I have followed this link in making an app that lets users log in with database http://www.mybringback.com/tutorial-series/13239/android-mysql-php-json-part-6-json-parsing-and-android-design/
But after logging in it crashes. I have searched for hours and have read some questions that have the same problem but none of the solutions worked for me.
I am trying to run it in the android emulator.
Login.java
package com.example.mysqltest;
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 Login extends Activity implements OnClickListener {
private EditText user, pass;
private Button mSubmit, mRegister;
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class
// 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:
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
// setup input fields
user = (EditText) findViewById(R.id.username);
pass = (EditText) findViewById(R.id.password);
// 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, Register.class);
startActivity(i);
break;
default:
break;
}
}
class AttemptLogin extends AsyncTask<String, String, String> {
private static final String LOGIN_URL = "http://127.0.0.1:1234/webservice/login.php";
// testing from a real server:
// private static final String LOGIN_URL =
// "http://www.mybringback.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";
boolean failure = false;
String username, password;
@Override
protected void onPreExecute() {
super.onPreExecute();
username = user.getText().toString();
password = pass.getText().toString();
pDialog = new ProgressDialog(Login.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;
JSONParser jsonParser = new JSONParser();
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());
// save user data
SharedPreferences sp = PreferenceManager
.getDefaultSharedPreferences(Login.this);
Editor edit = sp.edit();
edit.putString("username", username);
edit.commit();
Intent i = new Intent(Login.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(Login.this, file_url, Toast.LENGTH_LONG).show();
}
}
}
}
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 = "webservice";
// 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($_COOKIE);
}
// This tells the web browser that your content is encoded using UTF-8
// and that it should submit content back to you using UTF-8
header('Content-Type: text/html; charset=utf-8');
// This initializes a session. Sessions are used to store information about
// a visitor from one web page visit to the next. Unlike a cookie, the information is
// stored on the server-side and cannot be modified by the visitor. However,
// note that in most cases sessions do still use cookies and require the visitor
// to have cookies enabled. For more information about sessions:
// http://us.php.net/manual/en/book.session.php
session_start();
// Note that it is a good practice to NOT end your PHP files with a closing PHP tag.
// This prevents trailing newlines on the file from being included in your output,
// which can cause problems with redirecting users.
?>
Login.php
<?php
//load and connect to MySQL database stuff
require("config.inc.php");
if (!empty($_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
}
?>
The Logcat report
09-20 11:02:38.196: E/AndroidRuntime(913): FATAL EXCEPTION: AsyncTask #1
09-20 11:02:38.196: E/AndroidRuntime(913): Process: com.example.mysqltest, PID: 913
09-20 11:02:38.196: E/AndroidRuntime(913): java.lang.RuntimeException: An error occured while executing doInBackground()
09-20 11:02:38.196: E/AndroidRuntime(913): at android.os.AsyncTask$3.done(AsyncTask.java:300)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
09-20 11:02:38.196: E/AndroidRuntime(913): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.lang.Thread.run(Thread.java:841)
09-20 11:02:38.196: E/AndroidRuntime(913): Caused by: java.lang.NullPointerException
09-20 11:02:38.196: E/AndroidRuntime(913): at com.example.mysqltest.Login$AttemptLogin.doInBackground(Login.java:131)
09-20 11:02:38.196: E/AndroidRuntime(913): at com.example.mysqltest.Login$AttemptLogin.doInBackground(Login.java:1)
09-20 11:02:38.196: E/AndroidRuntime(913): at android.os.AsyncTask$2.call(AsyncTask.java:288)
09-20 11:02:38.196: E/AndroidRuntime(913): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
09-20 11:02:38.196: E/AndroidRuntime(913): ... 4 more
