Advanced Example1

Java API for KML - Advanced Example1

[ The concept ] [ Google's Chart API used by JAK ] [ Get statistic data and generate charts ]

The concept

This series of more sophisticated JAK examples is trying to show the capabilities what is possible with KML in Java. They show the usage of JAK for generating some nice-looking KML files, which can be viewed with Google Earth.

Important!
JAK only works if all dependencies are resolved! That are mainly JAK and JAXB! For further instructions check out the FAQ.

Google's Chart API used by JAK

This example generates a KML file with placemarks and charts for each continent. The chart shows the perentual coverage of the continent's landmass and it is generated with Google's Chart API.

Figure 1: Placemarks with a chart of the surface of the earth for each continent.

Get statistic data and generate charts

The statistical data is gathered from Wikipedia and additionally shown in Table 1.

Continent	LatLon	Percent of total landmass
Asia	93.24607775062842, 47.49808862281773	29.5%
Africa	19.44601806124206, 10.13133611111111	20.4%
North America	-103.5286299241638, 41.26035225962401	16.5%
South America	59.96161780270248, -13.27347674076888	12.0%
Europe	14.45531426360271, 47.26208181151567	6.8%
Australia	135.0555272486322, -26.23824399654937	5.9%

Table 1: The land mass coverage in percent of each continent.

Listing 1 shows the structure of the "Create-A-Pie-Chart-Of-The-Land_Coverage_of_Each_Continent"TM. It uses a solely for this example created helper function called createPlacemarkWithChart (). It is a convenience method to save a lot of boilerplate code and it is used to create the different placemarks filled with the statistical data gathered in Table 1. The structure of createPlacemarkWithChart () is shown below in Listing 2.

Listing 1: Generates Placemarks with a chart of the surface of the earth for each continent.

final Kml kml = new Kml();
    Document doc = kml.createAndSetDocument().withName("JAK Example1").withOpen(true);

    // create a Folder
    Folder folder = doc.createAndAddFolder();
    folder.withName("Continents with Earth's surface").withOpen(true);
    
    // create Placemark elements
    createPlacemarkWithChart(doc, folder, 93.24607775062842, 47.49808862281773, "Asia", 30);
    createPlacemarkWithChart(doc, folder, 19.44601806124206, 10.13133611111111, "Africa", 20);
    createPlacemarkWithChart(doc, folder, -103.5286299241638, 41.26035225962401, "North America", 17);
    createPlacemarkWithChart(doc, folder, -59.96161780270248, -13.27347674076888, "South America", 12);
    createPlacemarkWithChart(doc, folder, 14.45531426360271, 47.26208181151567, "Europe", 7);
    createPlacemarkWithChart(doc, folder, 135.0555272486322, -26.23824399654937, "Australia", 6);
   
    // print and save
    kml.marshal(new File("advancedexample1.kml"));

The createPlacemarkWithChart ()-method generates and set a placemark object, with the given statistical data . The Icon and Style objects (color and size of the text and icon) are saved to the root element. The placemark is created and set to the given folder.

Listing 2: The createPlacemarkWithChart()-method

/**
 * @param document structure of the KML file
 * @param folder to add continent
 * @param longitude of the continent
 * @param latitude of the continent
 * @param continentName or name of the placemark
 * @param coveredLandmass in percent
 */
private static void createPlacemarkWithChart(Document document, Folder folder, double longitude, double latitude, 
    String continentName, int coveredLandmass) {

	int remainingLand = 100 - coveredLandmass;
	Icon icon = new Icon()
	    .withHref("http://chart.apis.google.com/chart?chs=380x200&chd=t:" + coveredLandmass + "," + remainingLand + "&cht=p&chf=bg,s,ffffff00");
	Style style = document.createAndAddStyle();
	style.withId("style_" + continentName) // set the stylename to use this style from the placemark
	    .createAndSetIconStyle().withScale(5.0).withIcon(icon); // set size and icon
	style.createAndSetLabelStyle().withColor("ff43b3ff").withScale(5.0); // set color and size of the continent name

	Placemark placemark = folder.createAndAddPlacemark();
	// use the style for each continent
	placemark.withName(continentName)
	    .withStyleUrl("#style_" + continentName)
	    // 3D chart imgae
	    .withDescription(
	        "<![CDATA[<img src=\"http://chart.apis.google.com/chart?chs=430x200&chd=t:" + coveredLandmass + "," + remainingLand + "&cht=p3&chl=" + continentName + "|remaining&chtt=Earth's surface\" />")
	    // coordinates and distance (zoom level) of the viewer
	    .createAndSetLookAt().withLongitude(longitude).withLatitude(latitude).withAltitude(0).withRange(12000000);
	
	placemark.createAndSetPoint().addToCoordinates(longitude, latitude); // set coordinates
}

The full example is contained in JAK's sources (/JavaAPIforKML/src/test/java/de/micromata/jak/examples/Example1.java).
The resulting KML-file can be downloaded here: advancedexample1.kml.

Java API for KML | @Google