JSON對象返回null（android + json + php + mysql）

Question

我有一個註冊表單，我在進行驗證。 用戶切換關注電子郵件字段後，我想檢查是否在數據庫中註冊了此類電子郵件，並對其進行敬酒。 不管我做什麼，不過，我總是得到線585空指針異常是以下行：

Log.d("Checking wether this email exists in database", json.toString()); 

這裏是整個事情：

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

     int success; 

     @Override 
     protected String doInBackground(String... args) { 

      int success; 
      try { 
       // Building Parameters 
       List<NameValuePair> params = new ArrayList<NameValuePair>(); 
       Log.d("Kylie", userEmail); 
       params.add(new BasicNameValuePair("user_email", userEmail)); 

       Log.d("request!", "starting"); 

       // Posting user data to script 
       JSONObject json = jsonParser.makeHttpRequest(CHECK_EMAIL_EXISTS_URL, "POST", params); 

       // full json response 
       Log.d("Checking wether this email exists in database", json.toString()); 

       // json success element 
       success = json.getInt(TAG_SUCCESS); 
       if (success == 1) { 
        Log.d("Email exists", json.toString()); 
        finish(); //fire up an alarm 
        userWithTheSameEmail = true; 
        return json.getString(TAG_MESSAGE); 
       } else if(success == 2) { 
        Log.d("Email doesnt exist", json.getString(TAG_MESSAGE)); 
        userWithTheSameEmail = false; 
        return json.getString(TAG_MESSAGE); 
       } else { 
        Log.d("Something happened", json.getString(TAG_MESSAGE)); 
        userWithTheSameEmail = false; 
        return json.getString(TAG_MESSAGE); 
       } 
      } catch (JSONException e) { 
       e.printStackTrace(); 
      } 

      return null; 

     } 

這裏是PHP腳本接受的JSON：

<?php 

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



if (!empty($_POST)) { 
    //gets user's info based off of a username. 

    $user_email = mysql_real_escape_string($_POST['user_email']; 
    #$user_email_to_query = "\"". $user_email . "\""; 
    $query = " 
      SELECT 
       user_email 
      FROM users 
      WHERE 
       user_email = '$user_email' 
     "; 

    if (mysql_num_rows($row) > 0) { 
     $response["success"] = 1; 
     $response["message"] = "User with such email exists"; 
    } else { 
     $response["success"] = 2; 
     $response["message"] = "User with such email doesnt exist. You can continue registering"; 
    } 
} else { 
    die("Another brick in the wall"); 
} 

下面是配置：

<?php 

    $username = "asd_asd"; 
    $password = "123123"; 
    $host = "localhost"; 
    $dbname = "asd_asd"; 


    $options = array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8'); 


    try 
    { 

     $db = new PDO("mysql:host={$host};dbname={$dbname};charset=utf8", $username, $password, $options); 
    } 
    catch(PDOException $ex) 
    { 

     die("Failed to connect to the database: " . $ex->getMessage()); 
    } 

    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 

    $db->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC); 


    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(); 

這是表：

CREATE TABLE IF NOT EXISTS `users` (
    `user_id` int(11) NOT NULL AUTO_INCREMENT, 
    `user_name` varchar(30) NOT NULL, 
    `user_email` varchar(50) NOT NULL, 
    `user_password` varchar(100) NOT NULL, 
    `user_sex` varchar(10) NOT NULL, 
    `user_avatar` varchar(100) DEFAULT NULL, 
    `user_date_registered` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    `user_last_seen` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', 
    `user_points` int(11) NOT NULL, 
    PRIMARY KEY (`user_id`), 
    UNIQUE KEY `user_name` (`user_name`,`user_email`), 
    KEY `user_id` (`user_id`) 
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ; 

這是錯誤的堆棧跟蹤：

D/Kylie(4458): hdhdu@jfjd.com 
D/request!(4458): starting 
Error parsing data org.json.JSONException: Value <br of type java.lang.String cannot be converted to JSONObject 
threadid=9: thread exiting with uncaught exception (group=0x4001e578) 
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:274) 
at java.util.concurrent.FutureTask.setException(FutureTask.java:125) 
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:308) 
at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1088) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:581) 
at java.lang.Thread.run(Thread.java:1019) 
Caused by: java.lang.NullPointerException 
net.asdasd.activities.Signup$CheckWetherAUserWithSuchEmailExists.doInBackground(Signup.java:585) 
at net.asdasd.activities.Signup$CheckWetherAUserWithSuchEmailExists.doInBackground(Signup.java:1) 
at android.os.AsyncTask$2.call(AsyncTask.java:185) 
java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:306) 
... 4 more 

如果有任何我應該提供更多信息，身份證很樂意這樣做。

Answer 1

據我所見，在你的PHP代碼中沒有任何地方你實際上做了json OUTPUT。你生成一個數組，但不要對它做任何事情。

應該有一個

if (!empty($_POST)) { 
    ... blah blah blah... 
    echo json_encode($response); // <<---this is missing, apparently 
} else { 
    echo json_encode('Something blew up'); 
} 

還要注意如何我已經改變了else子句也輸出JSON。如果您希望在遠程端使用JSON，那麼您輸出的所有內容都應該是JSON。否則，你會嘗試解碼不是json的東西，並最終導致異常或至少未定義的行爲。