how to parse android volley gson request to a list / collection of objects

Question

I am trying to make a Gson request using android volley. Currently it it working correctly and I am very happy. However why I try and get a List<> or a collection of obje

Answer 1

I recently needed to implement a solution myself so here you go. Custom GsonArrayRequest.

public class GsonArrayRequest<T> extends Request<ArrayList<T>> {
     private final Gson gson = new Gson();
     private final Class<T> clazz;
     private final Map<String, String> headers;
     private final Response.Listener<ArrayList<T>> listener;

    /**
     * Make a GET request and return a parsed object from JSON.
     * @param clazz Relevant class object, for Gson's reflection
     * @param url     URL of the request to make
     * @param headers Map of request headers
     */
     public GsonArrayRequest(String url, Class<T> clazz, Map<String, String> headers,
                        Response.Listener<ArrayList<T>> listener, Response.ErrorListener errorListener) {
    super(Method.GET, url, errorListener);
    this.clazz = clazz;
    this.headers = headers;
    this.listener = listener;
}

@Override
public Map<String, String> getHeaders() throws AuthFailureError {
    return headers != null ? headers : super.getHeaders();
}

@Override
protected Response<ArrayList<T>> parseNetworkResponse(NetworkResponse response) {
    try {
        String json = new String(
                response.data,
                HttpHeaderParser.parseCharset(response.headers));

        Type listType = com.google.gson.internal.$Gson$Types.newParameterizedTypeWithOwner(null, ArrayList.class, clazz);
        ArrayList<T> tList = gson.fromJson(json, listType);
        return Response.success(
                tList,
                HttpHeaderParser.parseCacheHeaders(response));
    } catch (UnsupportedEncodingException e) {
        return Response.error(new ParseError(e));
    } catch (JsonSyntaxException e) {
        return Response.error(new ParseError(e));
    }
}

     @Override
     protected void deliverResponse(ArrayList<T> response) {
         listener.onResponse(response);
     }
 }

You can use it like this:

GsonArrayRequest<StoreWorkout> gsonArrayRequest = new GsonArrayRequest<>(
        url, AngryPugs.class, null, new Response.Listener<ArrayList<AngryPugs>>() {
    @Override
    public void onResponse(ArrayList<AngryPugs> response) {
        // your list here
    }
}, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {

    }
});

After adding the request

 VolleySingleton.getInstance(this).addToRequestQueue(gsonArrayRequest);

Answer 2

Use YourClass[] for List of objects in Volley request. It has solved my issue. The following code should help you:

GsonRequest<ReviewModel[]> jsObjRequest = new GsonRequest<ReviewModel[]>(Request.Method.GET,
        url, ReviewModel[].class, new Response.Listener<ReviewModel[]>() {
            @Override
            public void onResponse(ReviewModel[] response) {
                ReviewsHandleOkResponse(response);
            }
        }, new ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                ReviewsHandleErrorResponse(error);
            }
        });
Network.getInstance(getActivity()).addToRequestQueue(jsObjRequest);
}