TrafficLightSpotterUserLocationUtils.java

package <your package>;

import java.util.ArrayList;

import org.json.JSONException;
import org.json.JSONObject;

import za.co.smartcitizens.trafficlights.spotter.models.LastKnownUserPosition;
import za.co.smartcitizens.trafficlights.spotter.models.TrafficLightIntersectionGeofence;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.location.Location;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;

/**
 * This utility class is used to provide functionality to detect distance movement for the user so as to automatically refresh the geofences
 * closest to the user. This provides a fairly good example of how to use LocationListener in a utility class (not an Activity). 
 * @author Ishmael Makitla
           http://ishLema.co.za 
 *
 */
public class TrafficLightSpotterUserLocationUtils implements LocationListener{

	 private static final String TAG = TrafficLightSpotterUserLocationUtils.class.getSimpleName();
	 private static final String SHARED_PREFERENCES_LAST_LOCATION_KEY = "lastLocation";
	 private static final int SIGNIFICANT_DISPLACEMENT_THRESHOLD = 5; //5 km distance
	 private Context context;
	  private GoogleApiClient googleApiClient;
	  private Gson gson;
	  private SharedPreferences prefs;
	  private GeofenceRefreshRequestListener geofenceRefreshRequestListener;
	  
	  private static TrafficLightSpotterUserLocationUtils INSTANCE;
	  public static TrafficLightSpotterUserLocationUtils getInstance(){
			if(INSTANCE == null){ INSTANCE = new TrafficLightSpotterUserLocationUtils(); }
			return INSTANCE;
	  }
	  
	  public void init(Context ctx, GoogleApiClient connectedGoogleAPIClient, GeofenceRefreshRequestListener refreshRequestListener){
		  this.context = ctx;
		  this.googleApiClient = connectedGoogleAPIClient;
		  this.geofenceRefreshRequestListener = refreshRequestListener;
		  prefs = PreferenceManager.getDefaultSharedPreferences(context);
		  requestLocationUpdates();
	  }
	  
	  /**
		* Helper method to connect the Google API Client
	   */
	 private void requestLocationUpdates() {
		 Log.i(TAG,"requestLocationUpdates"); 
		try{
			LocationRequest locationRequest = LocationRequest.create();
			locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
			locationRequest.setInterval(180000); // update every (3) minutes 
			LocationServices.FusedLocationApi.requestLocationUpdates(googleApiClient, locationRequest, this);			
		}
		catch(Exception e){
			Log.e(TAG, "Error at requestLocationUpdates. ", e);
		}
	 }
		
			  
	@Override
	public void onLocationChanged(Location location) {
		if(location == null){ return; }
		Log.i(TAG, "onLocationChanged. Lat "+location.getLatitude()+" , Lon: "+location.getLongitude());
		//retrieve last-known location (if it does not exist, then this is the first time we get location updates		
		 processLocationChange(location);
	}
    /**
     * This method measures the distance between the last known location of the user and the current on.
     * It does this to calculate how far the user has moved so that it can update the geofences it setups.
     * 
     * @param currentLocation - the most recent user location 
     */
 	private void processLocationChange(Location currentLocation){
 		if(currentLocation == null){return;}
 		
 		LastKnownUserPosition userPreviousPosition = getLastKnownUserLocation();
 		if(userPreviousPosition == null){
 			//Cannot compare, set this as current location
 			setNewUserPosition(currentLocation);
 			return;
 		}
 		float[] results = new float[3];
				
		Location.distanceBetween(currentLocation.getLatitude(), currentLocation.getLongitude(), userPreviousPosition.getLatitude(), userPreviousPosition.getLongitude(), results);
		float distance = (results.length > 0 ? results[0]: 0);
		if( (distance/1000) >= SIGNIFICANT_DISPLACEMENT_THRESHOLD){
			//the user has moved quite a distance		
			Log.i(TAG, "User has moved "+(distance/1000)+"km. It Is Necessary To Refreshe Geofences.");
			//set as new location
			setNewUserPosition(currentLocation);
									
			//notify the listener
			if(geofenceRefreshRequestListener != null){ geofenceRefreshRequestListener.onGeofenceRefreshRequired(currentLocation); }
		}	
		else{
			Log.i(TAG, "Distance "+(distance/1000)+"km Too Small To Refreshe Geofence. Ignore");
		}
	}
 	
 	/**
 	 * 
 	 * @return
 	 */
 	private LastKnownUserPosition getLastKnownUserLocation(){
 		LastKnownUserPosition lastKnownLocation = null;
 		try{
			String lastPositionString = prefs.getString(SHARED_PREFERENCES_LAST_LOCATION_KEY, null);
			if(lastPositionString !=null && !lastPositionString.trim().isEmpty()){
				lastKnownLocation = LastKnownUserPosition.asLastKnownUserPosition(lastPositionString);
			}
		}
		catch(Exception e){
			Log.e(TAG, "Error at getLastKnownUserLocation. ", e);
		}
 		
 		return lastKnownLocation;
 	}
 	
 	/**
 	 * Record the current location. This is only done when the displacement is above threshold
 	 * @param newLocation
 	 */
 	private void setNewUserPosition(final Location newLocation){
 		LastKnownUserPosition currentPosition = new LastKnownUserPosition(newLocation.getLatitude(), newLocation.getLongitude());
 		
 		try{
 			Editor editor = prefs.edit();
 			editor.putString(SHARED_PREFERENCES_LAST_LOCATION_KEY, currentPosition.toString());
 			editor.apply();
 		}
 		catch(Exception e){
 			Log.e(TAG, "Error at setNewUserPosition. ", e);
 		}
 		 		
		try {
			//do something...in my case I was updating the list of users who should receive alerts;
		} 
		catch (JSONException jse) {
			Log.e(TAG, "Error While Updating Alert Subscription. ", jse);
		}
		catch(Exception e){
			Log.e(TAG, "Error While Updating Alert Subscription. ", e);
		}
 	}
}