Location Based Services in Android

Location Based Services

•   Android gives our applications access to the location services through the classes in the android.location package.
•  We can utilize GPS and Android’s Network Location Provider to acquire the user location.
•   GPS provider:
•  GPS is most accurate.
•  It works only outdoors.
•  Quickly consumes battery power.
•  Doesn't return the location as quickly as user want.
•  Network Location Provider:
•  Determines the user location using the cell-tower and Wi-Fi signals.
• It works indoors and outdoors.
• Responds faster.
• It uses less battery.
• To obtain the user location we can use both GPS and Network Location Provider or just one.
• Key classes:
• LocationManager.
• LocationProvider.
• LcoationManager provides access to the system location services. This is done through getSystemService.
• Using LocationManager class we can obtain periodic updates of the locations.
• We can request location updates of devices using requestLocationUpdates() method. This method takes four parameters:
•  Provider - The name of the location provider you wish to use.
• minTime - The minimum time interval for notifications, in milliseconds.
•  minDistance - The minimum distance interval for notifications, in meters.
• listener - An object whose onLocationChanged() method will be called for each location update.
•  In order to receive location updates we must request user permissions.
•    NETWORK_PROVIDER – android.permission.ACCESS_COARSE_LOCATION.
• GPS_PROVIDER -  android.permission.ACCESS_FINE_LOCATION.
• The following statement should be added to the AndroidManifest.xml
• < uses-permission android:name=”android.permission.ACCESS_FINE_LOCATION” />
• If we are using both NETWORK_PROVIDER and GPS_PROVIDER, then we need to request only the ACCESS_FINE_LOCATION permission, because it includes permission for both providers.
•   Using DDMS we can simulate location data in several ways through Emulator Controls. They are as follows:
• Manually send individual longitude/latitude coordinates to the device.
• Use a GPX file describing a route for playback to the device.
• Use a KML file describing individual place marks for sequenced playback to the device.
• To send location data through DDMS we must be sure that a device selected in the Devices panel. (Available from Window > Show View > Other > Devices).

Ø  Example:

Main.xml:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:orientation="vertical"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    >

<TextView 

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="@string/hello"

    />

    <Button

       android:id="@+id/retrieve_location_button"

       android:text="Get Location"

       android:layout_width="wrap_content"

       android:layout_height="wrap_content"

       />

</LinearLayout>

GeoCoderActivity.java:

          package com.snigdha.android;

import android.app.Activity;

import android.content.Context;

import android.location.Location;

import android.location.LocationListener;

import android.location.LocationManager;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.Toast;

public class GeoCoderExampleActivity extends Activity {

    /** Called when the activity is first created. */

private static final long MINIMUM_DISTANCE_CHANGE_FOR_UPDATES = 1;

    private static final long MINIMUM_TIME_BETWEEN_UPDATES = 1000;

    protected LocationManager locationManager;

   protected Button retrieveLocationButton;

    public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

       setContentView(R.layout.main);

 retrieveLocationButton = (Button) findViewById(R.id.retrieve_location_button);

 locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

locationManager.requestLocationUpdates( LocationManager.GPS_PROVIDER,                              MINIMUM_TIME_BETWEEN_UPDATES,MINIMUM_DISTANCE_CHANGE_FOR_UPDATES,

                                   new MyLocationListener()   );

   retrieveLocationButton.setOnClickListener(new OnClickListener() {

public void onClick(View v) { showCurrentLocation();

                               }

                       });                              

                       }  

   protected void showCurrentLocation() {

   Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

    if (location != null) {

  String message = String.format( "Current Location \n Longitude: %1$s \n Latitude: %2$s",   location.getLongitude(), location.getLatitude()   );

   Toast.makeText(GeoCoderExampleActivity.this, message,                    Toast.LENGTH_LONG).show();

                  }

              } 

   private class MyLocationListener implements LocationListener {

       public void onLocationChanged(Location location) {

    String message = String.format( "New Location \n Longitude: %1$s \n Latitude: 2$s",   location.getLongitude(), location.getLatitude()       );

 Toast.makeText(GeoCoderExampleActivity.this, message, oast.LENGTH_LONG).show();

                           }

      public void onStatusChanged(String s, int i, Bundle b) {

Toast.makeText(GeoCoderExampleActivity.this, "Provider status changed",

                                       Toast.LENGTH_LONG).show();

                           }

 public void onProviderDisabled(String s) {

Toast.makeText(GeoCoderExampleActivity.this, "Provider disabled by the user. GPS turned off", Toast.LENGTH_LONG).show();

        }

 public void onProviderEnabled(String s) {                        Toast.makeText(GeoCoderExampleActivity.this, "Provider enabled by the user. GPS turned on", Toast.LENGTH_LONG).show();

                           }

}

}

AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

      package="com.snigdha.android"

      android:versionCode="1"

      android:versionName="1.0">

    <uses-sdk android:minSdkVersion="8" />

   

    <uses-permission  android:name="android.permission.INTERNET"/>

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

<uses-permission android:name="android.permission.ACCESS_MOCK_LOCATION" /> <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

 <application android:icon="@drawable/icon" android:label="@string/app_name">

<activity android:name=".GeoCoderExampleActivity"

                  android:label="@string/app_name">

      <intent-filter>

            <action android:name="android.intent.action.MAIN" />

      <category android:name="android.intent.category.LAUNCHER" />

      </intent-filter>

        </activity>

    </application>                                     

</manifest>

Screen Shots:

Figure-1                                                    

Figure - 2

Figure - 4

Figure - 3

                                                                                                                                                

•  Figure-2 displaying the current location data retrieved by the provider.
• Figure-3 and Figure -4 showing a toast messages when the GPS is disabled and enabled by the user.