java - 将 BufferedWriter 与 HTTP 结合使用时出现 IOException

Question

我遵循了有关将使用 wamp 服务器(在 Windows 上)运行的 MyQSL 数据库连接到 Android 应用程序的 youtube 教程。(视频链接为:https://www.youtube.com/watch?v=eldh8l8yPew)

在我的 Android Studio 代码中，我创建了一个扩展 AsyncTask 的类(名为“BackgroundWorker”)，它应该处理与连接到数据库的 PHP 文件的通信。

为了打开到数据库的写入 channel ，我使用了连接到 httpURLConnection 对象的 BufferedWriter 和 OutputStream，该对象具有位于 WAMPSERVER 的 www 文件夹中的相关 php 脚本的 URL。

经过这么长时间的介绍，我的问题是在尝试执行以下行时出现 IOException:

OutputStream outputStream = httpURLConnection.getOutputStream();

我几乎从视频教程中复制了整个代码，所以我怀疑它有什么问题。我更多地考虑 URL 设置的方向 - 我的 URL 对象获取具有地址的字符串:

String loginURL = "http://10.0.2.2/login.php";

其中“login.php”是我的 php 脚本，它位于 wamp 服务器的 www 文件夹中。我知道 10.0.0.2 是一种默认地址，代表 Android Emulators 中的本地主机，我怎么使用 Genymotion Emulator 所以也许这不是正确的地址？我还尝试输入我在运行 IPCONFIG 时看到的所有其他 IP 地址，但没有改变结果。

我不太擅长调试，所以我使用了 AsyncTask 的 Toasts 和 PublishProgress 方法来查找和隔离 IOException。

这是我认为可能与 IOException 相关的部分代码:

我的 BackgroundWorker 类(扩展了 AsyncTask):

public class BackgroundWorker extends AsyncTask <String , Integer , String> {
    Context context;
    AlertDialog alertDialog;
    public BackgroundWorker(Context userContext) {
        this.context = userContext;
    }

    @Override
    protected String doInBackground(String... params) {
        // Reading the arguments in the order I sent them in MainActivity
        String username = params[0];
        String pass = params[1];
        String type = params[2];

        // Making structure for updating during the wat using Toasts (and showing the first one
        int progressValue = 0;          // Before if
        publishProgress(progressValue);
        // Initial String that will hold the text to read from server
        String result = "";
        // Initial the URL String , the IP address if standart for Android LocalHost
        String loginURL = "http://10.0.2.2/login.php";
        if (type.equals("login")) {

            progressValue++;    //1
            publishProgress(progressValue);

            try {
                URL url = new URL(loginURL);

                progressValue++;    //2
                publishProgress(progressValue);

                // Building the HttpUrlConnection object
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);

                progressValue++;    //3
                publishProgress(progressValue);

                // Building the writing infrastructure
                // IOException occurs after the commit of the next line
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));

                progressValue++;    //4
                publishProgress(progressValue);

                // Building the message to the PHP script
                String post_data = URLEncoder.encode("user_name" , "UTF-8") + "=" + URLEncoder.encode(username , "UTF-8")
                        + "&" + URLEncoder.encode("user_pass" , "UTF-8") + "=" + URLEncoder.encode(pass , "UTF-8");

                progressValue++;    //5
                publishProgress(progressValue);

                // Writing the data
                bufferedWriter.write(post_data);

                progressValue++;    //6
                publishProgress(progressValue);

                // Closing all writing structures
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                // Building the Reading Infrastructure
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream , "iso-8859-1"));

                // Reading the data
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    result += line;
                }
                // Closing all reading structures
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();


            } catch (MalformedURLException e) {
                e.printStackTrace();
                progressValue = 10;
                publishProgress(progressValue);
            } catch (IOException e) {
                progressValue = 11;
                publishProgress(progressValue);
                e.printStackTrace();
            }
        }
        return result;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        int progressValue = values[0];
        // Before IF statement
        if (progressValue == 0) Toast.makeText(this.context , "Before if" , Toast.LENGTH_SHORT).show();
        // After IF statement
        if (progressValue == 1) Toast.makeText(this.context , "After if" , Toast.LENGTH_SHORT).show();
        // After URL statement
        if (progressValue == 2) Toast.makeText(this.context , "After URL Setting" , Toast.LENGTH_SHORT).show();
        // Before Writing data
        if (progressValue == 3) Toast.makeText(this.context , "After making HTML" , Toast.LENGTH_SHORT).show();
        // After Writing data
        if (progressValue == 4) Toast.makeText(this.context , "After making writing infra" , Toast.LENGTH_SHORT).show();
        // After Writing data
        if (progressValue == 5) Toast.makeText(this.context , "Before Writing data" , Toast.LENGTH_SHORT).show();
        // After Writing data
        if (progressValue == 6) Toast.makeText(this.context , "After Writing data" , Toast.LENGTH_SHORT).show();
        // After Writing data
        if (progressValue == 10) Toast.makeText(this.context , "First exception" , Toast.LENGTH_SHORT).show();
        // After Writing data
        if (progressValue == 11) Toast.makeText(this.context , "IO Exception" , Toast.LENGTH_SHORT).show();
    }

    @Override
    protected void onPreExecute() {
        alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle("Login Status");
    }

    @Override
    protected void onPostExecute(String result) {
        alertDialog.setMessage(result);
        alertDialog.show();
    }
}

这是我的 login.php 代码:

<?php
require "conn.php";
$user_name = $_POST["user_name"];
$user_pass = $_POST["user_pass"];
$mysql_qry = "select * from employee_data where user like '$user_name' and password like '$user_pass';";
$result = mysqli_query($conn ,$mysql_qry);
if(mysqli_num_rows($result) > 0) {
    echo "login success";
}
else {
    echo "login not seccess";
}
?>

conn.php 是另一个将连接与数据库建立连接的脚本。当我直接通过浏览器运行我的 login.php 脚本时 - 它工作正常。

非常感谢，我希望你能理解这个问题，诺姆

Answer 1

我自己解决了。IP 地址不正确，因为我使用 Genymotion 模拟器，所以我必须将 IP 更改为 192.168.56.1现在一切正常。