Volley never returns VolleyError or explains why there is an exception

问题

With the Volley libraries, I extended the Request object to implement GSON serialization. I then extended that new object for how I want to do some of my PUT requests. This is the first object for the GSON serialization:

@Override  
protected Response<t> parseNetworkResponse(NetworkResponse response) {  
    try {  
        String jsonString = new String(response.data, HttpHeaderParser.parseCharset(response.headers)); //response may be too large for string?
        t parsedGSON = mGson.fromJson(jsonString, cls);
        Response <t> returnMessage = Response.success(parsedGSON,  
                HttpHeaderParser.parseIgnoreCacheHeaders(response));
        return returnMessage;

    } catch (UnsupportedEncodingException e) { 
        e.printStackTrace();
        return Response.error(new ParseError(e));  
    } catch (JsonSyntaxException je) {
        je.printStackTrace();
        Log.e("GsonRequest", je.getMessage()!=null?je.getMessage():"JsonSyntaxError");
        return Response.error(new ParseError(je));  
    }  
}

When my network response gets to Response <t> returnMessage = Response.success(parsedGSON, HttpHeaderParser.parseIgnoreCacheHeaders(response)); I have populated <t> objects with the correct classes I passed in completely serialized with all variables and no errors. Yet for some reason Volley jumps to } catch (JsonSyntaxException je) { and I can't reveal the contents of je with debugging breakpoints or printing logs. Also in my extended class:

 new ErrorListener() {
        @SuppressWarnings("unused")
        @Override
        public void onErrorResponse(VolleyError error) {
            error.printStackTrace();

The onErrorResponse is never called (neither is my onResponse section either)

So now I have no idea why Volley is catching a JSONException, when serialization was successful, and I have no idea why Volley isn't returning the Error objects

Insight appreciated

回答1:

The answer is that any Volley function you extend or override must have

    @Override
protected void deliverResponse(T response) {
    // TODO Auto-generated method stub
    mListener.onResponse(response);
}

function implemented. The Listener must be initialized in the constructor and have the onResponse method implemented.

Otherwise your network call will never return in the onResponse section.

EDIT: and your extended Request class has to also implement deliverError, along with deliverResponse

private final Listener<T> mListener;
private ErrorListener mErrorListener;

@Override
 public void deliverError(VolleyError error) {
    mErrorListener.onErrorResponse(error);
}

with ErrorListener initialized in your constructor

回答2:

I have had the same problem this morning. Probably you are not receiving a Json as response, your server is answering with a 200 OK but Volley is waiting for receiving a Json. Than, when it does not receive a Json it generates that error, which has not a HTTP code (because it is not), but is a volley internal error.

You may solve the problem by using the right object (from the volley library) for performing your requests.

If you use a JsonObjectRequest volley needs a JSONObject in the request's body and is aspecting for a JSONObject in the response object. If you use a JsonArrayRequest volley needs a JSONArray in the request and a JSONArray in the response. For each different case you need to extend the JsonRequest class for managing the response.

回答3:

For JSON why don't you use own class for answer, for example:

import com.google.gson.annotations.SerializedName;

public class UserData {
@SerializedName("email")
public String userMail;
@SerializedName("number")
public String number;
@SerializedName("loginName")
public String loginName;
@SerializedName("password")
public String password;

}

and then

public Request<?> getInformation(String loginName, String password, Response.Listener<UserData> responseListener,
                                         Response.ErrorListener errorListener) {

    String url = apiURL;

    Map<String, String> authHeaders = getAuthHeaders(loginName, password);
    authHeaders.put(HEADER_PARAM_INTERFACE_KEY, DPAG_INTERFACE_KEY);
    int method = Request.Method.GET;

    GsonRequest<UserData> request = new GsonRequest<UserData>(
            method,
            url,
            UserData.class,
            authHeaders,
            responseListener,
            errorListener,
            gson);


    return mQueue.add(request);
}

plus here the onResponse and on ErrorResponse

    Application.get().getApi().getInformation(loginName, password,
            new Response.Listener<UserData>() {

                @Override
                public void onResponse(UserData data) {

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


                }
            }
    );

来源：https://stackoverflow.com/questions/21556444/volley-never-returns-volleyerror-or-explains-why-there-is-an-exception

标签

android

android-volley

jsonexception