Question

When the user revokes the app permission through facebook, this code should ask the user to re-authorize, however it isn’t. Can anyone see something wrong? “facebook” is a Facebook object.

public void facebookSetup() {
    mPrefs = getPreferences(MODE_PRIVATE);
    String access_token = mPrefs.getString("access_token", null);   //load an access token from sharedPreferences
    long expires = mPrefs.getLong("access_expires", 0);     //do the same for the token expiration time

    if (access_token != null) { //if the access token exists in sharedPreferences, we'll use it
        facebook.setAccessToken(access_token);
    }
    if (expires != 0) { //if the expiration time exists in shared preferences, use it
        facebook.setAccessExpires(expires);
    }

    if (!facebook.isSessionValid()) {
        facebook.authorize(this, new String[] { "email", "publish_stream", "user_photos", "publish_actions"}, new DialogListener() {
            @Override
            public void onComplete(Bundle values) {
                SharedPreferences.Editor editor = mPrefs.edit();
                editor.putString("access_token", facebook.getAccessToken());
                editor.putLong("access_expires", facebook.getAccessExpires());
                editor.commit();
            }
            @Override
            public void onFacebookError(FacebookError error) {}

            @Override
            public void onError(DialogError e) {}

            @Override
            public void onCancel() {}
        });
    } 
}

Answer 1

This is what Facebook SDK docs say:

You may detect access token errors by inspecting the response
parameter of the onComplete method. In this case, you will again need
to call facebook.authorize() to re-authenticate the user and generate
a fresh access token.

You need to check response of your Facebook calls to detect such sitautuons. E.g.:

JSONObject responseJSON = new JSONObject(response);
JSONObject errorJSON = responseJSON.optJSONObject("error");
if (errorJSON!=null) {
    String error =errorJSON.optString("type");           
    if (error!=null && error.equals("OAuthException")) {    
        facebook.authorize(activity, FACEBOOK_PERMISSIONS, facebookDialogListener); 
        return; 
    }       
}