java.lang.String org.json.JSONObject.getString(java.lang.String)' on a null object reference

Question

Im getting error in the following code. I am getting error in between the --->1 & --->2 ..ie while loop. Got response code as 200.But still my app is crashed.

Note: The same question was already asked.Even I analyzed that but i m not getting the right thing.Please help me to fix it.

if (responseCode == HttpURLConnection.HTTP_OK || responseCode == HttpURLConnection.HTTP_BAD_METHOD) {

    is = con.getInputStream();
    BufferedReader br = new BufferedReader(new InputStreamReader(is));
    String line;
    Log.e("LOGIN CHECK", "json"); // -----------> 1 (Prints in Log.e)
    while ((line = br.readLine()) != null){
           buffer.append(line).append("\r\n");
    }
    json = buffer.toString();    // -----------> 2 (Didnt print in Log.e)
    Log.e("LOGIN CHECK", "json" + buffer.toString());
    is.close();
 }

LogCat Error:

 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.xxxxx.restaurant.Fragment.SignUpFragment_1$ProcessLogin.onPostExecute(SignUpFragment_1.java:187)
                                                       at com.xxxx.restaurant.Fragment.SignUpFragment_1$ProcessLogin.onPostExecute(SignUpFragment_1.java:163)
                                                       at android.os.AsyncTask.finish(AsyncTask.java:632)
                                                       at android.os.AsyncTask.access$600(AsyncTask.java:177)
                                                       at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
                                                       at android.os.Handler.dispatchMessage(Handler.java:102)
                                                       at android.os.Looper.loop(Looper.java:145)
                                                       at android.app.ActivityThread.main(ActivityThread.java:5942)
                                                       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:1400)
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)

Json PArser:

public class JSONParser {

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

    public JSONParser() {
    }

    public JSONObject getJSONFromUrl(String url, HashMap<String, String> params) {
        HttpURLConnection con = null;
        InputStream is = null;

        try {
            con = (HttpURLConnection) (new URL(url)).openConnection();
            con.setRequestMethod("POST");
            con.connect();
            OutputStream os = con.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, "UTF-8"));
            writer.write(getPostDataString(params));
            writer.flush();
            writer.close();
            os.close();
            StringBuilder buffer = new StringBuilder();
            Log.e("Response Buffer", String.valueOf(buffer));
            int responseCode = con.getResponseCode();
            Log.e("Response Code", String.valueOf(responseCode));

            if (responseCode == HttpURLConnection.HTTP_OK || responseCode == HttpURLConnection.HTTP_BAD_METHOD) {

                is = con.getInputStream();
                BufferedReader br = new BufferedReader(new InputStreamReader(is));
                String line;
                Log.e("LOGIN CHECK", "json");
                while ((line = br.readLine()) != null)
                    buffer.append(line).append("\r\n");
                json = buffer.toString();
                Log.e("LOGIN CHECK", "json" + buffer.toString());
                is.close();
            }else{
                  json = "abc";
            }
            con.disconnect();
        } catch (Throwable t) {
            t.printStackTrace();
        } finally {
            try {
                if (is != null) {
                    is.close();
                }
            } catch (Throwable ignored) {
            }
            try {
                if (con != null) {
                    con.disconnect();
                }
            } catch (Throwable ignored) {
            }
        }
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
        }
        return jObj;
    }

    private String getPostDataString(HashMap<String, String> params) throws UnsupportedEncodingException {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for (Map.Entry<String, String> entry : params.entrySet()) {
            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
        }

        return result.toString();
    }
}

SignUpFragment_1:

try {
                if (json.getString(KEY_SUCCESS) != null) {  // Error in this LINE

                    String res = json.getString(KEY_SUCCESS);

                    if (Integer.parseInt(res) == 1) {
                        dbUtil.open();
                        JSONObject json_user = json.getJSONObject("user");

                        UserFunctions logout = new UserFunctions();
                        logout.logoutUser(context);

                        dbUtil.addLogIn(strUsername, strEmail, strPassword, LogInActivity.img);
                        Intent upanel = new Intent(context, MainActivity.class);
                        upanel.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        pDialog.dismiss();
                        startActivity(upanel);
                    } else {
                        pDialog.dismiss();
                        Toast.makeText(context, "Incorrect username/password", Toast.LENGTH_SHORT).show();
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

Answer 1

The error say's that you haven't initialize your string line... so either initialize like line = "" or pass null (which will again throw NullPointerException when it accessed without assigning any value) to it..you can also try StringBuilder class like..

BufferedReader reader = new BufferedReader(new InputStreamReader(http.getInputStream()));
StringBuilder sb = new StringBuilder();
String line = null;
  while ((line = reader.readLine()) != null) {
    sb.append(line + "\n");
  }
reader.close();
json = sb.toString();            // this is your String json;

Refer my example for further detail ....

Answer 2

The Exception is JSONObject.getString(java.lang.String), so it means you are getting JSONObject which is null, so jObj is null and LogCat is not showing any Exception because of your goodness, you didn't catch exceptions.

So to work your code, replace code from else part.

You were not assigning JSONObject to json string variable in else part.

if (responseCode == HttpURLConnection.HTTP_OK || responseCode == HttpURLConnection.HTTP_BAD_METHOD) {
    is = con.getInputStream();
    BufferedReader br = new BufferedReader(new InputStreamReader(is));
    String line;
    Log.e("LOGIN CHECK", "json");
    while ((line = br.readLine()) != null)
        buffer.append(line).append("\r\n");
    json = buffer.toString();
    Log.e("LOGIN CHECK", "json" + buffer.toString());
    is.close();
} else {
      json = "{" + KEY_SUCCESS + ":\"error response code " + responseCode + " \"}";
}

And never ever forget to Catch and Log Exception

try {
    jObj = new JSONObject(json);
} catch (JSONException e) {
    e.printStackTrace();
}

I'm sure, it'll solve your problem.