在json阵列凌空中发送params的最佳方法

Question

我正在使用volley库通过POST请求获取json数组。当我使用get方法时，我能够获取所需的值，但是当我使用POST方法时，我无法获取任何值，而是收到此错误

类型org.json.jsonobject的值无法转换为jsonarray

这是我的代码

 public class xyz extends Activity {

 private static final String url = "http://example.com/q.php";
 private ProgressDialog pDialog;
 private List<Movie> movieList = new ArrayList<Movie>();
 private ListView listView; 
 private CustomListAdapter adapter;

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

listView = (ListView) findViewById(R.id.listview);
adapter = new CustomListAdapter(this, movieList);
listView.setAdapter(adapter);


pDialog = new ProgressDialog(this);
// Showing progress dialog before making http request
pDialog.setMessage("Loading...");
pDialog.show();

// changing action bar color
Response.ErrorListener errorListener = new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError errorResponce)
    {

        VolleyLog.d( "Error: " + errorResponce.getMessage());
        hidePDialog();


    }
};

Response.Listener<JSONArray > jsonArrayListener = new  Response.Listener<JSONArray>()
{
    @Override
    public void onResponse(JSONArray response) {
        // TODO Auto-generated method stub

        hidePDialog();

        // Parsing json
        for (int i = 0; i < response.length(); i++) {
            try {

                JSONObject obj = response.getJSONObject(i);
                Movie movie = new Movie();
                movie.setTitle(obj.getString("ttl"));

                movieList.add(movie);

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

        }

        // notifying list adapter about data changes
        // so that it renders the list view with updated data
        adapter.notifyDataSetChanged();


    }
};
Map<String, String> mParam = new HashMap<String, String>();
mParam.put("q", "ram");

   PostJsonArrayRequest req = new PostJsonArrayRequest(Request.Method.POST, url , null, jsonArrayListener, errorListener,mParam);

// Creating volley request obj

// Adding request to request queue
AppController.getInstance().addToRequestQueue(req);


// Adding request to request queue

}

 @Override
 public void onDestroy() {
super.onDestroy();
hidePDialog();
}

 private void hidePDialog() {
if (pDialog != null) {
    pDialog.dismiss();
    pDialog = null;
}
}


public class PostJsonArrayRequest extends JsonRequest<JSONArray>  {
private Map<String,String> mParam;
private Response.Listener<JSONArray> mListener;
public PostJsonArrayRequest(int method, String url, String requestBody,
                            Response.Listener<JSONArray> listener,  Response.ErrorListener errorListener,Map param) {
    super(method, url, requestBody, listener, errorListener);
    mListener=listener;
    mParam=param;
}

@Override
protected Map<String, String> getParams() throws AuthFailureError {
    return mParam;
}
@Override
protected Response<JSONArray> parseNetworkResponse(NetworkResponse response)       {
    try {
        String jsonString =
                new String(response.data,   HttpHeaderParser.parseCharset(response.headers));
        return Response.success(new JSONArray(jsonString),
                HttpHeaderParser.parseCacheHeaders(response));
    } catch (UnsupportedEncodingException e) {
        return Response.error(new ParseError(e));
    } catch (JSONException je) {
        return Response.error(new ParseError(je));
    }
}
@Override
protected void deliverResponse(JSONArray response) {
    mListener.onResponse(response);

}

}

}

请指导我哪里弄错了。我正确地通过了参数吗？