Can't properly sign out of Facebook on Android with Firebase -

i try logging facebook, it's working. when logged out, facebook's "sign out" button still showing in login activity , when clicked on it, can log out. don't wanna that.

but real question is, how sign out of facebook? i'm using both firebase authentication , facebook authentication(with support firebase)

giris.java (log in)

public class giris extends appcompatactivity implements view.onclicklistener {  private fancybutton buttonsignin; private edittext edittextemail; private edittext edittextpassword; private textview textviewsignup, textviewsifreunuttum, girismesaji; public boolean cancel = false; public boolean isfirststart; private firebaseauth firebaseauth; private firebaseauth.authstatelistener mauthlistener; private dialog progressdialog; private callbackmanager mcallbackmanager; private static final string tag = "facebooklogin";   @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_giris);     facebooksdk.sdkinitialize(getapplicationcontext());     firebaseauth = firebaseauth.getinstance();      mauthlistener = new firebaseauth.authstatelistener() {         @override         public void onauthstatechanged(@nonnull firebaseauth firebaseauth) {             firebaseuser user = firebaseauth.getcurrentuser();             if (user != null) {                 // kullanıcı oturumu açtı                 finish();                 startactivity(new intent(getapplicationcontext(), mainactivity.class));                 log.d("oncreate", "onauthstatechanged:signed_in:" + user.getuid());             } else {                 // kullanıcı oturumu kapattı.                 log.d("oncreate", "onauthstatechanged:signed_out");             }          }     };     firebaseauth.addauthstatelistener(mauthlistener);     mcallbackmanager = callbackmanager.factory.create();     loginbutton loginbutton = (loginbutton) findviewbyid(r.id.login_button);     loginbutton.setreadpermissions("email", "public_profile");     loginbutton.registercallback(mcallbackmanager, new facebookcallback<loginresult>() {         @override         public void onsuccess(loginresult loginresult) {             log.d(tag, "facebook:onsuccess:" + loginresult);             handlefacebookaccesstoken(loginresult.getaccesstoken());         }          @override         public void oncancel() {             log.d(tag, "facebook:oncancel");         }          @override         public void onerror(facebookexception error) {             log.d(tag, "facebook:onerror", error);          }     }); @override protected void onactivityresult(int requestcode, int resultcode, intent  data) {     super.onactivityresult(requestcode, resultcode, data);     mcallbackmanager.onactivityresult(requestcode, resultcode, data); }  private void handlefacebookaccesstoken(accesstoken token) {     log.d(tag, "handlefacebookaccesstoken:" + token);         authcredential credential =          facebookauthprovider.getcredential(token.gettoken());         progressdialog.show();         firebaseauth.signinwithcredential(credential)                 .addoncompletelistener(this, new                    oncompletelistener<authresult>() {                     @override                     public void oncomplete(@nonnull task<authresult> task)                     {                         log.d(tag, "signinwithcredential:oncomplete:" +                          task.issuccessful());                          if(task.issuccessful())                         {                             finish();                             intent fgiris=new intent(giris.this,                              mainactivity.class);                             fgiris.putextra("giris","facebook");                             startactivity(fgiris);                          }                         else                         {                             log.w(tag, "signinwithcredential", task.getexception());                             toast.maketext(giris.this, "facebook ile bağlantı başarız oldu.",                                     toast.length_short).show();                          }                         progressdialog.dismiss();                     }                  });     }     else     {         intent hata = new intent(giris.this, internetcon.class);         startactivity(hata);     } 

mainactivity.java (log out)

public class mainactivity extends appcompatactivity     implements navigationview.onnavigationitemselectedlistener{  private fragment fragment; private fragmentmanager fragmentmanager; public textview tarih; final string prefs_name = "myprefsfile"; final string sharedpref_date = "sharedprefdate"; private firebaseauth firebaseauth; private firebaseuser user; private textview textviewuseremail; public circleimageview userimage;   @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     firebaseauth = firebaseauth.getinstance();     if(firebaseauth.getcurrentuser()==null)     {         finish();         startactivity(new intent(this,giris.class));      }        drawerlayout drawer = (drawerlayout) findviewbyid(r.id.drawer_layout);     final actionbardrawertoggle toggle = new actionbardrawertoggle(             this, drawer, toolbar, r.string.navigation_drawer_open, r.string.navigation_drawer_close);     drawer.setdrawerlistener(toggle);     toggle.syncstate();     navigationview navigationview = (navigationview) findviewbyid(r.id.nav_view);     navigationview.setnavigationitemselectedlistener(this);     view headerview = navigationview.getheaderview(0); //giriste gelen maili navigation header'a @     textviewuseremail= (textview) headerview.findviewbyid(r.id.textkullanicibilgisi);     textviewuseremail.settext(firebaseauth.getcurrentuser().getemail());     userimage= (circleimageview) findviewbyid(r.id.kullanicinavhesapresmi);     fragmentmanager = getsupportfragmentmanager();     fragment = new araclarimfragment();     final fragmenttransaction transaction = fragmentmanager.begintransaction();     transaction.add(r.id.main_container, fragment).commit();   @suppresswarnings("statementwithemptybody") @override public boolean onnavigationitemselected(menuitem item) {     // navigation itemlerinin click olaylarını burada yapıyoruz.     int id = item.getitemid();      if (id == r.id.nav_cikis)     {          intent gelen=getintent();         string logintype=gelen.getstringextra("giris");         if(logintype=="facebook")         {             finish();             firebaseauth.signout();             loginmanager.getinstance().logout();             startactivity(new intent(mainactivity.this, giris.class));         }         else         {             finish();             firebaseauth.getinstance().signout();             startactivity(new intent(mainactivity.this, giris.class));         }     }          drawerlayout drawer = (drawerlayout) findviewbyid(r.id.drawer_layout);         drawer.closedrawer(gravitycompat.start);         return true;  } 

if (id == r.id.nav_cikis)     {          intent gelen=getintent();         string logintype=gelen.getstringextra("giris");         if(logintype=="facebook")         {             firebaseauth.getinstance().signout();             loginmanager.getinstance().logout();             startactivity(new intent(mainactivity.this, giris.class));             finish();         }         else{             firebaseauth.getinstance().signout();             loginmanager.getinstance().logout();             startactivity(new intent(mainactivity.this, giris.class));             finish();// must last line         }