facebook realtitme update in android returns null

问题

I would like to get realtime_update when user's friendlist changes and am trying to subscribe to friends object .I have the code below where I added params.putString("access_token", "12|wewee"); because I used to get {This method must be called with an app access_token.}, isFromCache:false} .Now I get the response as displayed below.I would like to get realtime subscription .How do I make it work? I really appreciate any help.Thanks in Advance.

code:

Bundle params = new Bundle();
params.putString("object", "user");
params.putString("access_token", "12|wewee");
params.putString("callback_url", "http://example.com/callback/update.php");
params.putString("fields", "friends");
params.putString("verify_token", "1234");
/* make the API call */
new Request(
    session,
    "/12345/subscriptions",
    params,
    HttpMethod.POST,
    new Request.Callback() {
        public void onCompleted(Response response) {
            /* handle the result */
        }
    }
).executeAsync();

Note: session =fb.getsession();

added param to get app_access_tokem:

params.putString("access_token", "12|wewee");

and I get this response :

  {Response:  responseCode: 200, graphObject: GraphObject{graphObjectClass=GraphObject, state={"FACEBOOK_NON_JSON_RESULT":null}}, error: null, isFromCache:false}

来源：https://stackoverflow.com/questions/22957148/facebook-realtitme-update-in-android-returns-null