用android SDK 4.0获取Facebook用户名

这是我的代码不起作用：

protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    FacebookSdk.sdkInitialize(getApplicationContext());
    setContentView(R.layout.activity_firstlogin);

    CallbackManager cm;
    LoginButton     lb;

    cm = CallbackManager.Factory.create();
    lb = (LoginButton) findViewById(R.id.facebook_button);
    Log.d(TAG,"Salut les zouzous");
    LoginManager.getInstance().registerCallback(cm,new FacebookCallback<LoginResult>()
            {
                @Override
                public void onSuccess(LoginResult loginResult)
                {
                   Log.d(TAG,"Success !");
                    Accesstoken tok;
                    tok = Accesstoken.getCurrentAccesstoken();
                    Log.d(TAG,tok.getUserId());
                }

                @Override
                public void onCancel()
                {
                    Log.d(TAG,"On Cancel");
                }

                @Override
                public void onError(FacebookException exception)
                {
                    Log.e(TAG,exception.getMessage());
                }
            });

我确切地知道了

Log.d(TAG," Success");

不打印.

在回调之外只有第一个记录打印内容的日志.

对不起英语不好.