Android studio application connection with mysql

Question

I am trying to connect my android studio app with mysql database but I am having some troubles during this. I have made a simple login and also php files wich connect with db.

public class AnprSdkMain extends Activity implements OnClickListener{

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

    // Progress Dialog
    private ProgressDialog pDialog;

    // JSON parser class
    JSONParser jsonParser = new JSONParser();

    //php login script location:

    //localhost :
    //testing on your device
    //put your local ip instead,  on windows, run CMD > ipconfig
    //or in mac's terminal type ifconfig and look for the ip under en0 or en1
    // private static final String LOGIN_URL = "http://xxx.xxx.x.x:1234/webservice/login.php";

    //testing on Emulator:
    private static final String LOGIN_URL = "http://127.0.0.1/anpr/webservice/login.php";

    //testing from a real server:
    //private static final String LOGIN_URL = "http://www.yourdomain.com/webservice/login.php";

    //JSON element ids from repsonse of php script:
    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.main);

        //setup input fields
        user = (EditText)findViewById(R.id.editText1);
        pass = (EditText)findViewById(R.id.editText2);

        //setup buttons
        mSubmit = (Button)findViewById(R.id.button1);

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

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch (v.getId()) {
            case R.id.button1:
                new AttemptLogin().execute();
                break;
            default:
                break;
        }
    }

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

        /**
         * Before starting background thread Show Progress Dialog
         * */
        boolean failure = false;

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

        @Override
        protected String doInBackground(String... args) {
            // TODO Auto-generated method stub
            // Check for success tag
            int success;
            String username = user.getText().toString();
            String password = pass.getText().toString();
            try {
                // Building Parameters
                List<NameValuePair> params = new ArrayList<NameValuePair>();
                params.add(new BasicNameValuePair("username", 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());
                    Intent i = new Intent(AnprSdkMain.this, Lista.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;

        }
        /**
         * After completing background task Dismiss the progress dialog
         * **/
        protected void onPostExecute(String file_url) {
            // dismiss the dialog once product deleted
            pDialog.dismiss();
            if (file_url != null){
                Toast.makeText(AnprSdkMain.this, file_url, Toast.LENGTH_LONG).show();
            }

        }
    }
}

And login.php

//load and connect to MySQL database stuff
require("config.inc.php");

if (!empty($_POST)) {
    //gets user's info based off of a username.
    $query = " 
            SELECT 
                id, 
                username, 
                password
            FROM users 
            WHERE 
                username = :username 
        ";

    $query_params = array(
        ':username' => $_POST['username']
    );

    try {
        $stmt   = $db->prepare($query);
        $result = $stmt->execute($query_params);
    }
    catch (PDOException $ex) {
        // For testing, you could use a die and message. 
        //die("Failed to run query: " . $ex->getMessage());

        //or just use this use this one to product JSON data:
        $response["success"] = 0;
        $response["message"] = "Database Error1. Please Try Again!";
        die(json_encode($response));

    }

    //This will be the variable to determine whether or not the user's information is correct.
    //we initialize it as false.
    $validated_info = false;

    //fetching all the rows from the query
    $row = $stmt->fetch();
    if ($row) {
        //if we encrypted the password, we would unencrypt it here, but in our case we just
        //compare the two passwords
        if ($_POST['password'] === $row['password']) {
            $login_ok = true;
        }
    }

    // If the user logged in successfully, then we send them to the private members-only page 
    // Otherwise, we display a login failed message and show the login form again 
    if ($login_ok) {
        $response["success"] = 1;
        $response["message"] = "Login successful!";
        die(json_encode($response));
    } else {
        $response["success"] = 0;
        $response["message"] = "Invalid Credentials!";
        die(json_encode($response));
    }
} else {
?>
        <h1>Login</h1> 
        <form action="login.php" method="post"> 
            Username:<br /> 
            <input type="text" name="username" placeholder="username" /> 
            <br /><br /> 
            Password:<br /> 
            <input type="password" name="password" placeholder="password" value="" /> 
            <br /><br /> 
            <input type="submit" value="Login" /> 
        </form> 
        <a href="register.php">Register</a>
    <?php
}

And in config.inc.php

<?php 

    // These variables define the connection information for your MySQL database 
    // This is also for the Xampp example,  if you are hosting on your own server,
    //make the necessary changes (mybringback_travis, etc.)
    $username = "root"; 
    $password = ""; 
    $host = "127.0.0.1"; 
    $dbname = "anprscout"; 


    // UTF-8 is a character encoding scheme that allows you to conveniently store 
    // a wide varienty of special characters, like ¢ or €, in your database. 
    // By passing the following $options array to the database connection code we 
    // are telling the MySQL server that we want to communicate with it using UTF-8 
    // See Wikipedia for more information on UTF-8: 
    // http://en.wikipedia.org/wiki/UTF-8 
    $options = array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8'); 

    // A try/catch statement is a common method of error handling in object oriented code. 
    // First, PHP executes the code within the try block.  If at any time it encounters an 
    // error while executing that code, it stops immediately and jumps down to the 
    // catch block.  For more detailed information on exceptions and try/catch blocks: 
    // http://us2.php.net/manual/en/language.exceptions.php 
    try 
    { 
        // This statement opens a connection to your database using the PDO library 
        // PDO is designed to provide a flexible interface between PHP and many 
        // different types of database servers.  For more information on PDO: 
        // http://us2.php.net/manual/en/class.pdo.php 
        $db = new PDO("mysql:host={$host};dbname={$dbname};charset=utf8", $username, $password, $options); 
    } 
    catch(PDOException $ex) 
    { 
        // If an error occurs while opening a connection to your database, it will 
        // be trapped here.  The script will output an error and stop executing. 
        // Note: On a production website, you should not output $ex->getMessage(). 
        // It may provide an attacker with helpful information about your code 
        // (like your database username and password). 
        die("Failed to connect to the database: " . $ex->getMessage()); 
    } 

    // This statement configures PDO to throw an exception when it encounters 
    // an error.  This allows us to use try/catch blocks to trap database errors. 
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 

    // This statement configures PDO to return database rows from your database using an associative 
    // array.  This means the array will have string indexes, where the string value 
    // represents the name of the column in your database. 
    $db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC); 

    // This block of code is used to undo magic quotes.  Magic quotes are a terrible 
    // feature that was removed from PHP as of PHP 5.4.  However, older installations 
    // of PHP may still have magic quotes enabled and this code is necessary to 
    // prevent them from causing problems.  For more information on magic quotes: 
    // http://php.net/manual/en/security.magicquotes.php 
    if(function_exists('get_magic_quotes_gpc') && get_magic_quotes_gpc()) 
    { 
        function undo_magic_quotes_gpc(&$array) 
        { 
            foreach($array as &$value) 
            { 
                if(is_array($value)) 
                { 
                    undo_magic_quotes_gpc($value); 
                } 
                else 
                { 
                    $value = stripslashes($value); 
                } 
            } 
        } 

        undo_magic_quotes_gpc($_POST); 
        undo_magic_quotes_gpc($_GET); 
        undo_magic_quotes_gpc($_COOKIE); 
    } 
    header('Content-Type: text/html; charset=utf-8'); 
    session_start(); 

The problem that is shown when run the applications are:

07-28 18:15:34.815      340-347/com.birdorg.anpr.sdk.simple.camera.example E/Buffer Error﹕ Error converting result java.lang.NullPointerException
07-28 18:15:34.815      340-347/com.birdorg.anpr.sdk.simple.camera.example E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of
07-28 18:15:34.825      340-347/com.birdorg.anpr.sdk.simple.camera.example W/dalvikvm﹕ threadid=7: thread exiting with uncaught exception (group=0x4001d800)
07-28 18:15:34.855      340-347/com.birdorg.anpr.sdk.simple.camera.example E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:200)
            at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
            at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
            at java.util.concurrent.FutureTask.run(FutureTask.java:137)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
            at java.lang.Thread.run(Thread.java:1096)
     Caused by: java.lang.NullPointerException
            at com.birdorg.anpr.sdk.simple.camera.example.AnprSdkMain$AttemptLogin.doInBackground(AnprSdkMain.java:116)
            at com.birdorg.anpr.sdk.simple.camera.example.AnprSdkMain$AttemptLogin.doInBackground(AnprSdkMain.java:80)
            at android.os.AsyncTask$2.call(AsyncTask.java:185)
            at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
            at java.util.concurrent.FutureTask.run(FutureTask.java:137)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
            at java.lang.Thread.run(Thread.java:1096)
07-28 18:15:35.025      340-340/com.birdorg.anpr.sdk.simple.camera.example W/IInputConnectionWrapper﹕ showStatusIcon on inactive InputConnection
07-28 18:15:35.724      340-340/com.birdorg.anpr.sdk.simple.camera.example E/WindowManager﹕ Activity com.birdorg.anpr.sdk.simple.camera.example.AnprSdkMain has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@4a22d5a0 that was originally added here
    android.view.WindowLeaked: Activity com.birdorg.anpr.sdk.simple.camera.example.AnprSdkMain has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@4a22d5a0 that was originally added here
            at android.view.ViewRoot.<init>(ViewRoot.java:247)
            at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
            at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
            at android.view.Window$LocalWindowManager.addView(Window.java:424)
            at android.app.Dialog.show(Dialog.java:241)
            at com.birdorg.anpr.sdk.simple.camera.example.AnprSdkMain$AttemptLogin.onPreExecute(AnprSdkMain.java:94)
            at android.os.AsyncTask.execute(AsyncTask.java:391)
            at com.birdorg.anpr.sdk.simple.camera.example.AnprSdkMain.onClick(AnprSdkMain.java:73)
            at android.view.View.performClick(View.java:2408)
            at android.view.View$PerformClick.run(View.java:8816)
            at android.os.Handler.handleCallback(Handler.java:587)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:123)
            at android.app.ActivityThread.main(ActivityThread.java:4627)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:521)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
            at dalvik.system.NativeStart.main(Native Method)

I am new at android studio. I really need some help with this

Answer 1

If you are trying to connect through emulator, the use the IP address 10.0.2.2 instead of 127.0.0.1 . This link talks more about it.

Answer 2

Building app communicating with web server so building two apps (or maybe more) communicating is one of the most difficult thing in computer programming because it's hard to know which side is buggy (and sometimes, both are...).

I suggest you one starting point I use with great succes: start by programming, alone, the PHP side. Just call it while using URL on which you put parameter. When it will "echo", as you're calling the PHP via your web brower, you'll see the result. When this is OK, add a "log" system in you PHP. Like this:

function debug_log($string_db)
{
    // Prepare string with date and time
    $the_date = date("[ d/m/Y - H:i:s ] ");
    $to_save = $the_date.$string_db."\r";   // and add the string to log

    // Open file: write at he the end
    $handle = fopen("call.log","a");

    // Save string
    fwrite($handle,$to_save,strlen($to_save));

    fclose($handle);    // bye bye
}

Use it as (eg): debug_log ("Inside first loop");

It's very "basic", but this will save on disk and not "echo", this will not disturb the Android App but will allow you to take a look at what you PHP is doing.

Once you have done that, turn back to the Android dev as, as this time, you will be sure that, in case of problem, it's on the Android side.