howto: dynamically update markers from JSON on google maps

Question

I am trying to update the location of a marker with out refreshing the whole page. I have tried to use setTimeout(function() however I am having no luck..

here is my code I have so far..

thanks in advance

function initialize() {
    var mapOptions = {
       center: new google.maps.LatLng(35.66, -80.50),
      zoom: 8,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    var map = new google.maps.Map(document.getElementById("map-canvas"),
        mapOptions);



 var json = (function () { 
        var json = null; 
            $.ajax({ 
                'async': false, 
                'global': false, 
                'url': "getjson.php", 
                'dataType': "json", 
                'success': function (data) {
                 json = data; } }); 

            return json;})(); 
for (var i = 0, length = json.length; i < length; i++) {

  var data = json[i],
  latLng = new google.maps.LatLng(data.lat, data.lng); 
var marker = new google.maps.Marker({
position: latLng,
map: map,
title: data.title
});

}

var infoWindow = new google.maps.InfoWindow();


google.maps.event.addListener(marker, "click", function(e) {
infoWindow.setContent(data.description);
infoWindow.open(map, marker);
});


(function(marker, data) {


google.maps.event.addListener(marker, "click", function(e) {
infoWindow.setContent(data.description);
infoWindow.open(map, marker);
});

})(marker, data);



  }

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

here is my JSON output.

[{"lat":35.6606376,"lng":-80.5048653,"content":"bca"},    {"lat":42.6799504,"lng":-36.4949205,"content":"abc"}]

Answer 1

I would suggest using setInterval rather than setTimeout.

Here is some code that simulates an update via JSON in a fiddle, using your provided JSON with the required "description" member added for each marker:

var map = null;
var gmarkers = [];
var intervalNumber = 0;
setInterval(function () {
    new Request.JSON({
        url: '/echo/json/',
        data: {
            json: JSON.encode([{
                "lat": 35.6606376 + (0.01 * intervalNumber),
                    "lng": -80.5048653 + (0.1 * intervalNumber),
                    "content": "bca",
                "description":"first marker"
            }, {
                "lat": 42.6799504 + (0.01 * intervalNumber),
                    "lng": -36.4949205 - (0.1 * intervalNumber),
                    "content": "abc",
                "description": "second marker"
            }]),
            delay: 3
        },
        onSuccess: function (response) {
            update_map(response);
            intervalNumber++;
        }
    }).send();
}, 5000);
update_map = function (data) {
    var bounds = new google.maps.LatLngBounds();

    // delete all existing markers first
    for (var i = 0; i < gmarkers.length; i++) {
        gmarkers[i].setMap(null);
    }
    gmarkers = [];

    // add new markers from the JSON data
    for (var i = 0, length = data.length; i < length; i++) {
        latLng = new google.maps.LatLng(data[i].lat, data[i].lng);
        bounds.extend(latLng);
        var marker = new google.maps.Marker({
            position: latLng,
            map: map,
            title: data[i].title
        });
        var infoWindow = new google.maps.InfoWindow();
        google.maps.event.addListener(marker, "click", function (e) {
            infoWindow.setContent(data.description+"<br>"+marker.getPosition().toUrlValue(6));
            infoWindow.open(map, marker);
        });
        (function (marker, data) {
            google.maps.event.addListener(marker, "click", function (e) {
                infoWindow.setContent(data.description+"<br>"+marker.getPosition().toUrlValue(6));
                infoWindow.open(map, marker);
            });
        })(marker, data[i]);
        gmarkers.push(marker);
    }

    // zoom the map to show all the markers, may not be desirable.
    map.fitBounds(bounds);
};

function initialize() {
    // initialize the map on page load.
    var mapOptions = {
        center: new google.maps.LatLng(35.66, -80.50),
        zoom: 8,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    map = new google.maps.Map(document.getElementById("map-canvas"),
    mapOptions);

    // add the markers to the map if they have been loaded already.
    if (gmarkers.length > 0) {
        for (var i = 0; i < gmarkers.length; i++) {
            gmarkers[i].setMap(map);
        }
    }
}

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

Answer 2

https://developers.google.com/maps/documentation/javascript/reference

markerObject.setPosition(latlng:LatLng|LatLngLiteral)

I don't think you need to redraw the map, but in case you do:

google.maps.event.trigger(mapObject, 'resize');