nullPointerException en Geocodificador

I am playing around with working with the location but now i keep on getting a nullPointerException when ever i click the button on the app. The button refreshes the location which is displayed. The location is displayed in latitude,longitude, street address,city,country and postal address. here is the code below.

package com.example.metrorails;


import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {
    CurrentPosition currentPosition;
    String address;
    String city;
    String country;
    String postalCode;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button refresh;
        refresh = (Button)findViewById(R.id.refresh);
        refresh.setOnClickListener(new OnClickListener() {

                @Override
            public void onClick(View v) {
                currentPosition = new    CurrentPosition(MainActivity.this);
                TextView showresults = (TextView) findViewById(R.id.show_results);
                showresults.setTextSize(20);

                if(currentPosition.canGetLocation()){

                    double latitude = currentPosition.getLatitude();
                    double longitude = currentPosition.getLongitude();
                    showresults.setText("current latitude: "+latitude +"\n current longitude: "+longitude+ 
                        "\n Address is: " +currentPosition.getAddress() + "\n city is: "+currentPosition.getCity()+
                        "\n Current Country is: "+currentPosition.getCountry() +"\n Area Code : "+currentPosition.getPostalCode());



                }else{
                    // can't get location
                    // GPS or Network is not enabled
                    // Ask user to enable GPS/network in settings
                    currentPosition.showSettingsAlert();    
                }               
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is    present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

I'm still having problems with this program. here is the logcat below.

09-09 18:56:52.393: E/AndroidRuntime(1882): FATAL EXCEPTION: main
09-09 18:56:52.393: E/AndroidRuntime(1882): java.lang.NullPointerException
09-09 18:56:52.393: E/AndroidRuntime(1882):     at   android.content.ContextWrapper.getPackageName(ContextWrapper.java:135)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.location.GeocoderParams.  <init>(GeocoderParams.java:50)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.location.Geocoder.<init>(Geocoder.java:83)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at com.example.metrorails.CurrentPosition.<init>(CurrentPosition.java:71)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at com.example.metrorails.MainActivity$1.onClick(MainActivity.java:31)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.view.View.performClick(View.java:4240)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.view.View$PerformClick.run(View.java:17721)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.os.Handler.handleCallback(Handler.java:730)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.os.Handler.dispatchMessage(Handler.java:92)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.os.Looper.loop(Looper.java:137)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at android.app.ActivityThread.main(ActivityThread.java:5103)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at java.lang.reflect.Method.invokeNative(Native Method)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at java.lang.reflect.Method.invoke(Method.java:525)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-09 18:56:52.393: E/AndroidRuntime(1882):     at dalvik.system.NativeStart.main(Native Method)
09-09 18:57:01.512: I/Process(1882): Sending signal. PID: 1882 SIG: 9

below is the CurrentPosition class.

package com.example.metrorails;

import java.io.IOException;
import java.util.List;
import java.util.Locale;

import android.app.AlertDialog;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
import android.provider.Settings;
import android.util.Log;

public  class CurrentPosition extends Service implements LocationListener {

private final Context mContext;

// flag for GPS status
boolean isGPSEnabled = false;

// flag for network status
boolean isNetworkEnabled = false;

// flag for GPS status
boolean canGetLocation = false;

Location location; // location
double latitude; // latitude
double longitude; // longitude
public static String address;
public static String city;
private static String country;
private static String postalCode;


// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

// Declaring a Location Manager
protected LocationManager locationManager;

public String getAddress(){

    return address;
}
public String getCity(){

        return city;
}
public String getCountry(){

    return country;
}
public String getPostalCode(){

    return postalCode;
}





public CurrentPosition(Context context) {
    this.mContext = context;
    getLocation();
}

public void getLocation() {
    try {
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);

        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
        } else {
            this.canGetLocation = true;
            if (isNetworkEnabled) {
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        MIN_TIME_BW_UPDATES,
                        MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                Log.d("Network", "Network");
                if (locationManager != null) {
                    location = locationManager
                            .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                    if (location != null) {
                        latitude = location.getLatitude();
                        longitude = location.getLongitude();
                    }
                }
            }
            // if GPS Enabled get lat/long using GPS Services
            if (isGPSEnabled) {
                if (location == null) {
                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("GPS Enabled", "GPS Enabled");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                            Geocoder geocode = new Geocoder(this, Locale.getDefault());
                                List<Address> addresses;
                            try {
                                    addresses = geocode.getFromLocation(latitude,longitude, 1);
                                this.address = addresses.get(0).getAddressLine(0);
                                this.city = addresses.get(0).getAddressLine(1);
                                this.country = addresses.get(0).getAddressLine(2);
                                this.postalCode =  addresses.get(0).getPostalCode();
                                } catch (IOException e) {

                                    e.printStackTrace();
                            }
                        }
                    }
                }
            }

    }} catch (Exception e) {
        e.printStackTrace();
    }   

   this.location = location;
}

/**
* Stop using GPS listener
* Calling this function will stop using GPS in your app
* */
public void stopUsingGPS(){
    if(locationManager != null){
        locationManager.removeUpdates(CurrentPosition.this);
    }       
}

/**
 * Function to get latitude
 * */
public double getLatitude(){
    if(location != null){
        latitude = location.getLatitude();
    }

    // return latitude
    return latitude;
}

/**
 * Function to get longitude
 * */
public double getLongitude(){
    if(location != null){
        longitude = location.getLongitude();
    }

    // return longitude
    return longitude;
}

/**
 * Function to check GPS/wifi enabled
 * @return boolean
 * */
public boolean canGetLocation() {
    return this.canGetLocation;
}

/**
* Function to show settings alert dialog
* On pressing Settings button will lauch Settings Options
* */
public void showSettingsAlert(){
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

    // Setting Dialog Title
    alertDialog.setTitle("GPS is settings");

    // Setting Dialog Message
    alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

    // On pressing Settings button
    alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog,int which) {
            Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
            mContext.startActivity(intent);
        }
    });

    // on pressing cancel button
    alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
        dialog.cancel();
        }
    });

    // Showing Alert Message
    alertDialog.show();
}

@Override
public void onLocationChanged(Location location) {
}

@Override
public void onProviderDisabled(String provider) {
}

@Override
public void onProviderEnabled(String provider) {
}

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

@Override
public IBinder onBind(Intent arg0) {
    return null;
 }