medium.com
Try mFacebook.logout and check reponse value. If logout is successful it will be "true". Works for me. Don't forget about Single Sign-On feature. If you will be still logged in Facebook app it won't really logout you.
stackoverflow.comwww.youtube.com
developers.facebook.com
www.androidtutorialpoint.com
demonuts.com
login-db.com
www.android-examples.com
www.back4app.com
androidclarified.com