<?php

 define('DB_NAME','android' );
 define('DB_USER','root');
 define('DB_PASSWORD','' );
 define('DB_HOST','localhost' );


 ?>

<?php

    class Dbconnect{

        private $con;

        function __construct(){

        }

        function connect(){
            include_once dirname(__FILE__).'/constant.php';
            $this->con = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

            if(mysqli_connect_errno()){
                echo "Failed to connect with database".mysqli_connect_err();
            }

            return $this->con;
        }
    }

<?php

class DbOperations{

        private $con;

        function __construct(){

            require_once dirname(__FILE__).'/Dbconnect.php';

            $db = new Dbconnect();

            $this->con = $db->connect();

        }

        /*CRUD -> C -> CREATE */

        public function createUser($username, $pass, $email){
            if($this->isUserExist($username,$email)){
                return 0;
            }else{
                $password = md5($pass);
                $stmt = $this->con->prepare("INSERT INTO `users` (`id`, `username`, `password`, `email`) VALUES (NULL, ?, ?, ?);");
                $stmt->bind_param("sss",$username,$password,$email);

                if($stmt->execute()){
                    return 1;
                }else{
                    return 2;
                }
            }

        }

        public function userLogin($username, $pass){
            $password = md5($pass);
            $stmt = $this->con->prepare("SELECT id FROM users WHERE username = ?
             AND password = ?");
            $stmt->bind_param("ss",$username,$password);
            $stmt->execute();
            $stmt->store_result();
            return $stmt->num_rows > 0;
        }

        public function getUserByUsername($username){
            $stmt = $this->con->prepare("SELECT * FROM users WHERE username = ?");
            $stmt->bind_param("s",$username);
            $stmt->execute();
            return $stmt->get_result()->fetch_assoc();
        }


        private function isUserExist($username, $email){
            $stmt = $this->con->prepare("SELECT id FROM users WHERE username = ? OR email = ?");
            $stmt->bind_param("ss", $username, $email);
            $stmt->execute();
            $stmt->store_result();
            return $stmt->num_rows > 0;
        }

}
?>

<?php

require_once '../includes/DbOperations.php';

$response = array();

if($_SERVER['REQUEST_METHOD']=='POST'){
    if(
        isset($_POST['username']) and
            isset($_POST['email']) and
                isset($_POST['password']))
        {
        //operate the data further

        $db = new DbOperations();

        $result = $db->createUser(   $_POST['username'],
                                    $_POST['password'],
                                    $_POST['email']
                                );
        if($result == 1){
            $response['error'] = false;
            $response['message'] = "User registered successfully";
        }elseif($result == 2){
            $response['error'] = true;
            $response['message'] = "Some error occurred please try again";
        }elseif($result == 0){
            $response['error'] = true;
            $response['message'] = "It seems you are already registered, please choose a different email and username";
        }

    }else{
        $response['error'] = true;
        $response['message'] = "Required fields are missing";
    }
}else{
    $response['error'] = true;
    $response['message'] = "Invalid Request";
}

echo json_encode($response);

<?php

require_once '../includes/DbOperations.php';

$response = array();

if($_SERVER['REQUEST_METHOD']=='POST'){
    if(isset($_POST['username']) and isset($_POST['password'])){
        $db = new DbOperations();

        if($db->userLogin($_POST['username'], $_POST['password'])){
            $user = $db->getUserByUsername($_POST['username']);
            $response['error'] = false;
            $response['id'] = $user['id'];
            $response['email'] = $user['email'];
            $response['username'] = $user['username'];
        }else{
            $response['error'] = true;
            $response['message'] = "Invalid username or password";
        }

    }else{
        $response['error'] = true;
        $response['message'] = "Required fields are missing";
    }
}

echo json_encode($response);

package com.example.ahmad.volli;

import android.app.ProgressDialog;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;

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

import java.util.HashMap;
import java.util.Map;

import static android.R.id.progress;
import static com.example.ahmad.volli.R.id.textViewLogin;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText editTextUsername, editTextEmail, editTextPassword;
    private Button buttonRegister;
    private ProgressDialog progressDialog;
    private TextView textViewLogin;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if(SharedPrefManager.getInstance(this).isLoggedIn()){
            finish();
            startActivity(new Intent(this, ProfileActivity.class));
            return;
        }

        editTextEmail = (EditText) findViewById(R.id.editTextEmail);
        editTextUsername = (EditText) findViewById(R.id.editTextUsername);
        editTextPassword = (EditText) findViewById(R.id.editTextPassword);
        textViewLogin = (TextView) findViewById(R.id.textViewLogin);

        buttonRegister = (Button) findViewById(R.id.buttonRegister);
        progressDialog = new ProgressDialog(this);
        textViewLogin.setOnClickListener(this);
        buttonRegister.setOnClickListener(this);

    }
    private void registerUser(){
        final String email = editTextEmail.getText().toString().trim() ;
        final String username = editTextUsername.getText().toString().trim();
        final String password = editTextPassword.getText().toString().trim();
        progressDialog.setMessage("Plz Wait");
        progressDialog.show();

        StringRequest stringRequest = new StringRequest(Request.Method.POST, Constants.URL_REGISTER,
                new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                progressDialog.dismiss();

                try {
                    JSONObject jsonObject = new JSONObject(response);
                    Toast.makeText(getApplicationContext(),jsonObject.getString("message"),Toast.LENGTH_SHORT).show();
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        },
        new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
progressDialog.hide();
                Toast.makeText(getApplicationContext(),error.getMessage(),Toast.LENGTH_LONG).show();
            }
        })
        {
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String,String> params = new HashMap<>();
                params.put("username" ,username);
                params.put("email" ,email);
                params.put("password" ,password);
                return params;


            }
        };

       RequestHandler.getInstance(this).addToRequestQueue(stringRequest);

    }

    @Override
    public void onClick(View view) {
        if (view == buttonRegister)
            registerUser();
        if (view == textViewLogin)
        {
            startActivity(new Intent(this,LoginActivity.class));
        }

    }
}

/**
 * Created by ahMad on 4/22/2018.
 */

public class Constants {

    public static final String ROOT_URL = "http://172.21.34.7/Android/v1/";

    public static final String  URL_REGISTER = ROOT_URL+"registerUser.php";
    public static final String  URL_LOGIN = ROOT_URL+"userLogin.php";

package com.example.ahmad.volli;

import android.app.ProgressDialog;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.android.volley.AuthFailureError;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;

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

import java.util.HashMap;
import java.util.Map;

public class LoginActivity extends AppCompatActivity implements View.OnClickListener  {

    private EditText editTextUsername, editTextPassword;
    private Button buttonLogin;
    private ProgressDialog progressDialog;

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

        if(SharedPrefManager.getInstance(this).isLoggedIn()){
            finish();
            startActivity(new Intent(this, ProfileActivity.class));
            return;
        }

        editTextUsername = (EditText) findViewById(R.id.editTextUsername);
        editTextPassword = (EditText) findViewById(R.id.editTextPassword);
        buttonLogin = (Button) findViewById(R.id.buttonLogin);

        progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Please wait...");
        buttonLogin.setOnClickListener(this);

    }

    private void userLogin() {
        final String username = editTextUsername.getText().toString().trim();
        final String password = editTextPassword.getText().toString().trim();

        progressDialog.show();

        StringRequest stringRequest = new StringRequest(
                Request.Method.POST,
                Constants.URL_LOGIN,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        progressDialog.dismiss();
                        try {
                            JSONObject obj = new JSONObject(response);
                            if(!obj.getBoolean("error")){
                                SharedPrefManager.getInstance(getApplicationContext())
                                        .userLogin(
                                                obj.getInt("id"),
                                                obj.getString("username"),
                                                obj.getString("email")
                                        );
                                startActivity(new Intent(getApplicationContext(), ProfileActivity.class));
                                finish();
                            }else{
                                Toast.makeText(
                                        getApplicationContext(),
                                        obj.getString("message"),
                                        Toast.LENGTH_LONG
                                ).show();
                            }
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        progressDialog.dismiss();

                        Toast.makeText(
                                getApplicationContext(),
                                error.getMessage(),
                                Toast.LENGTH_LONG
                        ).show();
                    }
                }
        ){
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String, String> params = new HashMap<>();
                params.put("username", username);
                params.put("password", password);
                return params;
            }

        };
        RequestHandler.getInstance(this).addToRequestQueue(stringRequest);


    }

    @Override
    public void onClick(View view) {
        if(view == buttonLogin){
            userLogin();
        }
    }
    }

package com.example.ahmad.volli;

import android.content.Context;
import android.content.SharedPreferences;

/**
 * Created by Belal on 26/11/16.
 */

public class SharedPrefManager {
    private static SharedPrefManager mInstance;
    private static Context mCtx;

    private static final String SHARED_PREF_NAME = "mysharedpref12";
    private static final String KEY_USERNAME = "username";
    private static final String KEY_USER_EMAIL = "useremail";
    private static final String KEY_USER_ID = "userid";

    private SharedPrefManager(Context context) {
        mCtx = context;

    }

    public static synchronized SharedPrefManager getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new SharedPrefManager(context);
        }
        return mInstance;
    }
    public boolean userLogin(int id, String username, String email){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();

        editor.putInt(KEY_USER_ID, id);
        editor.putString(KEY_USER_EMAIL, email);
        editor.putString(KEY_USERNAME, username);

        editor.apply();

        return true;
    }

    public boolean isLoggedIn(){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        if(sharedPreferences.getString(KEY_USERNAME, null) != null){
            return true;
        }
        return false;
    }

    public boolean logout(){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.clear();
        editor.apply();
        return true;
    }

    }