="theatre" /> <marker name="Thornton Little Theatre" address="Fleetwood Road North, Thornton Cleveleys, FY5 3SZ" lng="-3.010607" lat="53.872058" category="theatre" /> <marker name="Barbara Jackson Arts" address="Rossall La, Fleetwood, Lancashire, FY7 8JP" lng="-3.033960" lat="53.897928" category="theatre" /> <marker name="North Shore Golf Club" address="Devonshire Rd, Blackpool, Lancashire, FY2 0RD" lng="-3.043305" lat="53.839898" category="golf" /> <marker name="St Annes Old Links" address="Highbury Road East, Lytham St. Annes, Lancashire, FY8 2LD" lng="-3.038407" lat="53.762917" category="golf" /> <marker name="Fairhaven Golf Club" address="Oakwood Av, Lytham St. Annes, Lancashire, FY8 4JU" lng="-2.983218" lat="53.742781" category="golf" /> <marker name="Green Drive Golf Club" address="Ballam Rd, Lytham St. Annes, Lancashire, FY8 4LE" lng="-2.959530" lat="53.745971" category="golf" /> <marker name="Fleetwood Golf Club" address="Princes Wy, Fleetwood, Lancashire, FY7 8AF" lng="-3.042973" lat="53.917606" category="golf" /> <marker name="Knott End Golf Club" address="Wyre Side, Knott End-on-Sea, Poulton-le-Fylde, Lancashire, FY6 0AA" lng="-2.997062" lat="53.923200" category="golf" /> <marker name="Tourist Information 1" address="1 Clifton St, Blackpool, Lancashire, FY1 1LY" lng="-3.054529" lat="53.818775" category="info" /> <marker name="Tourist Information 2" address="Thornton-Cleveleys, Lancashire, FY5 1WA" lng="-3.042989" lat="53.876079" category="info" /> <marker name="Tourist Information 3" address="Victoria Rd West, Thornton-Cleveleys, Lancashire, FY5 1AJ" lng="-3.041668" lat="53.877403" category="info" /> <marker name="Tourist Information 4" address="St. Annes Rd West, Lytham St. Annes, Lancashire, FY8 1SA" lng="-3.031074" lat="53.752122" category="info" /> <marker name="Tourist Information 5" address="The Esplanade, Fleetwood, Lancashire, FY7 6DL" lng="-3.006366" lat="53.926970" category="info" /> <marker name="Tourist Information 6" address="10-12 York St, Blackpool, Lancashire, FY1 5AQ" lng="-3.052919" lat="53.810556" category="info" /></markers>';
/**
 * 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);
}

html,
body,
#map_canvas {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
}

<script src="https://maps.google.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>
<!-- you can use tables or divs for the overall layout -->
<table border=1>
  <tr>
    <td>
      <div id="map" style="width: 550px; height: 450px"></div>
    </td>
    <td valign="top" style="width:150px; text-decoration: underline; color: #4444ff;">
      <div id="side_bar"></div>
    </td>
  </tr>
</table>
<form action="#">
  Theatres: <input type="checkbox" id="theatrebox" onclick="boxclick(this,'theatre')" /> &nbsp;&nbsp; Golf Courses: <input type="checkbox" id="golfbox" onclick="boxclick(this,'golf')" /> &nbsp;&nbsp; Tourist Information: <input type="checkbox" id="infobox"
    onclick="boxclick(this,'info')" /><br />
</form>