Determine location gps and wifi

Question

I want to show a dialog while the location of the device is determined. I also want to use both the wifi and gps provider. When the location changes, the latitude and longitude values should be updated. I looked for an example but I didn't find anything.

Answer 1

Here is an example how to define location Manager and get on location change event:

public class LocationChangeListener  implements LocationListener{


private LocationManager mLocationManager = null;
private static final int TWO_MINUTES = 1000 * 60 * 2;
private Location currentBestLocation = null;

public LocationChangeListener(Context context) {
    super(context);
}

public void impl(int refreshPeriod, int accuracyInMeters){



    // Get the location manager
    mLocationManager = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE);

    currentBestLocation = getLastBestLocation();

    boolean enabled = mLocationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);

    // Check if enabled and if not send user to the GSP settings
    // Better solution would be to display a dialog and suggesting to 
    // go to the settings
    if (!enabled) {
        Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
        mContext.startActivity(intent);
    } 


    Criteria criteria = new Criteria();
    //criteria.setAccuracy(Criteria.ACCURACY_FINE);
    //criteria.setCostAllowed(false);

    String provider = mLocationManager.getBestProvider(criteria, false);
    Location location = mLocationManager.getLastKnownLocation(provider);

    LocationListener listener = this;       
    mLocationManager.requestLocationUpdates(provider, refreshPeriod, accuracyInMeters, listener);
    //mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, listener);
    //mLocationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, listener);

    this.onLocationChanged(location);

    // Initialize the location fields
    if (location == null) {
        //Location not available

        mLocationManager.removeUpdates(this);
    }

}

/**
 * This method returns the last know location, between the GPS and the Network one.
 * For this method newer is best :)
 * 
 * @return the last know best location
 */
private Location getLastBestLocation() {
    Location locationGPS = mLocationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
    Location locationNet = mLocationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);

    long GPSLocationTime = 0;
    if (null != locationGPS) { GPSLocationTime = locationGPS.getTime(); }

    long NetLocationTime = 0;

    if (null != locationNet) {
        NetLocationTime = locationNet.getTime();
    }

    if ( 0 < GPSLocationTime - NetLocationTime ) {
        return locationGPS;
    }
    else{
        return locationNet;
    }

}

/**
 * This method modify the last know good location according to the arguments.
 * 
 * @param location      the possible new location
 */
void makeUseOfNewLocation(Location location) {
    if ( isBetterLocation(location, currentBestLocation) ) {
        currentBestLocation = location;
    }
}

public void onLocationChanged(Location location) {

    makeUseOfNewLocation(location);

    if(currentBestLocation == null){
        currentBestLocation = location;
    }


    FlowController.isTriggerEventReceived = true;       
    mCobytLocationCallback.onLocationChanged(currentBestLocation);      
}

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

}

public void onProviderEnabled(String provider) {


}

public void onProviderDisabled(String provider) {


}   

/** Determines whether one Location reading is better than the current Location fix
 * @param location  The new Location that you want to evaluate
 * @param currentBestLocation  The current Location fix, to which you want to compare the new one
 */
protected boolean isBetterLocation(Location location, Location currentBestLocation) {
    if (currentBestLocation == null) {
        // A new location is always better than no location
        return true;
    }

    // Check whether the new location fix is newer or older
    long timeDelta = location.getTime() - currentBestLocation.getTime();
    boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
    boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
    boolean isNewer = timeDelta > 0;

    // If it's been more than two minutes since the current location, use the new location
    // because the user has likely moved
    if (isSignificantlyNewer) {
        return true;
        // If the new location is more than two minutes older, it must be worse
    } else if (isSignificantlyOlder) {
        return false;
    }

    // Check whether the new location fix is more or less accurate
    int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
    boolean isLessAccurate = accuracyDelta > 0;
    boolean isMoreAccurate = accuracyDelta < 0;
    boolean isSignificantlyLessAccurate = accuracyDelta > 200;

    // Check if the old and new location are from the same provider
    boolean isFromSameProvider = isSameProvider(location.getProvider(),
            currentBestLocation.getProvider());

    // Determine location quality using a combination of timeliness and accuracy
    if (isMoreAccurate) {
        return true;
    } else if (isNewer && !isLessAccurate) {
        return true;
    } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
        return true;
    }
    return false;
}

/** Checks whether two providers are the same */
private boolean isSameProvider(String provider1, String provider2) {
    if (provider1 == null) {
        return provider2 == null;
    }
    return provider1.equals(provider2);
}



public void destroyManager() {

    if(mLocationManager != null){
        mLocationManager.removeUpdates(this);

        mLocationManager = null;
    }       
}
}

Since Android has

GPS_PROVIDER and NETWORK_PROVIDER you can register to both and start fetch events from onLocationChanged(Location location) from 2 at the same time. So far so good. Now the question do we need 2 results or we should take the best. As I know NETWORK PROVIDER results have better accuracy than GPS.

Before we start listen on Location change we will implement followed method private Location getLastBestLocation(). This method returns the last know location, between the GPS and the Network one. For this method newer is best.