JSONParser错误 - 转换结果java.lang.NullPointerException：lock == null

Question

任何人都可以帮助我解决我目前使用JSONParser在Android Studio中遇到的错误。我在logcat中遇到以下错误。

JSONParser.java文件

package com.bradvisor.bradvisor.library;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

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

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
            Log.e("JSON", json);
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

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

        // return JSON String
        return jObj;

    }
}

UserFunction.Java文件

package com.bradvisor.bradvisor.library;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;
import android.content.Context;
import android.util.Log;

public class UserFunctions {

    private JSONParser jsonParser;

    //URL of the PHP API
    private static String loginURL =    "http://192.168.0.3:8080/bradvisor_login_api/";
    private static String registerURL = "http://192.168.0.3:8080/bradvisor_login_api/";
    private static String forpassURL =  "http://192.168.0.3:8080/bradvisor_login_api/";
    private static String chgpassURL =  "http://192.168.0.3:8080/bradvisor_login_api/";

    private static String login_tag = "login";
    private static String register_tag = "register";
    private static String forpass_tag = "forpass";
    private static String chgpass_tag = "chgpass";


    // constructor
    public UserFunctions(){
        jsonParser = new JSONParser();
    }

    /**
     * Function to Login
     **/

    public JSONObject loginUser(String email, String password){
        // Building Parameters
        List params = new ArrayList();
        params.add(new BasicNameValuePair("tag", login_tag));
        params.add(new BasicNameValuePair("email", email));
        params.add(new BasicNameValuePair("password", password));
        JSONObject json = jsonParser.getJSONFromUrl(loginURL, params);
        return json;
    }

    /**
     * Function to change password
     **/

    public JSONObject chgPass(String newpas, String email){
        List params = new ArrayList();
        params.add(new BasicNameValuePair("tag", chgpass_tag));

        params.add(new BasicNameValuePair("newpas", newpas));
        params.add(new BasicNameValuePair("email", email));
        JSONObject json = jsonParser.getJSONFromUrl(chgpassURL, params);
        return json;
    }

    /**
     * Function to reset the password
     **/

    public JSONObject forPass(String forgotpassword){
        List params = new ArrayList();
        params.add(new BasicNameValuePair("tag", forpass_tag));
        params.add(new BasicNameValuePair("forgotpassword", forgotpassword));
        JSONObject json = jsonParser.getJSONFromUrl(forpassURL, params);
        return json;
    }

    /**
     * Function to  Register
     **/
    public JSONObject registerUser(String fname, String lname, String email, String uname, String password){
        // Building Parameters
        List params = new ArrayList();
        params.add(new BasicNameValuePair("tag", register_tag));
        params.add(new BasicNameValuePair("fname", fname));
        params.add(new BasicNameValuePair("lname", lname));
        params.add(new BasicNameValuePair("email", email));
        params.add(new BasicNameValuePair("uname", uname));
        params.add(new BasicNameValuePair("password", password));
        JSONObject json = jsonParser.getJSONFromUrl(registerURL,params);
        return json;
    }

    /**
     * Function to logout user
     * Resets the temporary data stored in SQLite Database
     * */
    public boolean logoutUser(Context context){
        DatabaseHandler db = new DatabaseHandler(context);
        db.resetTables();
        return true;
    }

}

Register.java文件错误

private class ProcessRegister extends AsyncTask<String, String, JSONObject> {

        /**
         * Defining Process dialog
         **/
        private ProgressDialog pDialog;

        String email,password,fname,lname,uname;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            inputUsername = (EditText) findViewById(R.id.uname);
            inputPassword = (EditText) findViewById(R.id.pword);
            fname = inputFirstName.getText().toString();
            lname = inputLastName.getText().toString();
            email = inputEmail.getText().toString();
            uname= inputUsername.getText().toString();
            password = inputPassword.getText().toString();
            pDialog = new ProgressDialog(Register.this);
            pDialog.setTitle("Contacting Servers");
            pDialog.setMessage("Registering ...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(true);
            pDialog.show();
        }

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


            UserFunctions userFunction = new UserFunctions();
            JSONObject json = userFunction.registerUser(fname, lname, email, uname, password);

            return json;


        }
        @Override
        protected void onPostExecute(JSONObject json) {
            /**
             * Checks for success message.
             **/
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    registerErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS);

                    String red = json.getString(KEY_ERROR);

                    if(Integer.parseInt(res) == 1){
                        pDialog.setTitle("Getting Data");
                        pDialog.setMessage("Loading Info");

                        registerErrorMsg.setText("Successfully Registered");


                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        /**
                         * Removes all the previous data in the SQlite database
                         **/

                        UserFunctions logout = new UserFunctions();
                        logout.logoutUser(getApplicationContext());
                        db.addUser(json_user.getString(KEY_FIRSTNAME),json_user.getString(KEY_LASTNAME),json_user.getString(KEY_EMAIL),json_user.getString(KEY_USERNAME),json_user.getString(KEY_UID),json_user.getString(KEY_CREATED_AT));
                        /**
                         * Stores registered data in SQlite Database
                         * Launch Registered screen
                         **/

                        Intent registered = new Intent(getApplicationContext(), Registered.class);

                        /**
                         * Close all views before launching Registered screen
                         **/
                        registered.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        pDialog.dismiss();
                        startActivity(registered);


                        finish();
                    }

                    else if (Integer.parseInt(red) ==2){
                        pDialog.dismiss();
                        registerErrorMsg.setText("User already exists");
                    }
                    else if (Integer.parseInt(red) ==3){
                        pDialog.dismiss();
                        registerErrorMsg.setText("Invalid Email id");
                    }

                }


                else{
                    pDialog.dismiss();

                    registerErrorMsg.setText("Error occured in registration");
                }

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


            }
        }}
    public void NetAsync(View view){
        new NetCheck().execute();
    }}

LogCat

E/Buffer Error﹕ Error converting result java.lang.NullPointerException: lock == null
  E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of

 E/AndroidRuntime﹕ FATAL EXCEPTION: main
        Process: com.bradvisor.bradvisor, PID: 1922
        java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.getString(java.lang.String)' on a null object reference
                at com.bradvisor.bradvisor.Register$ProcessRegister.onPostExecute(Register.java:231)
                at com.bradvisor.bradvisor.Register$ProcessRegister.onPostExecute(Register.java:188)
                at android.os.AsyncTask.finish(AsyncTask.java:636)
                at android.os.AsyncTask.access$500(AsyncTask.java:177)
                at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5257)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

LogCat 231指的是

行

if (json.getString(KEY_SUCCESS) != null) {