Hi, i am trying to authenticate something(in this case LinkedIn) using OAuth but the requested token always returns null?

Here is my code below:

public void authenticateAppOauthApi() {
        Log.d(TAG, "authenticateAppOauthApi");

        OAuthServiceProvider provider = new OAuthServiceProvider(
                REQUEST_TOKEN_PATH, AUTHORIZE_PATH, ACCESS_TOKEN_PATH);

        OAuthConsumer consumer = new OAuthConsumer(CALLBACK_URL, API_KEY,
                SECRET_KEY, provider);

        OAuthAccessor accessor = new OAuthAccessor(consumer);

        Intent intent = new Intent(Intent.ACTION_VIEW);
        Log.d(TAG, "Intent intent = new Intent(Intent.ACTION_VIEW );");
        // intent.setData(Uri.parse(url));
        String url = accessor.consumer.serviceProvider.userAuthorizationURL
                + "?oauth_token=" + accessor.requestToken + "&oauth_callback="
                + accessor.consumer.callbackURL;

        intent.setData(Uri.parse(url));
        Log.d(TAG, "intent.setData(Uri.parse(url)); = " + url);
        mContext.startActivity(intent);

        Log.d(TAG, "finish authenticateApp");
}

I basicaly followed the example here http://donpark.org/blog/2009/01/24/android-client-side-oauth

thanks in advance