java - 从服务器接收响应时出错？

Question

我正在制作一个应用程序，将一些数据存储在数据库中，然后检索它。在服务器端我使用 PHP，在客户端我有这个文件来获取输入并将其传递给 PHP 文件。

new AsyncTask<String, String, String>() {

                JSONParser jsonParser = new JSONParser();
                private ProgressBar pBar;
                private String url_post_pet = "http://192.168.0.13/Android/post_pet.php";

                // JSON Node names
                private static final String TAG_SUCCESS = "success";

                /**
                 * Before starting background thread Show Progress Dialog
                 */
                @Override
                protected void onPreExecute() {
                    super.onPreExecute();
                    //pBar = new ProgressBar();
                    //pBar.setIndeterminate(false);
                    //pBar.setVisibility(View.VISIBLE);
                }

                @Override
                protected String doInBackground(String... args) {
                    // Building Parameters
                    HashMap<String, String> params = new HashMap<>();
                    params.put("name", a);
                    params.put("breed", BREED);
                    params.put("type", TYPE);
                    params.put("images", "Whatever");
                    params.put("description", c);
                    params.put("coords", b);

                    // getting JSON Object
                    // Note that create product url accepts POST method
                    JSONObject json = jsonParser.makeHttpRequest(url_post_pet,
                            "POST", params);
                    // check log cat for response
                    Log.d("Create Response", json.toString());

                    // check for success tag
                    try {
                        int success = json.getInt(TAG_SUCCESS);

                        if (success == 1) {
                            // successfully created product
                            Intent i = new Intent(getApplicationContext(), MainActivity.class);
                            startActivity(i);

                            // closing this screen
                            finish();
                        } else {
                            // failed to create product
                        }
                    } catch (JSONException e) {
                        System.out.println("exception" + e);
                        e.printStackTrace();
                    }
                    System.out.println("nul");
                    return null;
                }

                /**
                 * After completing background task Dismiss the progress dialog
                 **/
                protected void onPostExecute(String file_url) {
                    // dismiss the dialog once done
                    //pBar.dismiss();
                }
            }.execute();

        }
    });
}

另外，我有这个 JSONParser:

public class JSONParser {

String charset = "UTF-8";
HttpURLConnection conn;
DataOutputStream wr;
StringBuilder result;
URL urlObj;
JSONObject jObj = null;
StringBuilder sbParams;
String paramsString;

public JSONObject makeHttpRequest(String url, String method,
                                  HashMap<String, String> params) {

    sbParams = new StringBuilder();
    int i = 0;
    for (String key : params.keySet()) {
        try {
            if (i != 0){
                sbParams.append("&");
            }
            sbParams.append(key).append("=")
                    .append(URLEncoder.encode(params.get(key), charset));

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        i++;
    }

    if (method.equals("POST")) {
        // request method is POST
        try {
            urlObj = new URL(url);
            conn = (HttpURLConnection) urlObj.openConnection();
            conn.setDoOutput(true);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Accept-Charset", charset);
            conn.setReadTimeout(10000);
            conn.setConnectTimeout(15000);
            conn.connect();

            paramsString = sbParams.toString();

            wr = new DataOutputStream(conn.getOutputStream());
            wr.writeBytes(paramsString);
            wr.flush();
            wr.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    else if(method.equals("GET")){
        // request method is GET

        if (sbParams.length() != 0) {
            url += "?" + sbParams.toString();
        }

        try {
            urlObj = new URL(url);
            conn = (HttpURLConnection) urlObj.openConnection();
            conn.setDoOutput(false);
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Accept-Charset", charset);
            conn.setConnectTimeout(15000);
            conn.connect();

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    try {
        //Receive the response from the server
        InputStream in = new BufferedInputStream(conn.getInputStream());
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        result = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            result.append(line);
        }

        Log.d("JSON Parser", "result: " + result.toString());
    } catch (IOException e) {
        e.printStackTrace();
    }

    conn.disconnect();

    // try parse the string to a JSON object
    try {
        System.out.println(jObj);
        jObj = new JSONObject(result.toString());
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON Object
    return jObj;
}

这是我每次提交数据时遇到的错误:

08-26 12:51:08.236 5089-5156/chtecnologies.myapplication D/JSON Parser: result:08-26 12:51:08.239 5089-5156/chtecnologies.myapplication E/JSON Parser: Error parsing data org.json.JSONException: End of input at character 0 of 08-26 12:51:08.793 5089-5096/chtecnologies.myapplication W/art: Suspending all threads took: 190.496ms 08-26 12:51:09.245 5089-5096/chtecnologies.myapplication W/art: Suspending all threads took: 137.277ms 08-26 12:51:09.267 5089-5156/chtecnologies.myapplication E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1 Process: chtecnologies.myapplication, PID: 5089 java.lang.RuntimeException: An error occured while executing doInBackground() at android.os.AsyncTask$3.done(AsyncTask.java:304) at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) at java.util.concurrent.FutureTask.setException(FutureTask.java:222) at java.util.concurrent.FutureTask.run(FutureTask.java:242) at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) at java.lang.Thread.run(Thread.java:818) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.toString()' on a null object reference at chtecnologies.myapplication.PostPet$4$1.doInBackground(PostPet.java:154) at chtecnologies.myapplication.PostPet$4$1.doInBackground(PostPet.java:118) at android.os.AsyncTask$2.call(AsyncTask.java:292) at java.util.concurrent.FutureTask.run(FutureTask.java:237) at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)  at java.lang.Thread.run(Thread.java:818) 

数据成功进入数据库，但 JSONParser 似乎有问题，无法获取 PHP 文件的结果。

您能告诉我 JSONParser 文件或其他地方是否有问题吗？这是我第一次在我的应用程序中实现服务器，我希望你能帮助我!谢谢

Answer 1

您发送数据的方式看起来很可疑。如果您想在 POST 中发送数据，请使用 HttpURLConnection 就像

String postParam = "name=" + a + "&breed=" + BREED + "&type=" + "&images=" +
        Whatever + "&description=" + c + "&coords=" + b;

try {
    URL url = new URL(url);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();

    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");

    OutputStream os = connection.getOutputStream();
    os.write(postParam.getBytes());
    os.flush();
    os.close();

    // Fetching the response code
    responseCode = connection.getResponseCode();
    Log.d(TAG, "POST Response Code: " + responseCode);
} catch (Exception e) {
    e.printStackTrace();
}

connection.setRequestMethod- 设置您想要使用 GET/POST 发送数据的方法

connection.setDoOutput(true)- 让您发送输出

connection.setDoInput(true)-让您在发送数据后接收输入(如果有)

希望这能解决您的问题!