Adding an Fragment id to auto-generated fragment from android studio -

i have created auto generated fragment android studio.

when

tagdatafragment fragment = (tagdatafragment) getsupportfragmentmanager().findfragmentbyid(r.id.tagfragment); fragment.fillvalues(); 

fragment returns null. have googled , found id not added fragment. how , add fragment id .

import android.support.design.widget.tablayout; import android.support.v4.app.fragmenttransaction; import android.support.v7.app.appcompatactivity; import android.support.v7.widget.toolbar;  import android.support.v4.app.fragment; import android.support.v4.app.fragmentmanager; import android.support.v4.app.fragmentpageradapter; import android.support.v4.view.viewpager; import android.os.bundle; import android.view.layoutinflater; import android.view.menu; import android.view.menuitem; import android.view.view; import android.view.viewgroup;  import android.widget.edittext; import android.widget.textview;  public class mainactivity extends appcompatactivity {      /**      * {@link android.support.v4.view.pageradapter} provide      * fragments each of sections. use      * {@link fragmentpageradapter} derivative, keep every      * loaded fragment in memory. if becomes memory intensive,      * may best switch      * {@link android.support.v4.app.fragmentstatepageradapter}.      */     private sectionspageradapter msectionspageradapter;      /**      * {@link viewpager} host section contents.      */     private viewpager mviewpager;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);          toolbar toolbar = (toolbar) findviewbyid(r.id.toolbar);         setsupportactionbar(toolbar);         // create adapter return fragment each of 3         // primary sections of activity.         msectionspageradapter = new sectionspageradapter(getsupportfragmentmanager());          // set viewpager sections adapter.         mviewpager = (viewpager) findviewbyid(r.id.container);         mviewpager.setadapter(msectionspageradapter);          tablayout tablayout = (tablayout) findviewbyid(r.id.tabs);         tablayout.setupwithviewpager(mviewpager);      }       @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) {                tagdatafragment fragment = (tagdatafragment) getsupportfragmentmanager().findfragmentbyid(r.id.tagfragment);             fragment.fillvalues();              return true;          }          return super.onoptionsitemselected(item);     }      public void fillvalues(menuitem item) {     }       /**      * placeholder fragment containing simple view.      */     public static class placeholderfragment extends fragment {         /**          * fragment argument representing section number          * fragment.          */         private static final string arg_section_number = "section_number";          public placeholderfragment() {         }          /**          * returns new instance of fragment given section          * number.          */         public static placeholderfragment newinstance(int sectionnumber) {             placeholderfragment fragment = new placeholderfragment();             bundle args = new bundle();             args.putint(arg_section_number, sectionnumber);             fragment.setarguments(args);             return fragment;         }          @override         public view oncreateview(layoutinflater inflater, viewgroup container,                                  bundle savedinstancestate) {               view rootview = inflater.inflate(r.layout.fragment_main, container, false);             textview textview = (textview) rootview.findviewbyid(r.id.section_label);             textview.settext(getstring(r.string.section_format, getarguments().getint(arg_section_number)));             return rootview;         }     }      /**      * {@link fragmentpageradapter} returns fragment corresponding      * 1 of sections/tabs/pages.      */     public class sectionspageradapter extends fragmentpageradapter {          public sectionspageradapter(fragmentmanager fm) {             super(fm);         }          @override         public fragment getitem(int index) {             // getitem called instantiate fragment given page.             // return placeholderfragment (defined static inner class below).             switch (index) {                 case 0:                      // top rated fragment activity                     return new tagdatafragment();                 case 1:                     // games fragment activity                     return new tagdatafragment();             }              return null;         }          @override         public int getcount() {             // show 3 total pages.             return 2;         }          @override         public charsequence getpagetitle(int position) {               switch (position) {                 case 0:                     return "section 1";                 case 1:                     return "section 2";             }             return null;         }     } }