displaying markers on a google map in javascript

Question

I am a Javascript beginner and I am trying to create markers on a google map. So first of all I am getting GPS co-ordinates from a database which I am splitting apart to get the lattitude and longlitude values, then I am adding them to 2 separate listboxes called lstBoxLatGPS and lstBoxLongGPS in c#

foreach (string item in GPSLatList)
    {
        lstBoxLatGPS.Items.Add(item);
    }
foreach (string item in GPSLongList)
    {
        lstBoxLongGPS.Items.Add(item);
    }

Now in Javascript I want to take the items in the listboxes and create markers on the map I have 2 functions:

        function GetLatValues() 
        {
            var arrValues= new Array();
            var listBox = document.getElementById("<%=lstBoxLatGPS.ClientID%>");
            for (var i = 0; i < listBox.options.length; i++) 
            {arrValues[i]= listbox.options[i].text }
            return (arrValues);
        }
        function GetLongValues() 
        {
            var arrValues= new Array();
            var listBox = document.getElementById("%=lstBoxLongGPS.ClientID%>");
            for (var i = 0; i < listBox.options.length; i++) 
            {arrValues[i]= listbox.options[i].text }
            return (arrValues);
        }

then to add the arrays to made the markers:

        function initialize()
        {
            var mapCanvas = document.getElementById('map-canvas');
            var mapOptions =
            {
                center: new google.maps.LatLng(-28.4792811, 24.6722268),
                zoom: 6,
                mapTypeId: google.maps.MapTypeId.ROADMAP
            }
            var map = new google.maps.Map(mapCanvas, mapOptions);
            map.set('styles', [
  {
      "featureType": "landscape",
      "stylers": [
        { "color": "#c9d7bb" }
      ]
  }, {
      "featureType": "administrative.province",
      "elementType": "labels.text",
      "stylers": [
        { "visibility": "on" },
        { "color": "#ffc23d" }
      ]
  }, {
      "featureType": "poi.attraction",
      "stylers": [
        { "visibility": "on" },
        { "color": "#9be586" }
      ]
  }, {
      "featureType": "administrative.province",
      "elementType": "geometry",
      "stylers": [
        { "visibility": "on" },
        { "color": "#000000" },
        { "weight": 3.2 }
      ]
  }
            ]);

            var GPSLatArray = new Array();
            var GPSLongArray = new Array();
            GPSLatArray = GetLatValues();
            GPSLongArray = GetLongValues();

            for (var i = 0; i < GPSLatArray.length; i++)
            {
                var marker = new google.maps.Marker({position: GPSLatArray[i],GPSLongArray[i] });
                marker.setMap(map);
            }
        }
        google.maps.event.addDomListener(window, 'load', initialize);

When the map is supposed to be displayed, it is just blank, not showing the map at all.

Answer 1

您需要在aspx页面中添加div才能显示地图。

<div class="img-thumbnail" id="map-canvas" style="width: 369px; height: 289px;"></div>

Answer 2

我使用Artem.Google包创建了地图，现在可以使用了。