import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(final String url) {

        // Making HTTP request
        try {
            // Construct the client and the HTTP request.
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            // Execute the POST request and store the response locally.
            HttpResponse httpResponse = httpClient.execute(httpPost);
            // Extract data from the response.
            HttpEntity httpEntity = httpResponse.getEntity();
            // Open an inputStream with the data content.
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            // Create a BufferedReader to parse through the inputStream.
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            // Declare a string builder to help with the parsing.
            StringBuilder sb = new StringBuilder();
            // Declare a string to store the JSON object data in string form.
            String line = null;

            // Build the string until null.
            while ((line = reader.readLine()) != null) {
                sb.append(line + "n");
            }

            // Close the input stream.
            is.close();
            // Convert the string builder data to an actual string.
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // Try to parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // Return the JSON Object.
        return jObj;

    }


    public JSONObject makeHttpRequest(String url, String method,
                                      List params) {

        // Haciendo la Petición HTTP
        try {

            // check for request method
            if(method == "POST"){
                // request method is POST
                // defaultHttpClient
                DefaultHttpClient httpClient = new DefaultHttpClient();
                HttpPost httpPost = new HttpPost(url);
                httpPost.setEntity(new UrlEncodedFormEntity(params));

                HttpResponse httpResponse = httpClient.execute(httpPost);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();

            }else if(method == "GET"){
                // request method is GET
                DefaultHttpClient httpClient = new DefaultHttpClient();
                String paramString = URLEncodedUtils.format(params, "utf-8");
                url += "?" + paramString;
                HttpGet httpGet = new HttpGet(url);

                HttpResponse httpResponse = httpClient.execute(httpGet);
                HttpEntity httpEntity = httpResponse.getEntity();
                is = httpEntity.getContent();
            }

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

package com.org.hewerth.happypets;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.AsyncTask;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class LoginActivity extends Activity implements OnClickListener {

    private EditText user, pass;
    private Button mSubmit, mRegister;

    private ProgressDialog pDialog;

    // Clase JSONParser
    JSONParser jsonParser = new JSONParser();


    // si trabajan de manera local "localhost" :
    // En windows tienen que ir, run CMD > ipconfig
    // buscar su IP
    // y poner de la siguiente manera
    // "http://xxx.xxx.x.x:1234/cas/login.php";

    private static final String LOGIN_URL = "http://login.php";

    // La respuesta del JSON es
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_MESSAGE = "message";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        // setup input fields
        user = (EditText) findViewById(R.id.usuNick);
        pass = (EditText) findViewById(R.id.usuPass);

        // setup buttons
        mSubmit = (Button) findViewById(R.id.login);
        mRegister = (Button) findViewById(R.id.register);

        // register listeners
        mSubmit.setOnClickListener(this);
        mRegister.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch (v.getId()) {
            case R.id.login:
                new AttemptLogin().execute();
                break;
            case R.id.register:
                Intent i = new Intent(this, RegistroActivity.class);
                startActivity(i);
                break;

            default:
                break;
        }
    }

    class AttemptLogin extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(LoginActivity.this);
            pDialog.setMessage("Attempting login...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

        String username = user.getText().toString();
        String password = pass.getText().toString();

        @Override
        protected String doInBackground(String... args) {
            int success;

            try {
                // Building Parameters
                List params = new ArrayList();
                params.add(new BasicNameValuePair("alias", username));
                params.add(new BasicNameValuePair("password", password));

                Log.d("request!", "starting");
                // getting product details by making HTTP request
                JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST",
                        params);

                // check your log for json response
                Log.d("Login attempt", json.toString());

                // json success tag
                success = json.getInt(TAG_SUCCESS);
                if (success == 1) {
                    Log.d("Login Successful!", json.toString());
                    // save user data
                    SharedPreferences sp = PreferenceManager
                            .getDefaultSharedPreferences(LoginActivity.this);
                    Editor edit = sp.edit();
                    edit.putString("username", username);
                    edit.commit();

                    Intent i = new Intent(LoginActivity.this, ReadComments.class);
                    finish();
                    startActivity(i);
                    return json.getString(TAG_MESSAGE);
                } else {
                    Log.d("Login Failure!", json.getString(TAG_MESSAGE));
                    return json.getString(TAG_MESSAGE);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;

        }

        protected void onPostExecute(String file_url) {
            // dismiss the dialog once product deleted
            pDialog.dismiss();
            if (file_url != null) {
                Toast.makeText(LoginActivity.this, file_url, Toast.LENGTH_LONG).show();
            }
        }
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="@drawable/fondo"
    android:orientation="vertical"
    android:padding="20dip"
    android:weightSum="1">

    <TextView
        android:id="@+id/link_to_register"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="40dip"
        android:layout_marginTop="40dip"
        android:fontFamily="cursive"
        android:gravity="center"
        android:text="HappyPets"
        android:textColor="@android:color/black"
        android:textSize="60sp" />

    <EditText
        android:id="@+id/usuNick"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="Nombre de Usuario"
        android:name="username_textview"
        android:inputType="text"
        android:textAlignment="center" />

    <EditText
        android:id="@+id/usuPass"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="30dip"
        android:layout_marginTop="15dip"
        android:hint="Contraseña"
        android:name="password_textview"
        android:inputType="textPassword"
        android:textAlignment="center" />


    <Button
        android:id="@+id/login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:backgroundTint="@color/colorPrimary"
        android:elevation="0dp"
        android:paddingLeft="15dip"
        android:paddingRight="15dip"
        android:text="Ingresar"
        android:name="submit"
        android:textColor="@android:color/background_light" />

    <Button
        android:id="@+id/register"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:backgroundTint="@color/colorPrimary"
        android:elevation="0dp"
        android:paddingLeft="15dip"
        android:paddingRight="15dip"
        android:text="Registrate"
        android:textAlignment="center"
        android:textColor="@android:color/background_light" />

</LinearLayout>

<ProgressBar
     android:id="@+id/progbar"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     style="@android:style/Widget.ProgressBar.Small"
     android:layout_marginRight="5dp" />

int mStatus;
//...
ProgressBar mProgress = (ProgressBar) findViewById(R.id.progbar);
mProgress.setProgress(mStatus); // actualizar status
// o relativamente
mProgress.incrementProgressBy(1);

@Override
protected void onPause() {
    if(pDialog != null){
        pDialog.dismiss();
    }
    super.onPause();
}

private static boolean foreground = true; //valida si se permite mostrar el Dialog.


    @Override
    protected void onPause() {
        foreground = false;
      super.onPause();
    }

    @Override
    protected void onResume() {
        foreground = true;
      super.onResume();
    }

@Override
    protected void onPreExecute() {
        super.onPreExecute();
        if (foreground){ //Valida si será mostrado el Dialogo.

          pDialog = new ProgressDialog(LoginActivity.this);
          pDialog.setMessage("Attempting login...");
          pDialog.setIndeterminate(false);
          pDialog.setCancelable(true);
          pDialog.show();

        }
    }