Android development - GPS not working - Application hangs when co-ordinates sent - android-emulator

Question

Problem Background:
I am somewhat new to Android development. All I'm trying to do, for now, is to get GPS coordinates from the GPS device of the phone and display them on Google Maps or just in a TextView, or whatever. The main task is to get them.
I've read a number of tutorials. I'm using
- Android 2.3.3
- API level 10
- Eclipse 3.6.1
- Windows 7
Problem Description :
I have written a class GeoUpdateHandler which implements LocationListener and implements its methods onLocationChange() etc. And in MyMapsActivity, I use the regular requestLocationUpdates of the LocationManager to get periodic updates.
When I run the application, I send GPS coordinates from the Emulator Control of Eclipse (Window --> Show View --> Other --> Android --> Emulator Control) to send Longitude and Latitude. As soon as the emulated device gets the coordinates, the application hangs. Nothing happens and the cursor changes to the blue circle (which signifies thinking/stuck) and nothing happens. If I use locationManager.getLastKnownLocation(String provider), it gets null. Obviously, because there IS no last known location. It gets stuck before knowing one!
I have tried sending the coordinates through telnet as well. (cmd --> telnet localhost 5554 --> geo fix . But the same thing happens.
I have tried starting the device independent of the application, sending the coordinates, and then starting the application. But the same thing happens when I run the application: it hangs.
The following code HelloItemizedOverlay is taken from Android's MapView tutorial and works fine with manually given coordinates. The problem arises when GPS location is tried to be retrieved.
public class MyMapsActivity extends MapActivity
{
private MapController mapController;
private MapView mapView;
private LocationManager locationManager;
LinearLayout linLayout;
MapView mView;
List<Overlay> mapOverlays;
Drawable drawable;
HelloItemizedOverlay itemizedOverlay;
GeoUpdateHandler handler;
Location location;
public void onCreate(Bundle bundle)
{
super.onCreate(bundle);
setContentView(R.layout.main); // bind the layout to the activity
mView = (MapView) findViewById(R.id.mapview);
mView.setBuiltInZoomControls(true);
mapOverlays = mView.getOverlays();
drawable = this.getResources().getDrawable(R.drawable.icon);
itemizedOverlay = new HelloItemizedOverlay(drawable);
mapController = mView.getController();
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
handler = new GeoUpdateHandler();
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 3000, 0, handler);
location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
GeoPoint point = new GeoPoint((int)location.getLongitude(),(int)location.getLatitude());
OverlayItem overlayitem = new OverlayItem(point, "", "");
mView.setBuiltInZoomControls(true);
itemizedOverlay.addOverlay(overlayitem);
mapOverlays.add(itemizedOverlay);
mapController.setZoom(8);
mapController.animateTo(point);
}
#Override
protected boolean isRouteDisplayed()
{
return false;
}
public class GeoUpdateHandler implements LocationListener
{
#Override
public void onLocationChanged(Location location)
{
int lat = (int) (location.getLatitude());
int lng = (int) (location.getLongitude());
GeoPoint point = new GeoPoint(lat, lng);
mapController.animateTo(point); // mapController.setCenter(point);
}
#Override
public void onProviderDisabled(String provider)
{
}
#Override
public void onProviderEnabled(String provider)
{
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras)
{
}
}
#Override
protected void onResume()
{
handler = new GeoUpdateHandler();
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, 0, handler);
super.onResume();
}
}

Answer 1

According to this, the Geopoint constructor takes (latitude * 1e6, longitude * 1e6) as parameters ; whereas you put (longitude, latitude) when calling getLastKnownLocation, and you forgot the scale factor in the other call (in onLocationChanged). Latitude and logitude are not scaled in Location objects.
Anyways, this error should only result in displaying a blue map ((0,0) being in the atlantic ocean), so there may be other problems.
Edit:
1/ in replay to your comment, if you mix up longitude and latitude, you may get an unexisting point (latitude always stays within [-90°,90°] whereas longitude can vary in [-180°,180°])
2/ there is a bug in SDK 2.3 (API level 9), which makes the emulator crash when sending mock locations. Don't know wether it is true for 2.3.3 (lvl 10), but I used 2.1u1 (lvl 7) to test.
3/ The following code works for me :
package test.testmap;
import java.util.List;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;
import com.google.android.maps.OverlayItem;
public class MyMapsActivity extends MapActivity
{
private MapController mapController;
private LocationManager locationManager;
LinearLayout linLayout;
MapView mView;
List<Overlay> mapOverlays;
Drawable drawable;
HelloItemizedOverlay itemizedOverlay;
GeoUpdateHandler handler;
Location location;
public void onCreate(Bundle bundle)
{
super.onCreate(bundle);
setContentView(R.layout.main); // bind the layout to the activity
drawable = this.getResources().getDrawable(R.drawable.icon);
itemizedOverlay = new HelloItemizedOverlay(drawable);
mView = (MapView) findViewById(R.id.mapview);
mView.setBuiltInZoomControls(true);
mapOverlays = mView.getOverlays();
mapOverlays.add(itemizedOverlay);
mapController = mView.getController();
}
#Override
protected boolean isRouteDisplayed()
{
return false;
}
public class GeoUpdateHandler implements LocationListener
{
#Override
public void onLocationChanged(Location location)
{
Log.d(this.getClass().getName(),"onLocationChanged : lat = "+location.getLatitude()+" lon = "+location.getLongitude());
int lat = (int) Math.round(location.getLatitude()*1.0e6);
int lng = (int) Math.round(location.getLongitude()*1.0e6);
GeoPoint point = new GeoPoint(lat, lng);
itemizedOverlay.addOverlay(new OverlayItem(point, "", ""));
mapController.animateTo(point);
mapController.setZoom(8);
}
#Override
public void onProviderDisabled(String provider)
{
Log.d(this.getClass().getName(),"onProviderDisabled");
}
#Override
public void onProviderEnabled(String provider)
{
Log.d(this.getClass().getName(),"onProviderEnabled");
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras)
{
Log.d(this.getClass().getName(),"onStatusChanged");
}
}
#Override
protected void onResume()
{
handler = new GeoUpdateHandler();
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, 0, handler);
super.onResume();
}
}