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

        private ProgressDialog dialog;
        private ProgressDialog pDialog;
        protected Context applicationContext;
String email,password;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            inputUsername = (EditText) findViewById(R.id.loginUsername);
            inputPassword = (EditText) findViewById(R.id.loginPassword);
             email = inputUsername.getText().toString();
             password = inputPassword.getText().toString();
            pDialog = new ProgressDialog(LoginActivity.this);
            pDialog.setMessage("Loading User ...");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

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


            UserFunctions userFunction = new UserFunctions();
            JSONObject json = userFunction.loginUser(email, password);

            Log.d("Button", "Login");


            return json;

        }

        @Override
        protected void onPostExecute(JSONObject json) {
            // dismiss the dialog after getting all products
            pDialog.dismiss();
                       try {
                if (json.getString(KEY_SUCCESS) != null) {
                    loginErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS);
                    if(Integer.parseInt(res) == 1){
                        // user successfully logged in
                        // Store user details in SQLite Database
                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        // Clear all previous data in database
                        userFunction.logoutUser(getApplicationContext());
                        db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));

                        // Launch Dashboard Screen
                        Intent dashboard = new Intent(getApplicationContext(), DatabaseSample.class);

                        // Close all views before launching Dashboard
                        dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        startActivity(dashboard);

                        // Close Login Screen
                        finish();
                    }else{
                        // Error in login
                        loginErrorMsg.setText("Incorrect username/password");
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
      }