Revision as of 12:47, 16 July 2012

This article explains how to read a structured XML file and create map markers based on the data.

Introduction

Sometimes it is useful to have the data for a map, e.g. markers, in a separate file. This article provides an example which you can use to generate map content from an XML file. The example uses JavaScript and jQuery.

Prerequisites

• Nokia Maps API supported web browser (basically any modern web browser).
• jQuery downloaded and installed.
• Change the directory names for your own version of the example, if needed.

Example code

Note that the example code - Markersxml.zip - leaves you room to implement your own InfoBubbles and some other functionality is there if you need it, otherwise you can remove it; for e.g. the behaviour of the map and availability of components. Feel free to copy and modify for your own purposes!

Header

Both the Nokia Maps API for JavaScript and the jQuery library need to be referenced in the header.

<script type="text/javascript" src="http://api.maps.nokia.com/2.2.1/jsl.js" charset="utf-8"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>

Body

The Map is set up in init() the usual manner.

function init(){
 
// Here we create an Nokia Maps within a Container. 
mapContainer = document.getElementById("map");
myInfoBubbles = new nokia.maps.map.component.InfoBubbles();
 
myMap = nokia.maps.map,     
                map = new myMap.Display(mapContainer, {
                    center: [52.59, 13.3], zoomLevel: 10,
                    components: [ new myMap.component.Behavior(),
                                  new nokia.maps.map.component.ZoomBar(),
                                  new nokia.maps.map.component.Overview(),                             
                                  new nokia.maps.map.component.TypeSelector(),     
                                  new nokia.maps.map.component.ScaleBar(),
                  myInfoBubbles ]
                });
 
// Define the XML filename to read that contains the marker data
placeMarkersOnMaps('markers.xml'); 
}

When the HTML page body section is loaded the placeMarkersOnMaps() method will be called. This function gets passed the marker XML data file name. The location of the XML file is relative to the URL of the html page.

Note: Both files must be hosted on a server for this function to work. The err method will fire if the file cannot be accessed.

function placeMarkersOnMaps(filename) 
{
var counter = 0;
$.ajax({
    type: "GET",
    url: filename ,
    dataType: "xml",
    success: parseXml,
              error : err
  });
 
}
function err (){
		alert("An Error has occurred.");
}

The parseXml() function is the meat of the example. It uses standard jQuery parsing to retrieve the elements from the XML file.

function parseXml(xml)
{
	var container = new nokia.maps.map.Container();
	$(xml).find("marker").each(function(){
 
			//Read the name, address, latitude and longitude for each Marker
			var nme = $(this).find('name').text();
			var address = $(this).find('address').text();
			var lat = $(this).find('lat').text();
			var lng = $(this).find('lng').text();
 
			//Put each marker on the map as the data has been read.
 
			var markerCoords = new nokia.maps.geo.Coordinate(parseFloat(lat), parseFloat(lng));    
 
			var marker = new nokia.maps.map.StandardMarker(markerCoords, {text:nme});
			container.objects.add(marker);      
 
		});
		// Add the marker container .
		map.objects.add(container);
		// Zoom into the markers.
 
alert("Markers have been loaded. Hit OK to zoom the map into the area covering the markers.");
 
map.zoomTo(container.getBoundingBox(), false);
 
}

Example XML file

The file to be parsed is in the following format - the full XML file can be found in Media:Markersxml.zip

<?xml version="1.0"?>
    <markers>
        <marker>
            <name>M1</name>
            <address>ADDRESS 1</address>
            <lat>52.516617</lat>
            <lng>13.377675</lng>
        </marker>
 
        .... etc
</markers>

Summary

The following screenshot shows how the XML has been parsed

Edit the script and file for your own purposes, hope you find this article useful.

Alternative Solution

Since the latest version of the Nokia Maps API is able to natively render KML files, it would make sense to transform the XML into KML using XSLT. You can copy the markers.xml file from Media:Markersxml.zip into an XSLT Editor and use the the XSLT stylesheet described below.The KML can then be loaded directly onto a map using the code from the Loading a KML file example on the Developer's Playground.

<?xml version="1.0" encoding="ISO-8859-1"?>
<!-- Edited by XMLSpy® -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 
<xsl:template match="markers">
  <Document>
      <xsl:for-each select="marker">
      <Placemark>
        <name><xsl:value-of select="name"/></name>
        <address><xsl:value-of select="address"/></address>
        <coordinates>
           <xsl:value-of select="lat"/>,<xsl:value-of select="lng"/>,0
        </coordinates>
      </Placemark>
      </xsl:for-each>
  </Document>
</xsl:template>
</xsl:stylesheet>

For more on Nokia Maps API

Please check out the Nokia Maps API full documentation and API reference here:

• http://api.maps.nokia.com/

You may also access the interactive Nokia Maps API playground,

• http://api.maps.nokia.com/en/playground/env/desktop/