您必须覆盖getBody:

you have to override getBody :

    @Override
public byte[] getBody() throws AuthFailureError {
    return gson.toJson(dataIn).getBytes();
}

整个示例类(形成相同的链接)已

the whole example class(form the same link) edited:

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

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

@Override
public byte[] getBody() throws AuthFailureError {
    return gson.toJson(dataIn).getBytes();
}

@Override
protected Response<T> parseNetworkResponse(NetworkResponse response) {
    try {
        String json = new String(
                response.data,
                HttpHeaderParser.parseCharset(response.headers));
        return Response.success(
                gson.fromJson(json, clazz),
                HttpHeaderParser.parseCacheHeaders(response));
    } catch (UnsupportedEncodingException e) {
        return Response.error(new ParseError(e));
    } catch (JsonSyntaxException e) {
        return Response.error(new ParseError(e));
    }
    }
}