Question

我需要返回我的ArrayList但是当我调用'volleyReq'时我收到null。请告诉我我做错了什么？当内部有空时如何返回值。我想我应该使用界面，但我不知道如何。谢谢。

 public static ArrayList<KladrObject> volleyReq(String contentType,String limit,String query) {
    final String url = new StringBuilder().append("http://kladr-api.ru/api.php?").append("query=" + query).append("&contentType="+contentType).append("&limit="+limit).append("&token=MY KEY").toString();
    final ArrayList<KladrObject> arr = new ArrayList<KladrObject>();
    final JsonObjectRequest req = new JsonObjectRequest(Request.Method.GET, url,
            new Response.Listener<JSONObject>() {

                @Override
                public void onResponse(JSONObject response) {
                    //JSONArray array = response.getJSONArray("result");
                    try{
                        JSONArray array = response.getJSONArray("result");
                        for (int i = 0;i<array.length();i++) {
                            KladrObject kladrObject = new KladrObject();
                            kladrObject.setName(array.getJSONObject(i).getString("name"));
                            kladrObject.setType(array.getJSONObject(i).getString("type"));
                            kladrObject.setShortype(array.getJSONObject(i).getString("typeShort"));
                            arr.add(kladrObject);


                        }

                    }catch (JSONException e){

                    }


                }

            }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {

            //Do what you want to do on error
        }
    });



    AppController.getInstance().getRequestQueue().add(req);
    return  arr;
}

Answer 1

因为JsonObjectRequest在另一个线程上执行，所以你得到一个null。因此，当方法返回时，arr为空。

要实现您要执行的操作，您可以在需要响应的类中传入Response.Listener和Response.ErrorListener。因此，您的volleyReq方法将如下所示：

  public static void volleyReq(String contentType,String limit,String query, Response.Listener responseListesner, Response.ErrorListener errorListener) 
    {

            final String url = new StringBuilder().append("http://kladr-api.ru/api.php?").append("query=" + query).append("&contentType="+contentType).append("&limit="+limit).append("&token=MY KEY").toString();
            final ArrayList<KladrObject> arr = new ArrayList<KladrObject>();
            final JsonObjectRequest req = new JsonObjectRequest(Request.Method.GET, url,
                   responseListener, errorListener);

    }

您的方法调用将如下所示：

final ArrayList<KladrObject> arr = new ArrayList<KladrObject>();
volleyReq("application/json", 100, "searchQuery", new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    //JSONArray array = response.getJSONArray("result");
                    try{
                        JSONArray array = response.getJSONArray("result");
                        for (int i = 0;i<array.length();i++) {
                            KladrObject kladrObject = new KladrObject();
                            kladrObject.setName(array.getJSONObject(i).getString("name"));
                            kladrObject.setType(array.getJSONObject(i).getString("type"));
                            kladrObject.setShortype(array.getJSONObject(i).getString("typeShort"));
                            arr.add(kladrObject);
                        }

                    }catch (JSONException e){

                    }
                }

            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {

            //Do what you want to do on error
        }
    });

返回值为void

1 个答案: