Android User Location returning 0.0 for latitude and longitude

I have a class object which retrieves the users latitude and longitude. In my UI thread I create the object in the onCreate method that creates the Activity:

userLocation = new UserLocation(this);

Here is the class snippet:

public UserLocation(Context mContext) {
    //Pass parameter to class field:
    this.mContext = mContext;
    //Fetch the user's location:
    fetchUserLocation();
}

public void fetchUserLocation() {
    // Acquire a reference to the system Location Manager:
    LocationManager locationManager = (LocationManager)this.mContext.getSystemService(Context.LOCATION_SERVICE);

    // Define a listener that responds to location updates:
    LocationListener locationListener = new LocationListener() {
    public void onLocationChanged(Location location) {
        //Manage the data recieved:
        makeUseOfLocation(location);
    }

    public void onStatusChanged(String provider, int status, Bundle extras) {}

    public void onProviderEnabled(String provider) {}

    public void onProviderDisabled(String provider) {}


    };

    // Register the listener with the Location Manager to receive location updates:
    locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);
}

private void makeUseOfLocation(Location location) {
    //Split the data of the location object:
    userLatitude = location.getLatitude();                      
    userLongitude = location.getLongitude();                    

}

/**
 * @return userLatitude
 */
public double getLatitude() {
    return userLatitude;
}

/**
 * @return userLongitude
 */
public double getLongitude() {
    return userLongitude;
}

Now back in the main thread, when a button is pressed, the latitude and longitude is collected:

    // GET THE LATITUDE AND LONGITUDE OF THE USER:
    currentLatitude  = userLocation.getLatitude();
    currentLongitude = userLocation.getLongitude();

Now for say I launch the application, if I press that button right away, the values received are 0.0 for both latitude and longitude.

But, if I launch the application and wait 4-5 seconds then press the button, correct values are then received.

Can anyone tell me the cause of this behavior?

I noticed it when I was writing a method that when the user launches the application if a field is null, then collect latitude and longitude. Well this in turn returns the unfavored 0.0 value.

Thanks!