Proses Recyclerview di Main Activity android

public class MainActivity extends AppCompatActivity {

   // link proses yang kalian buat di langkah pertama contoh : http://domainname or ip/folderproses/namaproses
    private static final String data_url = "http://189.128.xx.12/myblogshare/getdata.php";

    RecyclerView mRecyclerView;
    RecyclerView.Adapter mAdapter;
    RecyclerView.LayoutManager mManager;
    ProgressDialog pd;
    ArrayList<ModelData> mItems;

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

        pd = new ProgressDialog(MainActivity.this);
        mRecyclerView = (RecyclerView) findViewById(R.id.list_data);
        mItems = new ArrayList<>();
        mManager = new LinearLayoutManager(MainActivity.this, LinearLayoutManager.VERTICAL, false);
        mRecyclerView.setLayoutManager(mManager);
        mAdapter = new AdapterProcess(MainActivity.this, mItems);
        mRecyclerView.setAdapter(mAdapter);

        loadjson();
    }

    //proses mengambil data
    private void loadjson(){
        pd.setMessage("Mengambil Data");
        pd.setCancelable(false);
        pd.show();

        JsonArrayRequest arrayRequest = new JsonArrayRequest(Request.Method.POST, data_url, null, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {
                pd.cancel();
                Log.d("volley", "response : " + response.toString());
                for (int i=0; i < response.length(); i++){
                    try {
                        JSONObject data = response.getJSONObject(i);
                        ModelData md = new ModelData();
                        md.setNamaData(data.getString("nama_data")); // memanggil nama array yang kita buat
                        mItems.add(md);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
                mAdapter.notifyDataSetChanged();
            }
        }, new Response.ErrorListener(){

            @Override
            public void onErrorResponse(VolleyError error) {
                pd.cancel();
                Log.d("volley", "error : " + error.getMessage());
            }
        });
        Controller.getInstance().addToRequestQueue(arrayRequest);
    }

}