JSonException :value of type java.lang.string cannot be converted to JSonObject

Question

I am developing a android registration and login form using php api and mysql. I am getting expected json result in logcat but the result is not showing on my app.Here is my codes:

<?php

/**
* File to handle all API requests
* Accepts GET and POST
* 
* Each request will be identified by TAG
* Response will be JSON data

/**
* check for POST request 
*/
if (isset($_POST['tag']) && $_POST['tag'] != '') {
// get tag
$tag = $_POST['tag'];

// include db handler
require_once 'include/DB_Functions.php';
$db = new DB_Functions();

// response Array
$response = array("tag" => $tag, "error" => FALSE);

// check for tag type
if ($tag == 'login') {
    // Request type is check Login
    $email = $_POST['email'];
    $password = $_POST['password'];

    // check for user
    $user = $db->getUserByEmailAndPassword($email, $password);
    if ($user != false) {
        // user found
        $response["error"] = FALSE;
        $response["uid"] = $user["unique_id"];
        $response["user"]["name"] = $user["name"];
        $response["user"]["email"] = $user["email"];
        $response["user"]["created_at"] = $user["created_at"];
        $response["user"]["updated_at"] = $user["updated_at"];
        echo json_encode($response);
    } else {
        // user not found
        // echo json with error = 1
        $response["error"] = TRUE;
        $response["error_msg"] = "Incorrect email or password!";
        echo json_encode($response);
    }
} else if ($tag == 'register') {
    // Request type is Register new user
    $name = $_POST['name'];
    $email = $_POST['email'];
    $password = $_POST['password'];

    // check if user is already existed
    if ($db->isUserExisted($email)) {
        // user is already existed - error response
        $response["error"] = TRUE;
        $response["error_msg"] = "User already existed";
        echo json_encode($response);
    } else {
        // store user
        $user = $db->storeUser($name, $email, $password);
        if ($user) {
            // user stored successfully
            $response["error"] = FALSE;
            $response["uid"] = $user["unique_id"];
            $response["user"]["name"] = $user["name"];
            $response["user"]["email"] = $user["email"];
            $response["user"]["created_at"] = $user["created_at"];
            $response["user"]["updated_at"] = $user["updated_at"];
            echo json_encode($response);
        } else {
            // user failed to store
            $response["error"] = TRUE;
            $response["error_msg"] = "Error occured in Registartion";
            echo json_encode($response);
        }
    }
  } else {
    // user failed to store
    $response["error"] = TRUE;
    $response["error_msg"] = "Unknown 'tag' value.should be either'or;
    echo json_encode($response);
 }
} else {
$response["error"] = TRUE;
$response["error_msg"] = "Required parameter 'tag' is missing!";
echo json_encode($response);
}
?>

It handles all requests from login and registration activity. Below i am posting those as well.This is RegisterActivity:

package com.indiainhand.iih;

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

  import com.android.volley.Request;
   import com.android.volley.Response;
 import com.android.volley.VolleyError;
     import com.android.volley.toolbox.StringRequest;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.HashMap;
import java.util.Map;


public class RegisterActivity extends Activity {
private static final String TAG = RegisterActivity.class.getSimpleName();
private Button btnRegister;
private Button btnLinkToLogin;
private EditText inputFullName;
private EditText inputEmail;
private EditText inputPassword;
private ProgressDialog pDialog;
private SessionManager session;
private SQLiteHandler db;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_register);

    inputFullName = (EditText) findViewById(R.id.name);
    inputEmail = (EditText) findViewById(R.id.email);
    inputPassword = (EditText) findViewById(R.id.password);
    btnRegister = (Button) findViewById(R.id.btnRegister);
    btnLinkToLogin = (Button) findViewById(R.id.btnLinkToLoginScreen);

    // Progress dialog
    pDialog = new ProgressDialog(this);
    pDialog.setCancelable(false);

    // Session manager
    session = new SessionManager(getApplicationContext());

    // SQLite database handler
    db = new SQLiteHandler(getApplicationContext());

    // Check if user is already logged in or not
    if (session.isLoggedIn()) {
        // User is already logged in. Take him to main activity
        Intent intent = new Intent(RegisterActivity.this,
                MainActivity.class);
        startActivity(intent);
        finish();
    }

    // Register Button Click event
    btnRegister.setOnClickListener(new View.OnClickListener() {
        @TargetApi(Build.VERSION_CODES.GINGERBREAD)
        public void onClick(View view) {
            String name = inputFullName.getText().toString();
            String email = inputEmail.getText().toString();
            String password = inputPassword.getText().toString();

      if (!name.isEmpty() && !email.isEmpty() && !password.isEmpty())     {
                registerUser(name, email, password);
            } else {
                Toast.makeText(getApplicationContext(),
                        "Please enter your details!", Toast.LENGTH_LONG)
                        .show();
            }
        }
    });

    // Link to Login Screen
    btnLinkToLogin.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            Intent i = new Intent(getApplicationContext(),
                    LoginActivity.class);
            startActivity(i);
            finish();
        }
    });

     }

  /**
 * Function to store user in MySQL database will post params(tag, name,
 * email, password) to register url
 * */
  private void registerUser(final String name, final String email,
                          final String password) {
    // Tag used to cancel the request
    String tag_string_req = "req_register";

    pDialog.setMessage("Registering ...");
    showDialog();

StringRequest strReq = new    StringRequest(Request.Method.POST,AppConfig.URL_REGISTER, new   Response.Listener<String>() {

        @Override
        public void onResponse(String response) {
            Log.d(TAG, "Register Response: " + response);
            showDialog();

            try {
                JSONObject jObj = new JSONObject(response);
                boolean error = jObj.getBoolean("error");
                if (!error) {
                    // User successfully stored in MySQL
                    // Now store the user in sqlite
                    pDialog.setMessage("Registration Successfull");
                    showDialog();
                    String uid = jObj.getString("uid");

                    JSONObject user = jObj.getJSONObject("user");
                    String name = user.getString("name");
                    String email = user.getString("email");
                    String created_at = user
                            .getString("created_at");

                    // Inserting row in users table
                    db.addUser(name, email, uid, created_at);


                    // Launch login activity
                    Intent intent = new Intent(
                            RegisterActivity.this,
                            LoginActivity.class);
                    startActivity(intent);
                    finish();
                } else {

                    // Error occurred in registration. Get the error
                    // message
                    String errorMsg = jObj.getString("error_msg");
                    Toast.makeText(getApplicationContext(),
                            errorMsg, Toast.LENGTH_LONG).show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e(TAG, "Registration Error: " + error.getMessage());
            Toast.makeText(getApplicationContext(),
                    error.getMessage(), Toast.LENGTH_LONG).show();
            hideDialog();
        }
    }) {

        @Override
        protected Map<String, String> getParams() {
            // Posting params to register url
            Map<String, String> params = new HashMap<String, String>();
            params.put("tag", "register");
            params.put("name", name);
            params.put("email", email);
            params.put("password", password);

            return params;
        }

    };

    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}

private void showDialog() {
    if (!pDialog.isShowing())
        pDialog.show();
}

private void hideDialog() {
    if (pDialog.isShowing())
        pDialog.dismiss();
}
}

What is the problem that's i am facing.Please help me and Thank you in advance :)

Answer 1

First, assure that your php code is returning proper JSON, try simulating an API call by changing your POST vars to GET vars and try the code in your browser. I think that the php code is working, but in your android code, you're requesting StringResponse while you should request a JsonObjectRequest. Try changing that and feedback.