使用Facebook Android SDK获取用户数据

Question

我想使用我的应用从Facebook获取用户数据。我编写了代码，它登录用户但无法获取用户数据。这是代码：

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    AccessToken accessToken = AccessToken.getCurrentAccessToken();
    callbackManager = CallbackManager.Factory.create();
    if (PrefUtils.getCurrentUser(getActivity()) != null) {
        //dont ask for login
        Intent homeIntent = new Intent(getActivity(), MainActivity.class);
        startActivity(homeIntent);
        Toast.makeText(getActivity(), "Intent", Toast.LENGTH_SHORT).show();
        //getActivity().finish();
    }

    mCallBack = new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {
            Log.e(TAG, "onSuccess: " );
            // App code
            GraphRequest request = GraphRequest.newMeRequest(loginResult.getAccessToken(), new GraphRequest.GraphJSONObjectCallback() {
                @Override
                public void onCompleted(JSONObject object, GraphResponse response) {
                    Log.e(TAG, "onCompleted: "+object );
                    Log.e("response: ", response + "");
                    try{
                        email = object.getString("email");
                        name = object.getString("name");
                        Toast.makeText(getActivity(), "onSuccess", Toast.LENGTH_SHORT).show();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                    Toast.makeText(getActivity(), "welcome " + user.name+" "+name, Toast.LENGTH_LONG).show();
                    Intent intent=new Intent(getActivity(),MainActivity.class);
                    startActivity(intent);
                    Toast.makeText(getActivity(), "Intent", Toast.LENGTH_SHORT).show();
                    //getActivity().finish();
                }

            });

            Bundle parameters = new Bundle();
            parameters.putString("fields", "id,name,email,gender, birthday");
            request.setParameters(parameters);
            request.executeAsync();

        }

        @Override
        public void onCancel() {
            Log.e(TAG, "onCancel: " );
        }

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

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    rootView = inflater.inflate(R.layout.fragment_sign_in, null);

    mProgressDialog = new ProgressDialog(getActivity());
    mProgressDialog.setCancelable(false);
    skip = (Button) rootView.findViewById(R.id.btn_skip);
    loginButton = (LoginButton) rootView.findViewById(R.id.fb_login_button);

    loginButton.setReadPermissions(Arrays.asList("public_profile", "email", "user_friends"));
    loginButton.setFragment(this);
    btnLogin = (TextView) rootView.findViewById(R.id.btnLogin);
    btnLogin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            loginButton.performClick();
            loginButton.setPressed(true);
            loginButton.invalidate();
            loginButton.registerCallback(callbackManager, mCallBack);
            loginButton.setPressed(false);
            loginButton.invalidate();
            Log.e(TAG, "onClick: ");
        }
    });

    skip.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(Splash.intent);
        }
    });
    return rootView;
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    callbackManager.onActivityResult(requestCode, resultCode, data);
}
}

它记录用户但无法获取数据。在调试时，日志显示为null mCallback。