Question

服务器返回以下JSON -

[ { ＆＃34; user_id＆＃34;：1，＆＃34; first_name＆＃34;：＆＃34; alex＆＃34;，＆＃34; last_name＆＃34;：＆＃34; goft＆＃34;，＆＃34;密码＆＃34;：＆＃34; doom00＆＃34;，＆＃34;电子邮件＆＃34;：＆＃34; alex@mail.com"，＆＃34;用户名＆＃34;：＆＃34; alexgoft＆＃34; } ]

我正在尝试使用以下函数使用volley来检索它 -

public void makeRequest() {
        final String HOST = "http://10.0.2.2:3000/";
        final String url = HOST + "get_data?type=user&username=alexgoft";
        RequestQueue queue = Volley.newRequestQueue(context);

        Toast.makeText(context, url, Toast.LENGTH_LONG).show();

        // prepare the Request
        JsonObjectRequest getRequest = new JsonObjectRequest(Request.Method.GET, url,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Toast.makeText(context, "In succ", Toast.LENGTH_LONG).show();
                        try {
                            returned_json = response.getJSONObject(0);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(context, "In error", Toast.LENGTH_LONG).show();
                        Toast.makeText(context, error.toString(), Toast.LENGTH_LONG).show();
                        error.getStackTrace();
                        Log.d("error", error.toString());
                    }
                });

        queue.add(getRequest);
    }

问题是我收到以下错误 -

Error:(46, 40) error: no suitable constructor found for JsonObjectRequest(int,String,<anonymous Listener<JSONArray>>,<anonymous ErrorListener>)
constructor JsonObjectRequest.JsonObjectRequest(int,String,Listener<JSONObject>,ErrorListener) is not applicable
(argument mismatch; <anonymous Listener<JSONArray>> cannot be converted to Listener<JSONObject>)
constructor JsonObjectRequest.JsonObjectRequest(String,JSONObject,Listener<JSONObject>,ErrorListener) is not applicable
(argument mismatch; int cannot be converted to String)

我需要做什么才能使returned_json包含来自主机的返回json？

这就是它在ide中的样子 -

Answer 1

如果您没有任何数据可以传递请求，则需要传递null

注意：由于您的回复是JSONArray，因此您需要实施JsonArrayRequest而不是JsonObjectRequest @Krupa Kakkad

new JsonObjectRequest(Request.Method.GET, url, null,
//                                            ^^^^
                new Response.Listener<JSONArray>() {

From Docs

@param jsonRequest A {@link JSONObject} to post with the request. Null is allowed and
     *   indicates no parameters will be posted along with request.

构造函数签名

public JsonObjectRequest（int method，String url，JSONObject jsonRequest，侦听器侦听器，ErrorListener errorListener）{

或

public JsonObjectRequest（String url，JSONObject jsonRequest，听众听众， ErrorListener errorListener）{

Answer 2

您必须致电JsonArrayRequest而不是JsonObjectRequest。

供参考：https://www.androidhive.info/2014/09/android-json-parsing-using-volley/

使用volley时，找不到适合JsonObjectRequest错误的构造函数

2 个答案: