Create Chat App for Android using GCM Part 1

Hello friends, in this post I will show you How to Create Chat App for Android using PHP, MySQL and GCM. I have already posted about GCM and Push Notifications in my earlier post as these are very important for creating our chat app. So in this post we will create a simple chat room where many users can interact with each other.

This post was very lengthy so I divided it into two parts.

Part 1: This part will cover about creating server side codes and APIs.
Part 2: In this part we will actually build our chat application.

Table of Contents

1 Create Chat App for Android Live Demo
2 Prerequisite to Create Chat App for Android
3 Create Chat App for Android Tutorial

Create Chat App for Android Live Demo

You can also check this video demonstrating the final app that we will make in this tutorial.

You can also get a live demo of the app that we will be building from below. Just download the apk from the link given and install it to your device. But you need two device to check it.

Download APK

If you tested the apk and want to know how to code it then lets move ahead.

Prerequisite to Create Chat App for Android

You should follow the previous Android Push Notification Tutorial using GCM.
You should also follow the REST API tutorial using SLIM Framework.
Other than the above mentioned tutorial we will be using PHP and MySQL you need a local server like wamp or xampp for it.

It is highly recommended that you go through the above mentioned tutorial before moving ahead on this Create Chat App for Android Tutorial. So lets begin.

Create Chat App for Android Tutorial

In this post we will create server side APIs and in the next post we will built the android application. I am using WAMP server. You can also use other server’s basically what is needed is PHP and MySQL. So lets start with creating database.

Creating Database

This is our database model.

So as you can see we have two tables one is users and other is messages. To create the above tables just copy the following SQL to your phpmyadmin.

-- Created by Simplified Coding https://www.simplifiedcoding.net

-- Last modification date: 2016-05-30 15:41:34.537

-- tables

-- Table: messages

CREATE TABLE messages (

id int NOT NULL AUTO_INCREMENT,

message varchar(100) NOT NULL,

users_id int NOT NULL,

sentat timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,

CONSTRAINT messages_pk PRIMARY KEY (id)

);

-- Table: users

CREATE TABLE users (

id int NOT NULL AUTO_INCREMENT,

name varchar(50) NOT NULL,

email varchar(50) NOT NULL,

gcmtoken text NOT NULL,

CONSTRAINT users_pk PRIMARY KEY (id)

);

-- foreign keys

-- Reference: messages_users (table: messages)

ALTER TABLE messages ADD CONSTRAINT messages_users FOREIGN KEY messages_users (users_id)

REFERENCES users (id);

-- End of file.

Now we have our database. Time to code our API.

Creating RESTful API

I am using PHP Storm as I personally feel it is the best IDE. So whatever IDE you are using open it and create a new PHP Project in the WAMP’s root directory (c:/wamp/www). I have created SimplifiedCodingChat.
Now you have to create the following folder structure as shown in the below screenshot.

First download SLIM Framework 2.x and paste it inside your libs folder.
Now inside include folder create 3 php files Config.php, DbConnect.php and DbOperation.php.
First come inside Config.php and write the following code.

<?php

define('DB_USERNAME', 'root');

define('DB_PASSWORD', '');

define('DB_HOST', 'localhost');

define('DB_NAME', 'db_simplifiedcodingchat');

define('USER_CREATED_SUCCESSFULLY', 0);

define('USER_CREATE_FAILED', 1);

define('USER_ALREADY_EXISTED', 2);

define('GOOGLE_API_KEY','YOUR GOOGLE API KEY');

You may need to change the value of the first 4 constants according to your MySQL database. And you also need to put your Google API Key. If you don’t know what is the google api key please go through the Android Push Notification Tutorial using GCM first.
Now inside DbConnect.php write the following code. It is used to connect with the MySQL Database.

<?php

class DbConnect

{

private $conn;

function __construct()

{

}

/**

* Establishing database connection

* @return database connection handler

function connect()

{

require_once 'Config.php';

// Connecting to mysql database

$this->conn = new mysqli(DB_HOST, DB_USERNAME, DB_PASSWORD, DB_NAME);

// Check for database connection error

if (mysqli_connect_errno()) {

echo "Failed to connect to MySQL: " . mysqli_connect_error();

}

// returing connection resource

return $this->conn;

}

In DbOperation.php we will define functions for all the database related operations. Write the following code in DbOperation.php.

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<?php

class DbOperation

{

private $conn;

//Constructor

function __construct()

{

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

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

// opening db connection

$db = new DbConnect();

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

}

//Function to create a new user

public function createUser($name, $email)

{

if (!$this->isUserExists($email)) {

$stmt = $this->conn->prepare("INSERT INTO users(name, email) values(?, ?)");

$stmt->bind_param("ss", $name, $email);

$result = $stmt->execute();

$stmt->close();

if ($result) {

return USER_CREATED_SUCCESSFULLY;

} else {

return USER_CREATE_FAILED;

}

} else {

return USER_ALREADY_EXISTED;

}

//Function to get the user with email

public function getUser($email)

{

$stmt = $this->conn->prepare("SELECT * FROM users WHERE email=?");

$stmt->bind_param("s", $email);

$stmt->execute();

$user = $stmt->get_result()->fetch_assoc();

return $user;

}

//Function to check whether user exist or not

private function isUserExists($email)

{

$stmt = $this->conn->prepare("SELECT id FROM users WHERE email=?");

$stmt->bind_param("s", $email);

$stmt->execute();

$stmt->store_result();

$num_rows = $stmt->num_rows;

$stmt->close();

return $num_rows > 0;

}

//Function to store gcm registration token in database

public function storeGCMToken($id, $token)

{

$stmt = $this->conn->prepare("UPDATE users SET gcmtoken =? WHERE id=?");

$stmt->bind_param("si", $token, $id);

if ($stmt->execute())

return true;

return false;

}

//Function to get the registration token from the database

//The id is of the person who is sending the message

//So we are excluding his registration token as sender doesnt require notification

public function getRegistrationTokens($id){

$stmt = $this->conn->prepare("SELECT gcmtoken FROM users WHERE NOT id = ?;");

$stmt->bind_param("i",$id);

$stmt->execute();

$result = $stmt->get_result();

$tokens = array();

while($row = $result->fetch_assoc()){

array_push($tokens,$row['gcmtoken']);

}

return $tokens;

}

//Function to add message to the database

public function addMessage($id,$message){

$stmt = $this->conn->prepare("INSERT INTO messages (message,users_id) VALUES (?,?)");

$stmt->bind_param("si",$message,$id);

if($stmt->execute())

return true;

return false;

}

//Function to get messages from the database

public function getMessages(){

$stmt = $this->conn->prepare("SELECT a.id, a.message, a.sentat, a.users_id, b.name FROM messages a, users b WHERE a.users_id = b.id ORDER BY a.id ASC;");

$stmt->execute();

$result = $stmt->get_result();

return $result;

}

Inside libs folder create a new folder named gcm and inside it create a new file named gcm.php and write the following code. This file will handle our push notifications.

<?php

class GCM

{

function __construct()

{

}

//This function will send message to the given registration ids

//We are also passing a message that is actually an array containing the message

public function sendMessage($registration_ids, $message) {

$fields = array(

'registration_ids' => $registration_ids,

'data' => $message,

);

//In this function we are calling the main method responsible for sending push notification

//it is sendPushNotification

return $this->sendPushNotification($fields);

}

//This is the main method responsible for sending push notification

//I have already explained it in previous tutorials

private function sendPushNotification($fields){

include_once __DIR__ . '/../../include/Config.php';

$url = 'https://android.googleapis.com/gcm/send';

$headers = array(

'Authorization: key=' . GOOGLE_API_KEY,

'Content-Type: application/json'

);

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, $url);

curl_setopt($ch, CURLOPT_POST, true);

curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);

curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($fields));

$result = curl_exec($ch);

if ($result === FALSE) {

die('Curl failed: ' . curl_error($ch));

}

curl_close($ch);

return $result;

}

Now come inside v1 folder and create a .htaccess file and write the following.

RewriteEngine On

RewriteCond %{REQUEST_FILENAME} !-f

RewriteRule ^(.*)$ %{ENV:BASE}index.php [QSA,L]

Finally in v1 folder create index.php this file will handle all the API calls.

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<?php

require_once '../include/DbOperation.php';

require_once '../libs/gcm/gcm.php';

require '.././libs/Slim/Slim.php';

\Slim\Slim::registerAutoloader();

$app = new \Slim\Slim();

// User id from db - Global Variable

$user_id = NULL;

/**

* User Registration

* url - /register

* method - POST

* params - name, email

$app->post('/register', function () use ($app) {

//Verifying parameters

verifyRequiredParams(array('name', 'email'));

//Response array

$response = array();

//Getting request parameters

$name = $app->request->post('name');

$email = $app->request->post('email');

//Vaidating email

validateEmail($email);

//Creating a db object

$db = new DbOperation();

//INserting user to database

$res = $db->createUser($name, $email);

//If user created

//Adding the user detail to response

if ($res == USER_CREATED_SUCCESSFULLY) {

$response["error"] = false;

$user = $db->getUser($email);

$response['id'] = $user['id'];

$response['name'] = $user['name'];

$response['email'] = $user['email'];

echoResponse(201, $response);

//If user creating failes adding error to response

} else if ($res == USER_CREATE_FAILED) {

$response["error"] = true;

$response["message"] = "Oops! An error occurred while registereing";

echoResponse(200, $response);

//If user already exist

//adding the user data to response

} else if ($res == USER_ALREADY_EXISTED) {

$response["error"] = false;

$user = $db->getUser($email);

$response['id'] = $user['id'];

$response['name'] = $user['name'];

$response['email'] = $user['email'];

echoResponse(200, $response);

}

});

* URL: /send

* Method: POST

* parameters: id, message

* */

//This is used to send message on the chat room

$app->post('/send', function () use ($app) {

//Verifying required parameters

verifyRequiredParams(array('id', 'message'));

//Getting request parameters

$id = $app->request()->post('id');

$message = $app->request()->post('message');

$name = $app->request()->post('name');

//Creating a gcm object

$gcm = new GCM();

//Creating db object

$db = new DbOperation();

//Creating response array

$response = array();

//Creating an array containing message data

$pushdata = array();

//Adding title which would be the username

$pushdata['title'] = $name;

//Adding the message to be sent

$pushdata['message'] = $message;

//Adding user id to identify the user who sent the message

$pushdata['id']=$id;

//If message is successfully added to database

if ($db->addMessage($id, $message)) {

//Sending push notification with gcm object

$gcm->sendMessage($db->getRegistrationTokens($id), $pushdata);

$response['error'] = false;

} else {

$response['error'] = true;

}

echoResponse(200, $response);

});

* URL: /storegcmtoken/:id

* Method: PUT

* Parameters: token

* */

//This will store the gcm token to the database

$app->put('/storegcmtoken/:id', function ($id) use ($app) {

verifyRequiredParams(array('token'));

$token = $app->request()->put('token');

$db = new DbOperation();

$response = array();

if ($db->storeGCMToken($id, $token)) {

$response['error'] = false;

$response['message'] = "token stored";

} else {

$response['error'] = true;

$response['message'] = "Could not store token";

}

echoResponse(200, $response);

});

* URL: /messages

* Method: GET

* */

//This will fetch all the messages available on the database to display on the thread

$app->get('/messages', function () use ($app){

$db = new DbOperation();

$messages = $db->getMessages();

$response = array();

$response['error']=false;

$response['messages'] = array();

while($row = mysqli_fetch_array($messages)){

$temp = array();

$temp['id']=$row['id'];

$temp['message']=$row['message'];

$temp['userid']=$row['users_id'];

$temp['sentat']=$row['sentat'];

$temp['name']=$row['name'];

array_push($response['messages'],$temp);

}

echoResponse(200,$response);

});

//Function to validate email

function validateEmail($email)

{

$app = \Slim\Slim::getInstance();

if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {

$response["error"] = true;

$response["message"] = 'Email address is not valid';

echoResponse(400, $response);

$app->stop();

}

//Function to display the response in browser

function echoResponse($status_code, $response)

{

$app = \Slim\Slim::getInstance();

// Http response code

$app->status($status_code);

// setting response content type to json

$app->contentType('application/json');

echo json_encode($response);

}

//Function to verify required parameters

function verifyRequiredParams($required_fields)

{

$error = false;

$error_fields = "";

$request_params = $_REQUEST;

// Handling PUT request params

if ($_SERVER['REQUEST_METHOD'] == 'PUT') {

$app = \Slim\Slim::getInstance();

parse_str($app->request()->getBody(), $request_params);

}

foreach ($required_fields as $field) {

if (!isset($request_params[$field]) || strlen(trim($request_params[$field])) <= 0) {

$error = true;

$error_fields .= $field . ', ';

}

if ($error) {

// Required field(s) are missing or empty

// echo error json and stop the app

$response = array();

$app = \Slim\Slim::getInstance();

$response["error"] = true;

$response["message"] = 'Required field(s) ' . substr($error_fields, 0, -2) . ' is missing or empty';

echoResponse(400, $response);

$app->stop();

}

function authenticate(\Slim\Route $route)

{

//Implement authentication if needed

}

$app->run();

Thats it for the API Coding. Now you need a REST Client to Test the API. You can use Postman for google chrome.

Testing the API

You can use Postman for chrome or any other REST Client to test your API. The final API we built is shown in the following table

Base URL: http://localhost/SimplifiedCodingChat/v1/

URL	Method	Parameters
register	POST	name,email
send	POST	id, message
storegcmtoken/:id	PUT	token
messages	GET

If you are having some problems or troubles you can get my php project for this Android Chat App for Android Tutorial from the link given below (You need to unlock the link).

[sociallocker id=1372] Download REST API Project[/sociallocker]

So thats all for this part friends. You can follow the next part from the link given.

Create Chat Application in Android using GCM Part 2

In this part we will actually Create Chat App for Android using Android Studio. And yes feel free to ask by comments if having any troubles. Thank You 🙂