App Error 104 uncaught : runtime exception while running blackberry application - blackberry

Question

I have created one application to get My location coordinates using GPS after deploying my code in simulator i am getting above error with explanation -
uncaught exception:pushmodalscreen called by a non-event thread
I am not able to figure out whats going wrong.
/**
* GPSDemo.java
*
* Copyright © 1998-2011 Research In Motion Ltd.
*
* Note: For the sake of simplicity, this sample application may not leverage
* resource bundles and resource strings. However, it is STRONGLY recommended
* that application developers make use of the localization features available
* within the BlackBerry development platform to ensure a seamless application
* experience across a variety of languages and geographies. For more information
* on localizing your application, please refer to the BlackBerry Java Development
* Environment Development Guide associated with this release.
*/
package com.gps;
import java.util.*;
import javax.microedition.location.*;
import net.rim.device.api.command.*;
import net.rim.device.api.gps.*;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.util.*;
import net.rim.blackberry.api.invoke.*;
import net.rim.blackberry.api.maps.*;
import net.rim.blackberry.api.menuitem.*;
/**
* This application acts as a simple travel computer, recording route
* coordinates, speed and altitude. Recording begins as soon as the
* application is invoked.
*/
public class GPSScreen extends UiApplication
{
// Represents the number of updates over which altitude is calculated, in seconds
private static final int GRADE_INTERVAL = 5;
private static final long ID = 0x5d459971bb15ae7aL;
// Represents period of the position query, in seconds
private static int _interval = 1;
private double _latitude;
private double _longitude;
private LocationProvider _locationProvider;
private GPSDemoScreen _screen;
private MapView _mapview = new MapView();
/**
* Entry point for application
*
* #param args Command line arguments (not used)
*/
public static void main(String[] args)
{
// Create a new instance of the application and make the currently
// running thread the application's event dispatch thread.
new GPSScreen().enterEventDispatcher();
}
/**
* Create a new GPSDemo object
*/
public GPSScreen()
{
_screen = new GPSDemoScreen();
_screen.setTitle("GPS Demo");
// Attempt to start the location listening thread
if(startLocationUpdate())
{
_screen.setState(_locationProvider.getState());
}
// Render the screen
pushScreen(_screen);
}
/**
* Invokes the Location API with Standalone criteria
*
* #return True if the <code>LocationProvider</code> was successfully started, false otherwise
*/
private boolean startLocationUpdate()
{
boolean returnValue = false;
if(!(GPSInfo.getDefaultGPSMode() == GPSInfo.GPS_MODE_NONE))
{
try
{
Criteria criteria = new Criteria();
criteria.setCostAllowed(false);
_locationProvider = LocationProvider.getInstance(criteria);
if(_locationProvider != null)
{
/*
* Only a single listener can be associated with a provider,
* and unsetting it involves the same call but with null.
* Therefore, there is no need to cache the listener
* instance request an update every second.
*/
_locationProvider.setLocationListener(new LocationListenerImpl(), _interval, -1, -1);
returnValue = true;
}
else
{
invokeLater(new Runnable()
{
public void run()
{
Dialog.alert("Failed to obtain a location provider, exiting...");
System.exit(0);
}
});
}
}
catch(final LocationException le)
{
invokeLater(new Runnable()
{
public void run()
{
Dialog.alert("Failed to instantiate LocationProvider object, exiting..." + le.toString());
System.exit(0);
}
});
}
}
else
{
invokeLater(new Runnable()
{
public void run()
{
Dialog.alert("GPS is not supported on this device, exiting...");
System.exit(0);
}
});
}
return true;
}
/**
* Implementation of the LocationListener interface. Listens for updates to
* the device location and displays the results.
*/
private class LocationListenerImpl implements LocationListener
{
/**
* #see javax.microedition.location.LocationListener#locationUpdated(LocationProvider,Location)
*/
public void locationUpdated(LocationProvider provider, Location location)
{
if(location.isValid())
{
_longitude = location.getQualifiedCoordinates().getLongitude();
_latitude = location.getQualifiedCoordinates().getLatitude();
_mapview.setZoom(Integer.parseInt("0.1"));
try
{
int latitude = (int) (100000 * _latitude);
int longitude = (int) (100000 * _longitude);
if (latitude > 9000000 || latitude < -9000000 || longitude >= 18000000 || longitude < -18000000)
{
throw new IllegalArgumentException ();
}
_mapview.setLatitude(latitude);
_mapview.setLongitude(longitude);
// Invoke BlackBerry Maps application with provided MapView object.
Invoke.invokeApplication(Invoke.APP_TYPE_MAPS, new MapsArguments(_mapview));
}
catch(RuntimeException re)
{
// An exception is thrown when any of the following occur :
// Latitude is invalid : Valid range: [-90, 90]
// Longitude is invalid : Valid range: [-180, 180)
// Minus sign between 2 numbers.
Dialog.alert("Temporary Unavailable Service");
}
}
}
/**
* #see javax.microedition.location.LocationListener#providerStateChanged(LocationProvider, int)
*/
public void providerStateChanged(LocationProvider provider, int newState)
{
if(newState == LocationProvider.TEMPORARILY_UNAVAILABLE)
{
provider.reset();
}
_screen.setState(newState);
}
}
/**
* The main screen to display the current GPS information
*/
private final class GPSDemoScreen extends MainScreen
{
TextField _statusTextField;
/**
* Create a new GPSDemoScreen object
*/
GPSDemoScreen()
{
// Initialize UI
_statusTextField = new TextField(Field.NON_FOCUSABLE);
}
/**
* Display the state of the GPS service
*
* #param newState The state to display
*/
public void setState(final int newState)
{
UiApplication.getUiApplication().invokeLater(new Runnable()
{
/**
* #see java.lang.Runnable#run()
*/
public void run()
{
switch(newState)
{
case LocationProvider.AVAILABLE:
_statusTextField.setText("Available");
break;
case LocationProvider.OUT_OF_SERVICE:
_statusTextField.setText("Out of Service");
break;
case LocationProvider.TEMPORARILY_UNAVAILABLE:
_statusTextField.setText("Temporarily Unavailable");
break;
}
}
});
}
/**
* #see net.rim.device.api.ui.Screen#close()
*/
public void close()
{
if(_locationProvider != null)
{
_locationProvider.reset();
_locationProvider.setLocationListener(null, -1, -1, -1);
}
super.close();
}
}
}

Answer 1

I've seen that error when Dialog.alert() is used outside of the event thread. Looking at your code, I see LocationListenerImpl.locationUpdated assumes it is running on the event thread. If it is not, the UI update code would throw an exception, and then your exception handler will try to display a dialog, and that will fail as well.