Develop Reference

Using GPS on Services

On this code i want to get the gps location every 3 seconds. but when i run this program on my device it tells me that latitude and longitude are both 0 every time. how should i handle this problem?
and what is the looper task ?? it gives me error when i donot use it
public class LocationService extends Service {
final static String TAG = "MyService";
double latitude ;
double Longitude ;
LocationManager lm;
LocationListener ll;
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
Log.d(TAG, "onCreate");
super.onCreate();
}
#Override
public int onStartCommand(Intent intent, int flags, int startId) {
new Thread() {
public void run() {
Looper.prepare();
while(true){
lm = (LocationManager) getSystemService(LOCATION_SERVICE);
ll = new MyLocationListener();
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER,
0, 0, ll);
//when i log here , it gives me wronganswer
Log.d(TAG,Double.toString(latitude));
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
return super.onStartCommand(intent, flags, startId);
}
#Override
public void onDestroy() {
Log.d(TAG, "OnDestroy");
super.onDestroy();
}
class MyLocationListener implements LocationListener{
#Override
public void onLocationChanged(Location location) {
//when i log here , it gives me correct answer
double lat = location.getLatitude();
double lon = location.getLongitude();
latitude = lat;
Longitude = lon;
}
#Override
public void onProviderDisabled(String arg0) {
}
#Override
public void onProviderEnabled(String arg0) {
}
#Override
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
}
};
}

When you get location from GPS, it can take some time, because GPS module needs to find satellites. So you need to wait couple or few minutes while GPS module find satellites. If WI-FI location provider available you can get location more quick.
Additional info about location providers you can find here: http://developer.android.com/guide/topics/location/strategies.html
Since Android has
GPS_PROVIDER and NETWORK_PROVIDER
you can register to both and start fetch events from onLocationChanged(Location location) from two at the same time. So far so good. Now the question do we need two results or we should take the best. As I know GPS_PROVIDER results have better accuracy than NETWORK_PROVIDER.
for example you have location listener:
LocationListener locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
//here you get locations from both providers
}
public void onProviderDisabled(String provider) {
}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
};
YOu need to do something like that:
LocationManager lm = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0,locationListener);
lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0,locationListener);
but before registering you need to check is these providers available on this device, like that:
boolean network_enabled = lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
boolean gps_enabled = lm.isProviderEnabled(LocationManager.GPS_PROVIDER);

Access LocationManager/ LocationListener from class

I'm kinda lost here: In my main activity, I register a LocationManager and connect it to a LocationListener to use myLocation.getLatitude() and such.
Now I need to use the Location- methods from another class.
I can't use those object from another class because I cant intantiate the main activity.
I can't use getters to pass the L.Manager or L.Listener around, because those are non- static again.
So, in general, how do i access objects that I created in the main activity?
Any hints on how to organize this better? Is the LocationListener class within the main activity class a stupid thing to do in general?
public class URNavActivity extends Activity
{
public LocationManager mlocManager;
public LocationListener mlocListener;
...
}
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
mResourceProxy = new DefaultResourceProxyImpl(getApplicationContext());
actVar=this;
initGraph();
setMap();
gpsEnable();
initMyLocation();
getItems();
initOverlay();
}
public void gpsEnable ()
{
mlocManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
mlocListener = new MyLocationListener();
mlocManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, mlocListener);
}
public class MyLocationListener implements LocationListener
{
#Override
public void onLocationChanged(Location loc)
{
loc.getLatitude();
loc.getLongitude();
myMap.getController().setCenter(new GeoPoint(lati, longi));
}

First and foremost your LocationListener should not be part of an activity. Activities have a clearly defined lifecycle and can come into being, and be destroyed, by the Android framework on an as-needed basis. Therefore the instance variables of your Activity will need to be re-initialised in your activity's onResume() method, making them completely unsuitable for long-term storage.
So. Start by creating a sticky service to manage the starting and stopping of location updates. Being sticky means that the service instance hangs around between invocations and therefore you can reliably use instance variables and know that they will retain their values until the service is terminated. This service should also implement the LocationListener interface, and now it can store the Location notified to it when onLocationChanged is invoked:
public class LocationService extends Service implements LocationListener {
private LocationManager locationManager;
private Location location;
#Override
public int onStartCommand(final Intent intent, final int flags, final int startId) {
Logging.i(CLAZZ, "onHandleIntent", "invoked");
if (intent.getAction().equals("startListening")) {
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
}
else {
if (intent.getAction().equals("stopListening")) {
locationManager.removeUpdates(this);
locationManager = null;
}
}
return START_STICKY;
}
#Override
public IBinder onBind(final Intent intent) {
return null;
}
public void onLocationChanged(final Location location) {
this.location = location;
// TODO this is where you'd do something like context.sendBroadcast()
}
public void onProviderDisabled(final String provider) {
}
public void onProviderEnabled(final String provider) {
}
public void onStatusChanged(final String arg0, final int arg1, final Bundle arg2) {
}
}
Now you have a service you can start and stop the location updates as you need them. This also allows you to continue to receive and process location changes even when your application is not in the foreground, if that is what you want.
You now have two choices on how to make that Location information available: Use context.sendBroadcast() to propagate the new Location to (for example) an activity, or use the bound service approach to allow other classes to invoke the exposed API and obtain the Location. See http://developer.android.com/guide/topics/fundamentals/bound-services.html for more details on creating a bound service.
Note that there are many other aspects to listening for location updates that I have not included here, for the sake of clarity.

I would offer two elegant ways to access your object from anywhere:
use a Singleton design pattern
use ProjectApp class. This class can be accessed from any activity simply by calling getApplication().
ProjectApp app = (ProjectApp)getApplication();
I used a combination of the two:
public class MyApp extends Application {
private MyLocation mMyLocation;
#Override
public void onCreate() {
super.onCreate();
mMyLocation = new MyLocation();
mMyLocation.getLocation(this, GlobalData.getInstance(), true);
}
}
You can see that GlobalData is a singleton class that implements LocationResult interface, meaning that it will send the updated location to this object.
When I need to get the updated location, I take it from GlobalData.
Here is MyLocation class implementation (I used some code from here and made some changes:
package com.pinhassi.android.utilslib;
import java.util.Timer;
import java.util.TimerTask;
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
public class MyLocation {
private Timer timer1;
private LocationManager lm;
private LocationResult locationResult;
private boolean gps_enabled=false;
private boolean network_enabled=false;
private boolean mContinuesUpdates;
private int decimalAccuracy;
/**
* Class constructor
*/
public MyLocation(){
decimalAccuracy = 0;
}
public boolean getLocation(Context context, LocationResult result, boolean continuesUpdates)
{
mContinuesUpdates = continuesUpdates;
//I use LocationResult callback class to pass location value from MyLocation to user code.
locationResult=result;
if(lm==null)
lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
//exceptions will be thrown if provider is not permitted.
try{gps_enabled=lm.isProviderEnabled(LocationManager.GPS_PROVIDER);}catch(Exception ex){}
try{network_enabled=lm.isProviderEnabled(LocationManager.NETWORK_PROVIDER);}catch(Exception ex){}
//don't start listeners if no provider is enabled
if(!gps_enabled && !network_enabled)
return false;
if(gps_enabled)
lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListenerGps);
if(network_enabled)
lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListenerNetwork);
timer1=new Timer();
timer1.schedule(new GetLastLocation(), 20000);
return true;
}
LocationListener locationListenerGps = new LocationListener() {
public void onLocationChanged(Location location) {
timer1.cancel();
locationResult.gotLocation(getDecimalAccurated(location));
if (!mContinuesUpdates)
lm.removeUpdates(this);
lm.removeUpdates(locationListenerNetwork);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
};
LocationListener locationListenerNetwork = new LocationListener() {
public void onLocationChanged(Location location) {
timer1.cancel();
locationResult.gotLocation(getDecimalAccurated(location));
if (!mContinuesUpdates)
lm.removeUpdates(this);
lm.removeUpdates(locationListenerGps);
}
public void onProviderDisabled(String provider) {}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle extras) {}
};
class GetLastLocation extends TimerTask {
#Override
public void run() {
lm.removeUpdates(locationListenerGps);
lm.removeUpdates(locationListenerNetwork);
Location net_loc=null, gps_loc=null;
if(gps_enabled)
gps_loc=lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if(network_enabled)
net_loc=lm.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
//if there are both values use the latest one
if(gps_loc!=null && net_loc!=null){
if(gps_loc.getTime()>net_loc.getTime())
locationResult.gotLocation(getDecimalAccurated(gps_loc));
else
locationResult.gotLocation(getDecimalAccurated(net_loc));
return;
}
if(gps_loc!=null){
locationResult.gotLocation(getDecimalAccurated(gps_loc));
return;
}
if(net_loc!=null){
locationResult.gotLocation(getDecimalAccurated(net_loc));
return;
}
locationResult.gotLocation(null);
}
}
/**
* called when the GPS returns a location.
* can be called multiple times as the location is updated
*/
public interface LocationResult {
public void gotLocation(Location location);
}
/**
* sets location result accuracy
* #param n number of places after the point. negative value or 0 means not set.
*/
public void setDecimalAccuracy(int n)
{
this.decimalAccuracy = n;
}
private Location getDecimalAccurated(Location location) {
if (decimalAccuracy > 0){
double accuracy = Math.pow(10, this.decimalAccuracy);
int ix;
ix = (int)(location.getLatitude() * accuracy);
location.setLatitude(((double)ix)/accuracy);
ix = (int)(location.getLongitude() * accuracy);
location.setLongitude(((double)ix)/accuracy);
}
return location;
}
}

I'll talk in general since I had the same issue:
How to manage the LocationListener and lit this listener access the activity ..
This was my try :
The Listener :
public class MyLocationListener implements LocationListener{
ProgressDialog dialog;
LocationManager locManager;
Context context;
public MyLocationListener (Context context,ProgressDialog dialog){
this.context = context;
this.dialog = dialog;
}
public void startSearch() {
locManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
// If the network provider works run it , else try GPS provider
// TODO : what happens if GPS and Network providers are not suuported ??
if(!locManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER) )
locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0,
0, this);
else
locManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0,
0, this);
dialog = new ProgressDialog(context);
dialog.setTitle("");
dialog.setMessage(context.getString(R.string.pleaseWait));
dialog.setButton(context.getString(R.string.cancel), new DialogInterface.OnClickListener()
{
public void onClick(DialogInterface dialog, int which)
{
locManager.removeUpdates(MyLocationListener .this);
dialog.dismiss();
return;
}
});
dialog.show();
}
// Location Listener implementation
// read Android doc for more info
// this methods is triggered when new location ( latitiude and longitude ) is found by the system
private void updateWithNewLocation(Location location) {
if (location != null) {
double lat = location.getLatitude();
double lng = location.getLongitude();
//THIS IS MY ACTIVITY
MainActivity mainActivity = (MainActivity) context;
mainActivity.init();
} else {
//this.setSummary( "No location found" );
}
// remove the listener , we don't need it anymore
locManager.removeUpdates(this);
dialog.hide();
}
public void onLocationChanged(Location location) {
updateWithNewLocation(location);
}
public void onProviderDisabled(String provider) {
updateWithNewLocation(null);
}
public void onProviderEnabled(String provider) {
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
}
init the listener in the MainActivity like this :
ProgressDialog dialog;
.
.
.
new MyLocationListener (this, dialog).startSearch();
I don't know if that help ? but that was my solution ...

Best error handling approach for GPS lookup in Android?

I'm beta testing my first Android app and have had a few users mention that when they attempt to lookup by GPS it hangs. In order to improve error handling around this I wanted to get the opinion of people who have apps in the wild.
My current activity does the following to kick off the lookup
findViewById(R.id.gpsButton).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
LocationManager mlocManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
MyLocationListener mlocListener = new MyLocationListener();
Criteria locationCriteria = new Criteria();
locationCriteria.setAccuracy(Criteria.ACCURACY_FINE);
mlocManager.requestLocationUpdates(mlocManager.getBestProvider(locationCriteria, true), 0, 0, mlocListener);
}
});
The implementation of my custom location lookup class is below
public class MyLocationListener implements LocationListener {
private boolean alreadyLocatedDevice;
private ProgressDialog dialog;
public MyLocationListener() {
this.dialog = ProgressDialog.show(LocationLookup.this, "", "Loading...");
}
#Override
public void onProviderDisabled(String provider) {
this.dialog.dismiss();
DialogHelper.showDialogWithMessageAndTitle("", "You don't currently have location services turned on", LocationLookup.this);
}
#Override
public void onLocationChanged(android.location.Location location) {
if (!alreadyLocatedDevice) {
alreadyLocatedDevice = true;
Location loc = new Location();
loc.setLng(Double.toString(location.getLongitude()));
loc.setLat(Double.toString(location.getLatitude()));
((AppDelegate) getApplicationContext()).setSelectedLocation(loc);
Intent findKioskLocation = new Intent(LocationLookup.this, FindKioskLocation.class);
this.dialog.dismiss();
startActivity(findKioskLocation);
}
}
#Override
public void onStatusChanged(String s, int i, Bundle bundle) {
//To change body of implemented methods use File | Settings | File Templates.
}
#Override
public void onProviderEnabled(String s) {
//To change body of implemented methods use File | Settings | File Templates.
}
}
And finally I've added both the ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION permissions in my manifest file.
Any help would be much appreciated!

Here is a nice implementation that I recnetly looked at. Basically by default it uses GPS to get a location. If no location can be found within a certain time period or no satellites are available it switches to Network.
Hope this helps

A Stacktrace from the logcat would have helped you and other developers here understand where the problem is coming from. Try to ask the users to recreate the problem if possible and find out when it is occurring.
As for guidance with the locaton manager, Google Developers just posted a blog recently and also updated the docs on how to use location manager. Check the documentation here and also the blog post which explains it with an example. That might help you better. The blog post also explains how to use different location providers and how to be user friendly and guidance necessary in most ases when using location in Android applications.

For anyone who might follow this thread -I found a mixture of my own approach (admittedly hackish in this code example) and the one mentioned by #bear to work without any issues (plus the location lookup was fast/accurate and error free)
I found the example listed by #bear to be a little more complex than I needed. For starters I wanted to kick off the GPS lookup when a button was clicked and have a simple async task wrapping this so it would throw up a dialog/etc
Next I wanted the exact latitude and longitude (no need to pass this off to another class because my example was simply to use the lat + lng to locate a resource and plot it)
So if you can follow my untested rather copy/paste approach here goes...
Inside your activity you would spin up the service during an onclick lets say ...
LocationManager networkManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
LocationManager gpsManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
LocationService locationProcessor = new LocationService(YourActivityName.this, networkManager, gpsManager, dialog);
locationProcessor.onStartCommand();
Now the location service itself
package com.epicsoftware.android.global;
import android.app.ProgressDialog;
import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.Handler;
import com.epicsoftware.android.activity.LocationLookup;
public class LocationService {
private LocationManager networkLm;
private LocationManager gpsLm;
private LocationListener networkListener;
private LocationListener gpsListener;
private boolean isRunning;
private boolean networkLocDisabled;
private boolean gpsLocDisabled;
private Context activity;
private LocationManager tmpNetworkManager;
private LocationManager tmpGpsManager;
private Handler locationHandler;
private ProgressDialog dialog;
private boolean gpsUpdated;
private boolean done;
public LocationService(final Context activity, LocationManager networkManager, LocationManager gpsManager, ProgressDialog dialog) {
this.tmpNetworkManager = networkManager;
this.tmpGpsManager = gpsManager;
this.activity = activity;
this.dialog = dialog;
}
public void onStartCommand() {
if (!isRunning) {
isRunning = true;
startLocationListeners();
locationHandler = new Handler();
getLocationByZip.start();
}
}
private void startLocationListeners() {
networkListener = new NetworkLocationListener();
gpsListener = new GpsLocationListener();
networkLm = tmpNetworkManager;
gpsLm = tmpGpsManager;
networkLm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, networkListener);
gpsLm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, gpsListener);
}
private Thread getLocationByZip = new Thread() {
public void run() {
try {
for (int i = 0; i < 15;) {
if (!locationDisabled() || !gpsUpdated) {
try {
Thread.sleep(1000);
} catch (Exception e) {
break;
}
i++;
} else {
break;
}
}
locationHandler.post(monitorTheNetworkAndGpsProviders);
} catch (Exception e) {
killService();
done = true;
}
}
};
private Runnable monitorTheNetworkAndGpsProviders = new Runnable() {
#Override
public void run() {
killService();
dialog.dismiss();
if (!done) {
done = true;
((LocationLookup) activity).warnUserThatLocationServicesAreDisabledOrFailed();
}
}
};
private boolean locationDisabled() {
if (gpsLocDisabled && networkLocDisabled) {
done = true;
((LocationLookup) activity).warnUserThatLocationServicesAreDisabledOrFailed();
return true;
} else {
return false;
}
}
private void updateDb(Double lat, Double lon) {
done = true;
((LocationLookup) activity).setLocationDataAndSpinUpNextActivity(lat, lon);
}
public void killService() {
networkLm.removeUpdates(networkListener);
gpsLm.removeUpdates(gpsListener);
}
public class NetworkLocationListener implements LocationListener {
#Override
public void onLocationChanged(Location location) {
if (location != null) {
updateDb(location.getLatitude(), location.getLongitude());
}
}
#Override
public void onProviderDisabled(String provider) {
networkLocDisabled = true;
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
}
public class GpsLocationListener implements LocationListener {
#Override
public void onLocationChanged(Location location) {
if (location != null) {
gpsUpdated = true;
updateDb(location.getLatitude(), location.getLongitude());
}
}
#Override
public void onProviderDisabled(String provider) {
gpsLocDisabled = true;
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
}
}

Getting an updated location throughout my app

I need to have an updated location throughout my app. I'm trying to do so by adding the code shown below in all my activities. My problem is that I can't be sure the user will stay in one activity long enough to get the update. How can I have some application-wise listener to achieve an updated position every given time (say 30min)?
private LocationManager mLocationManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
// My activity stuff
}
private Location getBestLocation(LocationManager locationManager) {
Location location_gps = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
Location location_network = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
// If both are available, get the most recent
if(location_gps!=null && location_network !=null) {
return (location_gps.getTime() > location_network.getTime())?location_gps:location_network;
}
else if(location_gps==null && location_network ==null){
return null;
}
else
return (location_gps==null)?location_network:location_gps;
}
#Override
protected void onResume() {
super.onResume();
// Request location updates at startup
mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, LOCATION_UPDATE_MIN_TIME, LOCATION_UPDATE_MIN_DIST, this);
mLocationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, LOCATION_UPDATE_MIN_TIME, LOCATION_UPDATE_MIN_DIST, this);
getBestLocation(mLocationManager)
}
#Override
protected void onPause() {
super.onPause();
// Remove the locationlistener updates when Activity is paused
mLocationManager.removeUpdates(this);
}
#Override
public void onLocationChanged(Location location) {
GlobalVars.lat = (Double) (location.getLatitude());
GlobalVars.lng = (Double) (location.getLongitude());
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// Nothing here
}
#Override
public void onProviderEnabled(String provider) {
Location location = getBestLocation(mLocationManager);
// Initialize the location fields
if (location != null) {
GlobalVars.lat = (Double) (location.getLatitude());
GlobalVars.lng = (Double) (location.getLongitude());
}
}
#Override
public void onProviderDisabled(String provider) {
}

After further investigation, I ended up using a service.
public class LocationService extends Service implements LocationListener {
LocationManager locationManager;
#Override
public IBinder onBind(Intent intent) {
return null;
}
#Override
public void onCreate() {
locationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
Location loc = getBestLocation(locationManager);
GlobalVars.lat = (Double) (loc.getLatitude());
GlobalVars.lng = (Double) (loc.getLongitude());
}
public void onLocationChanged(Location loc) {
GlobalVars.lat = (Double) (loc.getLatitude());
GlobalVars.lng = (Double) (loc.getLongitude());
}
public static Location getBestLocation(LocationManager locationManager) {
Location location_gps = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
Location location_network = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
// If both are available, get the most recent
if(location_gps!=null && location_network !=null) {
return (location_gps.getTime() > location_network.getTime())?location_gps:location_network;
}
else if(location_gps==null && location_network ==null){
return null;
}
else
return (location_gps==null)?location_network:location_gps;
}
public void onProviderEnabled(String s){}
public void onProviderDisabled(String s){}
public void onStatusChanged(String s, int i, Bundle b){}
#Override
public void onDestroy() {
locationManager.removeUpdates(this);
}
}

Every Android application has one Application (or subclass) in it, and you can ovverride the default to provide your own application-wide functionality. Simply subclass android.app.Application to add your additional functionality, and declare your Application in your manifest. In the manifest's <application> node, provide an android:name attribute equal to the full name of your override.
Once you've got that, giving it a static set of access methods is trivial.

Android: Nothing past onCreate is happening

I got this class, and nothing inside the onCreate is happening? Does it not automatically get called upon initialization?
Code is below, Thanks alot! - Micheal
package com.michealbach.livedrops;
import java.io.IOException;
import java.util.List;
import java.util.Locale;
import android.app.Activity;
public class AnyClass extends Activity {
double latitude = 0;
double longitude = 0;
String addressString = "Address Initialized";
String postalString = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
postalString = "Why doesn't this String change happen at all?";
}
public double getLongitude() {
return longitude;
}
public double getLatitude() {
return latitude;
}
public String getAddress() {
return addressString;
}
public String getPostal() {
return postalString;
}
}
Doing this results in a "application has stopped unexpectedly. Please try again". If I initialize the string to some set of characters instead of null, it'll just stay that way. Should it not do what is inside the onCreate() and make that change?

onLocationChanged() is just a class method in your program, it's not conected to anything. You have to do
private final LocationListener locationListener = new LocationListener() {
#Override
public void onLocationChanged(Location location) {
// Do stuff
}
#Override
public void onProviderDisabled(String provider) {
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
};
And then in your onCreate()
LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
cr = new Criteria();
cr.setPowerRequirement(Criteria.POWER_LOW);
cr.setAccuracy(Criteria.ACCURACY_FINE);
provider = lm.getBestProvider(cr,true);
lm.requestLocationUpdates(provider, minTIME, minDISTANCE, locationListener );