How to draw a path on a map using kml file?

Question

Hi everyone. Can I parse kml file in order to display paths or points in android? Please could you help me with that?

This is kml sample code which I would like to display in android google map:

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2"&gt;
<Document>
<name>Paths</name>
<description>Examples of paths. Note that the tessellate tag is by default
  set to 0. If you want to create tessellated lines, they must be authored
  (or edited) directly in KML.</description>
<Style id="yellowLineGreenPoly">
  <LineStyle>
    <color>7f00ffff</color>
    <width>4</width>
  </LineStyle>
  <PolyStyle>
    <color>7f00ff00</color>
  </PolyStyle>
</Style>
<Placemark>
  <name>Absolute Extruded</name>
  <description>Transparent green wall with yellow outlines</description>
  <styleUrl>#yellowLineGreenPoly</styleUrl>
  <LineString>
    <extrude>1</extrude>
    <tessellate>1</tessellate>
    <altitudeMode>absolute</altitudeMode>
    <coordinates> -112.2550785337791,36.07954952145647,2357
      -112.2549277039738,36.08117083492122,2357
      -112.2552505069063,36.08260761307279,2357
      -112.2564540158376,36.08395660588506,2357
      -112.2580238976449,36.08511401044813,2357
      -112.2595218489022,36.08584355239394,2357
      -112.2608216347552,36.08612634548589,2357
      -112.262073428656,36.08626019085147,2357
      -112.2633204928495,36.08621519860091,2357
      -112.2644963846444,36.08627897945274,2357
      -112.2656969554589,36.08649599090644,2357 
    </coordinates>
    <LineString>
    </Placemark>
    </Document>
    </kml>

When I'm loading this file to standard web google map it displays it nicely but when I'm trying the same thing with android google map it doesn't do that. It just takes me to some locations and that's it. I was thinking of changing listener class. Currently it looks like that:

private class MyLocationListener implements LocationListener 
{
    @Override
    public void onLocationChanged(Location loc) {
        if (loc != null) {
            latitude = (loc.getLatitude() * 1E6);
            longitude = (loc.getLongitude() * 1E6);
             Toast.makeText(getBaseContext(), 
                     "Location changed : Lat: " + latitude + 
                     " Lng: " + longitude, 
                     Toast.LENGTH_SHORT).show();

             GeoPoint p = new GeoPoint(
                     (int) (loc.getLatitude() * 1E6), 
                     (int) (loc.getLongitude() * 1E6));

             mc.animateTo(p);
             mapView.invalidate();
           }
    }

//---------------------------------------------------------------
    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStatusChanged(String provider, int status, 
        Bundle extras) {
        // TODO Auto-generated method stub
    }

Please can someone tell me what's I'm doing wrong here? Thanks!

Answer 1

In above code, you don't pass the kml data to your mapView anywhere in your code, as far as I can see. To display the route, you should parse the kml data i.e. via SAX parser, then display the route markers on the map.

See the code below for an example, but it's not complete though - just for you as a reference and get some idea.

This is a simple bean I use to hold the route information I will be parsing.

package com.myapp.android.model.navigation;

import java.util.ArrayList;
import java.util.Iterator;


public class NavigationDataSet { 

private ArrayList<Placemark> placemarks = new ArrayList<Placemark>();
private Placemark currentPlacemark;
private Placemark routePlacemark;

public String toString() {
    String s= "";
    for (Iterator<Placemark> iter=placemarks.iterator();iter.hasNext();) {
        Placemark p = (Placemark)iter.next();
        s += p.getTitle() + "\n" + p.getDescription() + "\n\n";
    }
    return s;
}

public void addCurrentPlacemark() {
    placemarks.add(currentPlacemark);
}

public ArrayList<Placemark> getPlacemarks() {
    return placemarks;
}

public void setPlacemarks(ArrayList<Placemark> placemarks) {
    this.placemarks = placemarks;
}

public Placemark getCurrentPlacemark() {
    return currentPlacemark;
}

public void setCurrentPlacemark(Placemark currentPlacemark) {
    this.currentPlacemark = currentPlacemark;
}

public Placemark getRoutePlacemark() {
    return routePlacemark;
}

public void setRoutePlacemark(Placemark routePlacemark) {
    this.routePlacemark = routePlacemark;
}

}

And the SAX Handler to parse the kml:

package com.myapp.android.model.navigation;

import android.util.Log;
import com.myapp.android.myapp;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import com.myapp.android.model.navigation.NavigationDataSet;
import com.myapp.android.model.navigation.Placemark;


public class NavigationSaxHandler extends DefaultHandler{ 

 // =========================================================== 
 // Fields 
 // =========================================================== 

 private boolean in_kmltag = false; 
 private boolean in_placemarktag = false; 
 private boolean in_nametag = false;
 private boolean in_descriptiontag = false;
 private boolean in_geometrycollectiontag = false;
 private boolean in_linestringtag = false;
 private boolean in_pointtag = false;
 private boolean in_coordinatestag = false;

 private StringBuffer buffer;

 private NavigationDataSet navigationDataSet = new NavigationDataSet(); 

 // =========================================================== 
 // Getter & Setter 
 // =========================================================== 

 public NavigationDataSet getParsedData() {
      navigationDataSet.getCurrentPlacemark().setCoordinates(buffer.toString().trim());
      return this.navigationDataSet; 
 } 

 // =========================================================== 
 // Methods 
 // =========================================================== 
 @Override 
 public void startDocument() throws SAXException { 
      this.navigationDataSet = new NavigationDataSet(); 
 } 

 @Override 
 public void endDocument() throws SAXException { 
      // Nothing to do
 } 

 /** Gets be called on opening tags like: 
  * <tag> 
  * Can provide attribute(s), when xml was like: 
  * <tag attribute="attributeValue">*/ 
 @Override 
 public void startElement(String namespaceURI, String localName, 
           String qName, Attributes atts) throws SAXException { 
      if (localName.equals("kml")) { 
           this.in_kmltag = true;
      } else if (localName.equals("Placemark")) { 
           this.in_placemarktag = true; 
           navigationDataSet.setCurrentPlacemark(new Placemark());
      } else if (localName.equals("name")) { 
           this.in_nametag = true;
      } else if (localName.equals("description")) { 
          this.in_descriptiontag = true;
      } else if (localName.equals("GeometryCollection")) { 
          this.in_geometrycollectiontag = true;
      } else if (localName.equals("LineString")) { 
          this.in_linestringtag = true;              
      } else if (localName.equals("point")) { 
          this.in_pointtag = true;          
      } else if (localName.equals("coordinates")) {
          buffer = new StringBuffer();
          this.in_coordinatestag = true;                        
      }
 } 

 /** Gets be called on closing tags like: 
  * </tag> */ 
 @Override 
 public void endElement(String namespaceURI, String localName, String qName) 
           throws SAXException { 
       if (localName.equals("kml")) {
           this.in_kmltag = false; 
       } else if (localName.equals("Placemark")) { 
           this.in_placemarktag = false;

       if ("Route".equals(navigationDataSet.getCurrentPlacemark().getTitle())) 
               navigationDataSet.setRoutePlacemark(navigationDataSet.getCurrentPlacemark());
        else navigationDataSet.addCurrentPlacemark();

       } else if (localName.equals("name")) { 
           this.in_nametag = false;           
       } else if (localName.equals("description")) { 
           this.in_descriptiontag = false;
       } else if (localName.equals("GeometryCollection")) { 
           this.in_geometrycollectiontag = false;
       } else if (localName.equals("LineString")) { 
           this.in_linestringtag = false;              
       } else if (localName.equals("point")) { 
           this.in_pointtag = false;          
       } else if (localName.equals("coordinates")) { 
           this.in_coordinatestag = false;
       }
 } 

 /** Gets be called on the following structure: 
  * <tag>characters</tag> */ 
 @Override 
public void characters(char ch[], int start, int length) { 
    if(this.in_nametag){ 
        if (navigationDataSet.getCurrentPlacemark()==null) navigationDataSet.setCurrentPlacemark(new Placemark());
        navigationDataSet.getCurrentPlacemark().setTitle(new String(ch, start, length));            
    } else 
    if(this.in_descriptiontag){ 
        if (navigationDataSet.getCurrentPlacemark()==null) navigationDataSet.setCurrentPlacemark(new Placemark());
        navigationDataSet.getCurrentPlacemark().setDescription(new String(ch, start, length));          
    } else
    if(this.in_coordinatestag){        
        if (navigationDataSet.getCurrentPlacemark()==null) navigationDataSet.setCurrentPlacemark(new Placemark());
        //navigationDataSet.getCurrentPlacemark().setCoordinates(new String(ch, start, length));
        buffer.append(ch, start, length);
    }
} 
}

and a simple placeMark bean:

package com.myapp.android.model.navigation;

public class Placemark {

String title;
String description;
String coordinates;
String address;

public String getTitle() {
    return title;
}
public void setTitle(String title) {
    this.title = title;
}
public String getDescription() {
    return description;
}
public void setDescription(String description) {
    this.description = description;
}
public String getCoordinates() {
    return coordinates;
}
public void setCoordinates(String coordinates) {
    this.coordinates = coordinates;
}
public String getAddress() {
    return address;
}
public void setAddress(String address) {
    this.address = address;
}

}

Finally the service class in my model that calls the calculation:

package com.myapp.android.model.navigation;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import com.myapp.android.myapp;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;

import android.util.Log;

public class MapService {

public static final int MODE_ANY = 0;
public static final int MODE_CAR = 1;
public static final int MODE_WALKING = 2;


public static String inputStreamToString (InputStream in) throws IOException {
    StringBuffer out = new StringBuffer();
    byte[] b = new byte[4096];
    for (int n; (n = in.read(b)) != -1;) {
        out.append(new String(b, 0, n));
    }
    return out.toString();
}


public static NavigationDataSet calculateRoute(Double startLat, Double startLng, Double targetLat, Double targetLng, int mode) {
    return calculateRoute(startLat + "," + startLng, targetLat + "," + targetLng, mode);
}

public static NavigationDataSet calculateRoute(String startCoords, String targetCoords, int mode) {
    String urlPedestrianMode = "http://maps.google.com/maps?" + "saddr=" + startCoords + "&daddr="
            + targetCoords + "&sll=" + startCoords + "&dirflg=w&hl=en&ie=UTF8&z=14&output=kml";

    Log.d(myapp.APP, "urlPedestrianMode: "+urlPedestrianMode);

    String urlCarMode = "http://maps.google.com/maps?" + "saddr=" + startCoords + "&daddr="
            + targetCoords + "&sll=" + startCoords + "&hl=en&ie=UTF8&z=14&output=kml";

    Log.d(myapp.APP, "urlCarMode: "+urlCarMode);

    NavigationDataSet navSet = null;
    // for mode_any: try pedestrian route calculation first, if it fails, fall back to car route
    if (mode==MODE_ANY||mode==MODE_WALKING) navSet = MapService.getNavigationDataSet(urlPedestrianMode);
    if (mode==MODE_ANY&&navSet==null||mode==MODE_CAR) navSet = MapService.getNavigationDataSet(urlCarMode);
    return navSet;
}

/**
 * Retrieve navigation data set from either remote URL or String
 * @param url
 * @return navigation set
 */
public static NavigationDataSet getNavigationDataSet(String url) {

    // urlString = "http://192.168.1.100:80/test.kml";
    Log.d(myapp.APP,"urlString -->> " + url);
    NavigationDataSet navigationDataSet = null;
    try
        {           
        final URL aUrl = new URL(url);
        final URLConnection conn = aUrl.openConnection();
        conn.setReadTimeout(15 * 1000);  // timeout for reading the google maps data: 15 secs
        conn.connect();

        /* Get a SAXParser from the SAXPArserFactory. */
        SAXParserFactory spf = SAXParserFactory.newInstance(); 
        SAXParser sp = spf.newSAXParser(); 

        /* Get the XMLReader of the SAXParser we created. */
        XMLReader xr = sp.getXMLReader();

        /* Create a new ContentHandler and apply it to the XML-Reader*/ 
        NavigationSaxHandler navSax2Handler = new NavigationSaxHandler(); 
        xr.setContentHandler(navSax2Handler); 

        /* Parse the xml-data from our URL. */ 
        xr.parse(new InputSource(aUrl.openStream()));

        /* Our NavigationSaxHandler now provides the parsed data to us. */ 
        navigationDataSet = navSax2Handler.getParsedData(); 

        /* Set the result to be displayed in our GUI. */ 
        Log.d(myapp.APP,"navigationDataSet: "+navigationDataSet.toString());

    } catch (Exception e) {
        // Log.e(myapp.APP, "error with kml xml", e);
        navigationDataSet = null;
    }   

    return navigationDataSet;
}

}

Drawing:

/**
 * Does the actual drawing of the route, based on the geo points provided in the nav set
 *
 * @param navSet     Navigation set bean that holds the route information, incl. geo pos
 * @param color      Color in which to draw the lines
 * @param mMapView01 Map view to draw onto
 */
public void drawPath(NavigationDataSet navSet, int color, MapView mMapView01) {

    Log.d(myapp.APP, "map color before: " + color);        

    // color correction for dining, make it darker
    if (color == Color.parseColor("#add331")) color = Color.parseColor("#6C8715");
    Log.d(myapp.APP, "map color after: " + color);

    Collection overlaysToAddAgain = new ArrayList();
    for (Iterator iter = mMapView01.getOverlays().iterator(); iter.hasNext();) {
        Object o = iter.next();
        Log.d(myapp.APP, "overlay type: " + o.getClass().getName());
        if (!RouteOverlay.class.getName().equals(o.getClass().getName())) {
            // mMapView01.getOverlays().remove(o);
            overlaysToAddAgain.add(o);
        }
    }
    mMapView01.getOverlays().clear();
    mMapView01.getOverlays().addAll(overlaysToAddAgain);

    String path = navSet.getRoutePlacemark().getCoordinates();
    Log.d(myapp.APP, "path=" + path);
    if (path != null && path.trim().length() > 0) {
        String[] pairs = path.trim().split(" ");

        Log.d(myapp.APP, "pairs.length=" + pairs.length);

        String[] lngLat = pairs[0].split(","); // lngLat[0]=longitude lngLat[1]=latitude lngLat[2]=height

        Log.d(myapp.APP, "lnglat =" + lngLat + ", length: " + lngLat.length);

        if (lngLat.length<3) lngLat = pairs[1].split(","); // if first pair is not transferred completely, take seconds pair //TODO 

        try {
            GeoPoint startGP = new GeoPoint((int) (Double.parseDouble(lngLat[1]) * 1E6), (int) (Double.parseDouble(lngLat[0]) * 1E6));
            mMapView01.getOverlays().add(new RouteOverlay(startGP, startGP, 1));
            GeoPoint gp1;
            GeoPoint gp2 = startGP;

            for (int i = 1; i < pairs.length; i++) // the last one would be crash
            {
                lngLat = pairs[i].split(",");

                gp1 = gp2;

                if (lngLat.length >= 2 && gp1.getLatitudeE6() > 0 && gp1.getLongitudeE6() > 0
                        && gp2.getLatitudeE6() > 0 && gp2.getLongitudeE6() > 0) {

                    // for GeoPoint, first:latitude, second:longitude
                    gp2 = new GeoPoint((int) (Double.parseDouble(lngLat[1]) * 1E6), (int) (Double.parseDouble(lngLat[0]) * 1E6));

                    if (gp2.getLatitudeE6() != 22200000) { 
                        mMapView01.getOverlays().add(new RouteOverlay(gp1, gp2, 2, color));
                        Log.d(myapp.APP, "draw:" + gp1.getLatitudeE6() + "/" + gp1.getLongitudeE6() + " TO " + gp2.getLatitudeE6() + "/" + gp2.getLongitudeE6());
                    }
                }
                // Log.d(myapp.APP,"pair:" + pairs[i]);
            }
            //routeOverlays.add(new RouteOverlay(gp2,gp2, 3));
            mMapView01.getOverlays().add(new RouteOverlay(gp2, gp2, 3));
        } catch (NumberFormatException e) {
            Log.e(myapp.APP, "Cannot draw route.", e);
        }
    }
    // mMapView01.getOverlays().addAll(routeOverlays); // use the default color
    mMapView01.setEnabled(true);
}

This is the RouteOverlay class:

package com.myapp.android.activity.map.nav;

import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.RectF;

import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;
import com.google.android.maps.Projection;

public class RouteOverlay extends Overlay { 

private GeoPoint gp1;
private GeoPoint gp2;
private int mRadius=6;
private int mode=0;
private int defaultColor;
private String text="";
private Bitmap img = null;

public RouteOverlay(GeoPoint gp1,GeoPoint gp2,int mode) { // GeoPoint is a int. (6E)
    this.gp1 = gp1;
    this.gp2 = gp2;
    this.mode = mode;
    defaultColor = 999; // no defaultColor
}

public RouteOverlay(GeoPoint gp1,GeoPoint gp2,int mode, int defaultColor) {
    this.gp1 = gp1;
    this.gp2 = gp2;
    this.mode = mode;
    this.defaultColor = defaultColor;
}

public void setText(String t) {
    this.text = t;
}

public void setBitmap(Bitmap bitmap) { 
    this.img = bitmap;
}

public int getMode() {
    return mode;
}

@Override
public boolean draw (Canvas canvas, MapView mapView, boolean shadow, long when) {
    Projection projection = mapView.getProjection();
    if (shadow == false) {
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        Point point = new Point();
        projection.toPixels(gp1, point);
        // mode=1：start
        if(mode==1) {
            if(defaultColor==999)
            paint.setColor(Color.BLACK); // Color.BLUE
            else
            paint.setColor(defaultColor);
            RectF oval=new RectF(point.x - mRadius, point.y - mRadius,
            point.x + mRadius, point.y + mRadius);
            // start point
            canvas.drawOval(oval, paint);
        }
        // mode=2：path
        else if(mode==2) {
            if(defaultColor==999)
            paint.setColor(Color.RED);
            else
            paint.setColor(defaultColor);
            Point point2 = new Point();
            projection.toPixels(gp2, point2);
            paint.setStrokeWidth(5);
            paint.setAlpha(defaultColor==Color.parseColor("#6C8715")?220:120);
            canvas.drawLine(point.x, point.y, point2.x,point2.y, paint);
        }
        /* mode=3：end */
        else if(mode==3) {
            /* the last path */

            if(defaultColor==999)
                paint.setColor(Color.BLACK);  // Color.GREEN
            else
                paint.setColor(defaultColor);

            Point point2 = new Point();
            projection.toPixels(gp2, point2);
            paint.setStrokeWidth(5);
            paint.setAlpha(defaultColor==Color.parseColor("#6C8715")?220:120);
            canvas.drawLine(point.x, point.y, point2.x,point2.y, paint);
            RectF oval=new RectF(point2.x - mRadius,point2.y - mRadius,
            point2.x + mRadius,point2.y + mRadius);
            /* end point */
            paint.setAlpha(255);
            canvas.drawOval(oval, paint);
        }
    }
    return super.draw(canvas, mapView, shadow, when);
}

}