Android：首次使用Facebook SDK 4.1登录时，个人资料信息为NULL

Question

When logging the first time the profile is null and after that it works. Am I using the Profile Tracker and AccessToken Tracker correctly? I am not using Profile.getcurrentprofile() as I was told it will not work. NEW ERROR: When I am logged out of Facebook and I try to login to my android app by pressing the Facebook Login Button the login screen opens but I receive an error:

java.lang.NullPointerException: Attempt to invoke virtual method 'void com.facebook.AccessTokenTracker.stopTracking()' on a null object reference

This question is similar to these questions but the solution does not work and there is no solution provided.

Profile.getCurrentProfile() returns null after logging in (FB API v4.0)

Facebook SDK: Why does Profile.getCurrentProfile() always return null for the first time?

My UPDATED code is below:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    FacebookSdk.sdkInitialize(getActivity().getApplicationContext());

    callbackManager = CallbackManager.Factory.create();

}


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

    final View view = inflater.inflate(R.layout.fragment_main, container, false);


    LoginButton  loginButton = (LoginButton) view.findViewById(R.id.login_button);
    loginButton.setReadPermissions(Arrays.asList("public_profile", "user_friends"));

    // If using in a fragment
    loginButton.setFragment(this);
    // Other app specific specialization

    // Callback registration
    loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
        @Override
        public void onSuccess(LoginResult loginResult) {

            accessTokenTracker = new AccessTokenTracker() {
                @Override
                protected void onCurrentAccessTokenChanged(AccessToken oldAccessToken, AccessToken currentAccessToken) {
                    // Set the access token using
                    // currentAccessToken when it's loaded or set.
                    Profile.fetchProfileForCurrentAccessToken();
                    AccessToken.setCurrentAccessToken(currentAccessToken);

                }
            };

            accessTokenTracker.startTracking();

            profileTracker = new ProfileTracker() {
                @Override
                protected void onCurrentProfileChanged(Profile oldProfile, Profile currentProfile) {
                    // App code
                    if(currentProfile!=null)
                    {
                        Profile.setCurrentProfile(currentProfile);
                        profile = currentProfile;
                    }

                }
            };

            profileTracker.startTracking();

           // App code
            //token you have been granted to access the facebook sever
            AccessToken accessToken = loginResult.getAccessToken();
            //user's profile thats login

            profile = Profile.getCurrentProfile();

            final Bundle extras = new Bundle();

            //error is HERE PROFILE IS NULL
            extras.putString(EXTRA_PROFILENAME, profile.getFirstName());   
            extras.putString(EXTRA_PROFILEID, profile.getId());

            .... rest code
           }

       }



@Override
public void onDestroy() {
    super.onDestroy();
   // accessTokenTracker.stopTracking();
    profileTracker.stopTracking();
}

public void onStop(){
    super.onStop();
    accessTokenTracker.stopTracking();
    profileTracker.stopTracking();
}

Answer 1

You need to put ProfileTokenTracker and AccessTokenTracker in your onSuccess() method and start it there and then stop tracking in onDestroy() or onStop() . That way you start getting data from users profile when he is logged in. This is my onSuccess() method:

 public void onSuccess(LoginResult loginResult) {
        AccessToken accessToken = loginResult.getAccessToken();

        accessTokenTracker = new AccessTokenTracker() {
            @Override
            protected void onCurrentAccessTokenChanged(AccessToken accessToken, AccessToken accessToken1) {

            }
        };
        accessTokenTracker.startTracking();

        profileTracker = new ProfileTracker() {
            @Override
            protected void onCurrentProfileChanged(Profile profile, Profile profile1) {

            }
        };
        profileTracker.startTracking();

        Profile profile = Profile.getCurrentProfile();
        if (profile != null) {
        //get data here
        }
}

Answer 2

Try to move

accessTokenTracker.startTracking();
profileTracker.startTracking();
Profile.fetchProfileForCurrentAccessToken();

into onSuccess() method.