Button not found when push in Android -

i have problem. have updateactivity button, when click "log out" button, nothing happens. have mainactivity decides view show. here code:

mainactivity.java

public class mainactivity extends fragmentactivitybase { @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     user user = new user();     if(user.getlastuser() == null){         setcontentview(r.layout.activity_main);     }else{         if(user.getlastuser().getactive() == 0) {             setcontentview(r.layout.activity_main);         }else{             setcontentview(r.layout.profile);         }     } } @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.menu_main, menu);     return true; }  @override public boolean onoptionsitemselected(menuitem item) {     // handle action bar item clicks here. action bar     // automatically handle clicks on home/up button, long     // specify parent activity in androidmanifest.xml.     int id = item.getitemid();      //noinspection simplifiableifstatement     if (id == r.id.action_settings) {         return true;     }      return super.onoptionsitemselected(item); } 

}

updateactivity.java

public class updateactivity extends activity {  button logout; @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.profile);     final  intent  intent = new intent(this, mainactivity.class);     logout = (button) findviewbyid(r.id.buttonlogout);      logout.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             fbloginfragment.logout();             user user = new user();             user.disable();             startactivity(intent);         }     }); } 

}

it's never launch update activity. in main activity you're changing layout setcontentview(r.layout.profile); not implementing onclicklistener on button.

you should add onclikclisterner in main activity, or best: should launch updateactivity depending on user status , not changing view of main activity.