Twitter:send direct message using scribe

Here is my code to send send direct message using scribe. But it gives me null response. What am I doing wrong?

 OAuthRequest req;
 OAuthService s;
 s = new ServiceBuilder()
        .provider(TwitterApi.class)
        .apiKey(APIKEY)
        .apiSecret(APISECRET)
        .callback(CALLBACK)
        .build();
 req = new OAuthRequest(Verb.POST, "https://api.twitter.com/1/direct_messages/new.format?user_id="+user_id+"&text=my app test");

s.signRequest(MyTwitteraccesToken, req);
Response response = req.send();

   if (response.getBody() != null) {
    String t=response.getBody();
    Log.w("twittersent","twittersent"+t);
 }

Can anybody help me ?