Android studio 应用程序与 mysql 的连接

Question

我正在尝试将我的 android studio 应用程序与 mysql 数据库连接，但在此期间我遇到了一些麻烦。我做了一个简单的登录，还有一个与 db 连接的 php 文件。

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();
            }

        }
    }
}

还有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
}

在 config.inc.php 中

<?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(); 

运行应用程序时显示的问题是：

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)

我是安卓工作室的新手。我真的需要一些帮助

Answer 1

如果您尝试通过模拟器进行连接，请使用 IP 地址 10.0.2.2 而不是 127.0.0.1 。这个link 会更多地谈论它。

Answer 2

构建与网络服务器通信的应用程序因此构建两个（或更多）应用程序通信是计算机编程中最困难的事情之一，因为很难知道哪一方有问题（有时，两者都是......）。

我建议您使用一个非常成功的起点：单独从 PHP 端编程开始。只需在使用您放置参数的 URL 时调用它。当它“回显”时，当您通过网络浏览器调用 PHP 时，您将看到结果。 当这没问题时，在你的 PHP 中添加一个“日志”系统。像这样：

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
}

将其用作（例如）： debug_log("在第一个循环内");

这是非常“基本”的，但这将保存在磁盘上而不是“回显”，这不会干扰 Android 应用程序，但可以让你看看你的 PHP 正在做什么。

完成此操作后，请返回 Android 开发者，因为这一次，您将确定，如果出现问题，它在 Android 端。