Android Open Source - android_retrieval_system A R S Location Listener

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License

The source code is released under:

GNU General Public License

Java Source Code

/*
 * This file is part of Android retrieval system project.
 * //from  w ww  . j av a2  s  . com
 * Android retrieval system is free software: you can redistribute it
 * and/or modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the License,
 * or (at your option) any later version. 
 * 
 * Android retrieval system is distributed in the hope that
 * it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with Android retrieval system. If not, see <http://www.gnu.org/licenses/>.
 */

package net.deerhunter.ars.location;

import android.location.Location;
import android.location.LocationListener;
import android.os.Bundle;

/**
 * Used to listen the location update.
 * 
 * @author DeerHunter (vityokkv73@gmail.com)
 */
public class ARSLocationListener implements LocationListener {

  private static volatile ARSLocationListener instance;

  private Location bestLocation = null;

  private ARSLocationListener() {
  }

  /**
   * Returns the instance of the <code>ARSLocationListener</code> class.
   * 
   * @return The instance of the <code>ARSLocationListener</code> class
   */
  public static ARSLocationListener getInstance() {
    ARSLocationListener localInstance = instance;
    if (localInstance == null) {
      synchronized (ARSLocationListener.class) {
        localInstance = instance;
        if (localInstance == null) {
          instance = localInstance = new ARSLocationListener();
        }
      }
    }
    return localInstance;
  }

  // 3 minutes
  public static final int START_LOCATION_LISTENING_TIME = 3 * 60;
  // 1 hour
  public static final int LOCATION_LISTENING_INTERVAL = 60 * 60;
  // 3 minutes
  public static final int UPDATE_PERIOD = 3 * 60;

  @Override
  public void onLocationChanged(Location location) {
    if (isBetterLocation(location, bestLocation))
      bestLocation = location;
  }

  @Override
  public void onProviderDisabled(String provider) {
  }

  @Override
  public void onProviderEnabled(String provider) {
  }

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

  /**
   * 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
   */
  private 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 > UPDATE_PERIOD;
    boolean isSignificantlyOlder = timeDelta < -UPDATE_PERIOD;
    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
   * 
   * @param provider1 First provider
   * @param provider2 Second provider
   * @return Flags that indicates that providers used the same module
   */
  private boolean isSameProvider(String provider1, String provider2) {
    if (provider1 == null) {
      return provider2 == null;
    }
    return provider1.equals(provider2);
  }

  /**
   * Returns the location with the best accuracy.
   * 
   * @return Location with the best accuracy
   */
  public Location getBestLocation() {
    return bestLocation;
  }
}

Java Source Code List

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