고수님들 간단한 변수 문제인데 좀 도와주십시오ㅠㅠ

Question

코드에서 mArrayList변수가 안바뀝니다ㅠㅠ 매서드 안에서는 바뀌는데 그후에 다시 변하기 전 값으로 돌아옵니다.ㅠㅠ 도와주세요 행님덜 Getdata클래스 안에서는 바뀝니다ㅠㅜㅠㅜㅠ

package com.example.maptest;

import android.support.v7.app.AppCompatActivity;

import android.app.FragmentManager;
import android.app.ProgressDialog;
import android.content.Intent;
import android.location.Address;
import android.location.Geocoder;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
import android.widget.Toast;

import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapFragment;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.model.LatLng;
import com.google.maps.android.clustering.ClusterManager;

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

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

public class MainActivity extends AppCompatActivity implements OnMapReadyCallback {


    private static String TAG = "searchtest";

    private static final String TAG_JSON = "webnautes";
    private static final String TAG_NUMBER = "number";
    private static final String TAG_NAME = "name";
    private static final String TAG_ADDRESS = "address";

    ArrayList<HashMap<String, String>> mArrayList = new ArrayList<>();

    String mJsonString;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        GetData task = new GetData();
        task.execute("http://172.16.107.197/phptest.php");


        FragmentManager fragmentManager = getFragmentManager();
        MapFragment mapFragment = (MapFragment) fragmentManager
                .findFragmentById(R.id.fragment);
        mapFragment.getMapAsync(this);

    }


    public void onMapReady(GoogleMap googleMap) {

        GetData task = new GetData();
        task.execute("http://172.16.107.197/phptest.php");
        ClusterManager<Item> clusterManager = new ClusterManager<Item>(this, googleMap);

        LatLng center = new LatLng(37.52487, 126.92723);
        googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(center, 15));
//        for (int i = 0; i < mArrayList.size(); i++) {
//            HashMap<String, String> hashMap = mArrayList.get(i);
//            String name = hashMap.get(TAG_NAME);
//            String address = hashMap.get(TAG_ADDRESS);
//            String number = hashMap.get(TAG_NUMBER);
//            LatLng latlng = search(address);
//            clusterManager.addItem(new Item(latlng, name, address));
//        }
    }

    public LatLng search(String address) {
        Geocoder coder = new Geocoder(new MainActivity());
        LatLng latlng = null;
        String infoAddr = "";
        try {
            List<Address> addrList = coder.getFromLocationName(address, 3);
            Iterator<Address> addrs = addrList.iterator();


            while (addrs.hasNext()) {
                Address loc = addrs.next();
                double lat = loc.getLatitude();
                double lng = loc.getLongitude();
                latlng = new LatLng(lat, lng);
            }

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


    private class GetData extends AsyncTask<String, Void, String> {
        ProgressDialog progressDialog;
        String errorString = null;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            progressDialog = ProgressDialog.show(MainActivity.this,
                    "기다려 유열", null, true, true);
        }


        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);


            progressDialog.dismiss();
            Log.d(TAG, "response  - " + result);

            if (result == null) {

            } else {

                mJsonString = result;
                showResult();
            }
        }


        @Override
        protected String doInBackground(String... params) {

            String serverURL = params[0];


            try {

                URL url = new URL(serverURL);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();


                httpURLConnection.setReadTimeout(5000);
                httpURLConnection.setConnectTimeout(5000);
                httpURLConnection.connect();


                int responseStatusCode = httpURLConnection.getResponseCode();
                Log.d(TAG, "response code - " + responseStatusCode);

                InputStream inputStream;
                if (responseStatusCode == HttpURLConnection.HTTP_OK) {
                    inputStream = httpURLConnection.getInputStream();
                } else {
                    inputStream = httpURLConnection.getErrorStream();
                }


                InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);

                StringBuilder sb = new StringBuilder();
                String line;

                while ((line = bufferedReader.readLine()) != null) {
                    sb.append(line);
                }


                bufferedReader.close();


                return sb.toString().trim();


            } catch (Exception e) {

                Log.d(TAG, "InsertData: Error ", e);
                errorString = e.toString();

                return null;
            }

        }


        private void showResult() {
            try {
                JSONObject jsonObject = new JSONObject(mJsonString);
                JSONArray jsonArray = jsonObject.getJSONArray(TAG_JSON);

                for (int i = 0; i < jsonArray.length(); i++) {

                    JSONObject item = jsonArray.getJSONObject(0);

                    String number = item.getString(TAG_NUMBER);
                    String name = item.getString(TAG_NAME);
                    String address = item.getString(TAG_ADDRESS);

                    HashMap<String, String> hashMap = new HashMap<>();

                    hashMap.put(TAG_NUMBER, number);
                    hashMap.put(TAG_NAME, name);
                    hashMap.put(TAG_ADDRESS, address);


                    mArrayList.add(hashMap);
                }



            } catch (JSONException e) {

                Log.d(TAG, "showResult : ", e);
            }

        }
    }
}