Logging в причинах андроид приложение к сбою

Question

Я следовал этой ссылке в создании приложение, которое позволяет пользователям войти с базой данных http://www.mybringback.com/tutorial-series/13239/android-mysql-php-json-part-6-json-parsing-and-android-design/

Но после входа в систему он выходит из строя. Я искал часы и прочитал некоторые вопросы, которые имеют одинаковую проблему, но ни одно из решений не сработало для меня.

Я пытаюсь запустить его в эмуляторе Android.

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 
} 

?> 

Отчет Logcat

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 

Answer 1

JSONParser - это собственный пользовательский класс для выборки и разбора?

В любом случае, если в нашем методе пользовательского класса есть исключение, ответ может иметь нулевой смысл? Но ваш не проверяющий объект имеет значение null или нет. без проверки непосредственно ур печатает значение json.tostring(); Если ur json имеет значение null, он генерирует только nullpointerexception. Попробуйте изменить ниже код и отметьте один раз.

заменить код из

JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST", 
         params); 

в

DefaultHttpClient httpclient = new DefaultHttpClient(); 
HttpPost httppost = new HttpPost(url); 
HttpResponse httpresponse = httpclient.execute(httppost); 
HttpEntity httpentity = httpresponse.getEntity(); 
JSONObject json = null; 
if(TextUtils.isEmpty(EntityUtils.toString(httpentity))) { 
    Log.d("Login attempt", "Json is empty or null"); 
} else { 
    json = new JSONObject(EntityUtils.toString(httpentity)); 
}