Facebook SDK 3.0 Android-令牌丢失

Question

I'm trying to use the facebook authentification in my app but I'm not able to login because the token is missing. In the LogCat I have a loop : "[Tag]System.out [Text]doLogin:". This happens before the Facebook dialog, and when it appears I click on "Ok" but nothing happens.

Here is my code:

private SharedPreferences.Editor loginPrefsEditor;
private Session.StatusCallback statusCallback = new SessionStatusCallback();


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fb_auth);
    choosePseudoButton = (Button) findViewById(R.id.buttonChoosePseudoFb);
    progressBarFb = (ProgressBar) findViewById(R.id.progressBarFbLoad);
    textViewFbInfo = (TextView) findViewById(R.id.currentInfoFb);
    editTextFbPseudo = (EditText) findViewById(R.id.editTextPseudoFb);
    /*
     * Get existing access_token if any
     */
    mPrefs = getPreferences(MODE_PRIVATE);

    // start Facebook Login
    Session.openActiveSession(this, true, new Session.StatusCallback() {
        public void call(final Session session, SessionState state, Exception exception) {
            if (session.isOpened()) {
                Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {
                    public void onCompleted(GraphUser user, Response response) {
                        if (user != null) {
                            System.out.println("onCreate");  
                            fbToken = session.getAccessToken();
                            SharedPreferences.Editor editor = mPrefs.edit();
                            editor.putString("access_token", fbToken);
                            JSONRequest jr = (JSONRequest) new JSONRequest().execute();

                        }
                    }
                });
            }
            else {
                doLogin();
            }
        }
    });
}

private void doLogin() {
    Session session = Session.getActiveSession();
    if (!session.isOpened() && !session.isClosed()) {
        session.openForRead(new Session.OpenRequest(this).setCallback(statusCallback));
    } else {
        Session.openActiveSession(this, true, statusCallback);
    }
    fbToken = session.getAccessToken();
    System.out.println("doLogin: "+fbToken);
    JSONRequest jr = (JSONRequest) new JSONRequest().execute();
}


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

private void updateView() {
    Session session = Session.getActiveSession();
    if (session.isOpened()) {
        fbToken = session.getAccessToken();
        System.out.println("updateView: "+fbToken);
        JSONRequest jr = (JSONRequest) new JSONRequest().execute();
    } 
    else {
        doLogin();
    }
}

private class SessionStatusCallback implements Session.StatusCallback {
    public void call(Session session, SessionState state, Exception exception) {
        // Respond to session state changes, ex: updating the view
        if( session.isOpened() ){
            Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {

                public void onCompleted(GraphUser user, Response response) {
                }
            });
        }
        updateView();
    }
}

Answer 1

Several things to note:

Session opening happens asynchronously, meaning that when you call Session.openActiveSession, it does not (always) immediately open the session (it has to call into another activity, wait for user input, etc). So your line

fbToken = session.getAccessToken();

will almost always return null.

Secondly, there are a few states a Session can be in before it gets to the OPENED state, so in your SessionStatusCallback, you should probably move the updateView() call to be inside the if(session.isOpened()) check.

Lastly, you're calling Session.openActiveSession in the onCreate method, and in that callback, you're always calling doLogin() if the session is not opened. But like I said before, the session can transition to multiple states before it's OPENED, so you're in fact calling doLogin multiple times. Remove that doLogin() call.