GPS Location in Android Devices

In order to get started with the location capabilities of the Android API, the first step is to take reference of the LocationManager class, which provides access to the system location services. This is done via the getSystemService of our activity (actually it inherits it from the Context parent class). Then, we request updates of the device's location using the methodrequestLocationUpdates. In that method, we provide the name of the preferred location provider (in our case GPS), the minimum time interval for notifications (in milliseconds), the minimum distance interval for notifications (in meters) and finally a class implementing the LocationListener interface. That interface declares methods for handling changes in the user's location as well as changes in the location provider's status. All the above can be translated into code as below:

package com.example.android.lbs;

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 GPSActivity extends Activity {
    
    private static final long MINIMUM_DISTANCE_CHANGE_FOR_UPDATES = 1; // in Meters
    private static final long MINIMUM_TIME_BETWEEN_UPDATES = 1000; // in Milliseconds
    
    protected LocationManager locationManager;
    
    protected Button retrieveLocationButton;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        retrieveLocationButton = new Button(this);
 retrieveLocationButton.setText("GPS");
 addContentView(retrieveLocationButton, new LayoutParams(android.view.ViewGroup.LayoutParams.WRAP_CONTENT ,                             android.view.ViewGroup.LayoutParams.FILL_PARENT));

        
        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() {
            @Override
            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(LbsGeocodingActivity.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(LbsGeocodingActivity.this, message, Toast.LENGTH_LONG).show();
        }

        public void onStatusChanged(String s, int i, Bundle b) {
            Toast.makeText(LbsGeocodingActivity.this, "Provider status changed",
                    Toast.LENGTH_LONG).show();
        }

        public void onProviderDisabled(String s) {
            Toast.makeText(LbsGeocodingActivity.this,
                    "Provider disabled by the user. GPS turned off",
                    Toast.LENGTH_LONG).show();
        }

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

    }
    
}

In order to be able to run the above code, the necessary permissions have to be granted. These are:
1. ACCESS_FINE_LOCATION
2. ACCESS_MOCK_LOCATION
3. ACCESS_COARSE_LOCATION
Include those in the AndroidManifest.xml file, which will be as follows:

 <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" />

Read more: http://www.javacodegeeks.com/2010/09/android-location-based-services.html