problems with my codes = retrieving datas from mySQL

public class UpdateDeleteData extends AppCompatActivity {

    EditText item_name_et;
    String id, item_name;

    ProgressDialog PD;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update_delete_data);

        PD = new ProgressDialog(this);
        PD.setMessage("please wait.....");
        PD.setCancelable(false);

        item_name_et = (EditText) findViewById(R.id.modify_item_et);
        Intent i = getIntent();

        HashMap<String, String> item = (HashMap<String, String>) i
                .getSerializableExtra("item");

        id = item.get(ReadData.ITEM_ID);
        item_name = item.get(ReadData.ITEM_NAME);

        item_name_et.setText(item_name);

    }

    public void update(View view) {
        PD.show();
        item_name = item_name_et.getText().toString();


        Map<String, String> params = new HashMap<String, String>();
        params.put("id", id);
        params.put("item_name",item_name);

        CustomRequest update_request = new CustomRequest(Request.Method.POST, AppConfig.URL_UPDATE_GRP, params, new Response.Listener<JSONObject>() {

            @Override
            public void onResponse(JSONObject response) {

                try{
                    int success = response.getInt("success");

                    if (success == 1) {
                        PD.dismiss();
                        Toast.makeText(getApplicationContext(),
                                "Updated Successfully",
                                Toast.LENGTH_SHORT).show();
                        // redirect to readdata
                        MoveToReadData();

                    } else {
                        PD.dismiss();
                        Toast.makeText(getApplicationContext(),
                                "failed to update", Toast.LENGTH_SHORT)
                                .show();
                    }
                }
                catch (Exception e){
                    PD.dismiss();
                }

            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError response) {
                PD.dismiss();
            }
        });


        // Adding request to request queue
        MyApplication.getInstance().addToReqQueue(update_request);
    }


    public void delete(View view) {
        PD.show();


// start of error

        JsonObjectRequest delete_request = new JsonObjectRequest(AppConfig.URL_DELETE_GRP + id,
                new Response.Listener<JSONObject>() {

                    @Override
                    public void onResponse(JSONObject response) {

                        try {
                            int success = response.getInt("success");

                            if (success == 1) {
                                PD.dismiss();
                                Toast.makeText(getApplicationContext(),
                                        "Deleted Successfully",
                                        Toast.LENGTH_SHORT).show();
                                // redirect to readdata
                                MoveToReadData();
                            } else {
                                PD.dismiss();
                                Toast.makeText(getApplicationContext(),
                                        "failed to delete", Toast.LENGTH_SHORT)
                                        .show();
                            }

                        } catch (JSONException e) {
                            e.printStackTrace();
                        }

                    }
                }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {

            }
        }); 
//end of error

        // Adding request to request queue
        MyApplication.getInstance().addToReqQueue(delete_request);

    }

    private void MoveToReadData() {
        Intent read_intent = new Intent(UpdateDeleteData.this, ReadData.class)
                .setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

        startActivity(read_intent);

    }
}