java - NullPointerException : Attempt to read from field 'com. android.volley.Cache$Entry com.android.volley.Response.cacheEntry

Question

我正在使用 Android Volley 从外部 API 获取 JSONArray。我的代码在下面

StringRequest jq = new StringRequest("http://api.example.com/json/States", new Response.Listener<String>() {

        @Override
        public void onResponse(String jsonArray) {
            try {
                Log.d("Success", jsonArray.toString());
            } catch (Exception je) {
                je.printStackTrace();
            }
        }

    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError volleyError) {
            Log.d("Error", volleyError.toString());
        }
    }) {
        @Override
        protected Response parseNetworkResponse(NetworkResponse networkResponse) {
            return null;
        }
    };
    AppController a = AppController.getInstance();
    Log.d("Queue", "Add");
    a.addToRequestQueue(jq);

我一直在下面遇到同样的错误

NetworkDispatcher.run: Unhandled exception java.lang.NullPointerException: Attempt to read from field 'com.android.volley.Cache$Entry com.android.volley.Response.cacheEntry' on a null object reference java.lang.NullPointerException: Attempt to read from field 'com.android.volley.Cache$Entry com.android.volley.Response.cacheEntry' on a null object reference at com.android.volley.NetworkDispatcher.run(NetworkDispatcher.java:126)

我尝试了各种方法。但仍然有同样的问题。我不明白问题出在哪里。帮助解决这个问题

Answer 1

您没有解析响应。您只返回 null 而不是解析缓存 header 。解析响应后，您可以像这样解析带有缓存 header 的响应:

return Response.success(networkResponse, HttpHeaderParser.parseCacheHeaders(networkResponse));

在 parseNetworkResponse(NetworkResponse networkResponse) 方法中返回它