Getting Issue drawing Line in Map between Two locations in android sdk

Question

package com.hands;

import java.net.HttpURLConnection;
import java.net.URL;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import android.os.Bundle;
import android.util.Log;

import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;

public class DrawlineActivity extends MapActivity {
     MapView myMapView = null;
     MapController myMC = null;
     GeoPoint geoPoint = null;
     @Override
     public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      setContentView(R.layout.main);
      myMapView = (MapView) findViewById(R.id.mapview);

      geoPoint = null;
      myMapView.setSatellite(false);
      double fromLat = 12.303534;
      double fromLong = 76.64611;
      double toLat = 12.9715987;
      double toLong = 77.5945627;

      String sourceLat = Double.toString(fromLat);
      String sourceLong = Double.toString(fromLong);
      String destinationLat = Double.toString(toLat);
      String destinationLong = Double.toString(toLong);

  String pairs[] = getDirectionData(sourceLat,sourceLong, destinationLat, destinationLong );
//The above line pairs[] retrieving null value. Showing as NULL POINTER EXCEPTION
      String[] lngLat = pairs[0].split(",");

      // STARTING POINT
      GeoPoint startGP = new GeoPoint((int) (Double.parseDouble(lngLat[1]) * 1E6), (int) (Double.parseDouble(lngLat[0]) * 1E6));

      myMC = myMapView.getController();
      geoPoint = startGP;
      myMC.setCenter(geoPoint);
      myMC.setZoom(10);
      myMapView.getOverlays().add(new DirectionPathOverlay(startGP, startGP));

      // NAVIGATE THE PATH

      GeoPoint gp1;
      GeoPoint gp2 = startGP;

      for (int i = 1; i < pairs.length; i++) {
       lngLat = pairs[i].split(",");
       gp1 = gp2;
       // watch out! For GeoPoint, first:latitude, second:longitude

       gp2 = new GeoPoint((int) (Double.parseDouble(lngLat[1]) * 1E6),(int) (Double.parseDouble(lngLat[0]) * 1E6));
       myMapView.getOverlays().add(new DirectionPathOverlay(gp1, gp2));
       Log.d("xxx", "pair:" + pairs[i]);
      }

      // END POINT
      myMapView.getOverlays().add(new DirectionPathOverlay(gp2, gp2));

      myMapView.getController().animateTo(startGP);
      myMapView.setBuiltInZoomControls(true);
      myMapView.displayZoomControls(true);

     }

     @Override
     protected boolean isRouteDisplayed() {
      // TODO Auto-generated method stub
      return false;
     }

Layout

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello" />

   <com.google.android.maps.MapView
           android:id="@+id/mapview"
             android:layout_width="fill_parent"
             android:layout_height="fill_parent"
             android:apiKey="034BXAeVNYe1Ob063cZUpablCB_0y7xjEGD3RhQ"
             />

Logcat Details

08-10 09:03:20.216: W/dalvikvm(305): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
08-10 09:03:20.246: E/AndroidRuntime(305): FATAL EXCEPTION: main
08-10 09:03:20.246: E/AndroidRuntime(305): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hands/com.hands.DrawlineActivity}: java.lang.NullPointerException
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.ActivityThread.access$2300(ActivityThread.java:125)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.os.Handler.dispatchMessage(Handler.java:99)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.os.Looper.loop(Looper.java:123)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.ActivityThread.main(ActivityThread.java:4627)
08-10 09:03:20.246: E/AndroidRuntime(305):       at java.lang.reflect.Method.invokeNative(Native Method)
08-10 09:03:20.246: E/AndroidRuntime(305):       at java.lang.reflect.Method.invoke(Method.java:521)
08-10 09:03:20.246: E/AndroidRuntime(305):       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-10 09:03:20.246: E/AndroidRuntime(305):       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-10 09:03:20.246: E/AndroidRuntime(305):       at dalvik.system.NativeStart.main(Native Method)
08-10 09:03:20.246: E/AndroidRuntime(305): Caused by: java.lang.NullPointerException
08-10 09:03:20.246: E/AndroidRuntime(305):       at com.hands.DrawlineActivity.getDirectionData(DrawlineActivity.java:111)
08-10 09:03:20.246: E/AndroidRuntime(305):       at com.hands.DrawlineActivity.onCreate(DrawlineActivity.java:44)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-10 09:03:20.246: E/AndroidRuntime(305):       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
08-10 09:03:20.246: E/AndroidRuntime(305):       ... 11 more

Updated With getDirection Method code

package com.hands;

import java.net.HttpURLConnection; import java.net.URL;

import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document; import org.w3c.dom.Node; import org.w3c.dom.NodeList;

import android.os.Bundle; import android.util.Log;

import com.google.android.maps.GeoPoint; import com.google.android.maps.MapActivity; import com.google.android.maps.MapController; import com.google.android.maps.MapView;

public class DrawlineActivity extends MapActivity { MapView myMapView = null; MapController myMC = null; GeoPoint geoPoint = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);

  setContentView(R.layout.main);
  myMapView = (MapView) findViewById(R.id.mapview);

  geoPoint = null;
  myMapView.setSatellite(false);
  double fromLat = 12.303534;
  double fromLong = 76.64611;
  double toLat = 12.9715987;
  double toLong = 77.5945627;

  String sourceLat = Double.toString(fromLat);
  String sourceLong = Double.toString(fromLong);
  String destinationLat = Double.toString(toLat);
  String destinationLong = Double.toString(toLong);

  String pairs[] = getDirectionData(sourceLat,sourceLong, destinationLat, destinationLong );
  String[] lngLat = pairs[0].split(",");

  // STARTING POINT
  GeoPoint startGP = new GeoPoint((int) (Double.parseDouble(lngLat[1]) * 1E6), (int) (Double.parseDouble(lngLat[0]) * 1E6));

  myMC = myMapView.getController();
  geoPoint = startGP;
  myMC.setCenter(geoPoint);
  myMC.setZoom(10);
  myMapView.getOverlays().add(new DirectionPathOverlay(startGP, startGP));

  // NAVIGATE THE PATH

  GeoPoint gp1;
  GeoPoint gp2 = startGP;

  for (int i = 1; i < pairs.length; i++) {
   lngLat = pairs[i].split(",");
   gp1 = gp2;
   // watch out! For GeoPoint, first:latitude, second:longitude

   gp2 = new GeoPoint((int) (Double.parseDouble(lngLat[1]) * 1E6),(int) (Double.parseDouble(lngLat[0]) * 1E6));
   myMapView.getOverlays().add(new DirectionPathOverlay(gp1, gp2));
   Log.d("xxx", "pair:" + pairs[i]);
  }

  // END POINT
  myMapView.getOverlays().add(new DirectionPathOverlay(gp2, gp2));

  myMapView.getController().animateTo(startGP);
  myMapView.setBuiltInZoomControls(true);
  myMapView.displayZoomControls(true);

 }

 @Override
 protected boolean isRouteDisplayed() {
  // TODO Auto-generated method stub
  return false;
 }

 private String[] getDirectionData(String sourceLat, String sourceLong, String destinationLat, String destinationLong) {


  String urlString = "http://maps.google.com/maps?f=d&hl=en&" +"saddr="+sourceLat+","+sourceLong+"&daddr="+destinationLat+","+destinationLong + "&ie=UTF8&0&om=0&output=kml";
  Log.d("URL", urlString);
  Document doc = null;
  HttpURLConnection urlConnection = null;
  URL url = null;
  String pathConent = "";

  try {

   url = new URL(urlString.toString());
   urlConnection = (HttpURLConnection) url.openConnection();
   urlConnection.setRequestMethod("GET");
   urlConnection.setDoOutput(true);
   urlConnection.setDoInput(true);
   urlConnection.connect();
   DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
   DocumentBuilder db = dbf.newDocumentBuilder();
   doc = db.parse(urlConnection.getInputStream());

  } catch (Exception e) {
  }

  NodeList nl = doc.getElementsByTagName("LineString");
  for (int s = 0; s < nl.getLength(); s++) {
   Node rootNode = nl.item(s);
   NodeList configItems = rootNode.getChildNodes();
   for (int x = 0; x < configItems.getLength(); x++) {
    Node lineStringNode = configItems.item(x);
    NodeList path = lineStringNode.getChildNodes();
    pathConent = path.item(0).getNodeValue();
   }
  }
  String[] tempContent = pathConent.split(" ");
  return tempContent;
 }

}

John J Smith John J Smith · Accepted Answer · 2012-08-10T18:54:18

As the logcat explains, you are getting a NullPointerException when you call the method getDirectionData(). This method is not shown in the code above. Can you add this method so we can see what the problem is?

Edit: Thanks for adding your getDirectionData() method. Its still not clear where the problem is but one issue is the fact that you have an empty catch block - this will swallow exceptions and then you carry on processing code. For example, if the line

doc = db.parse(urlConnection.getInputStream());

throws an exception or returns null, then you try to get the NodeList from a null object - this would give you your null pointer exception. I recommend putting a breakpoint at the start of this method and stepping through it, examining the variables as you go. This will identify the source of the problem.

Getting Issue drawing Line in Map between Two locations in android sdk

1 Answers