为什么Volley Custom Request会多次执行

Question

我在代码中使用了android Volley自定义请求， 我面临的问题是，即使请求成功，它也会多次请求服务器

            RequestQueue mRequestQueue = Volley.newRequestQueue(ct);
            JsonRequest sr = new JsonRequest(Request.Method.POST, url,new Response.Listener<JSONObject>() .......);


            int socketTimeout = 10000; //10 seconds - change to what you want
            sr.setRetryPolicy(new DefaultRetryPolicy(socketTimeout, DefaultRetryPolicy.DEFAULT_MAX_RETRIES, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
            mRequestQueue.add(sr);

这里是实作班的班级

class JsonRequest extends Request {

   protected Response.Listener  listener;

    JsonRequest(int method, String url, Response.Listener listener, Response.ErrorListener errorListener)
      {  
        super(method,url,errorListener);
        this.listener = listener;
      }

    //Rest of the code

}