java - NullPointerException, can't get my textview from my layout -

edit: answered own question.

my textview null , don't understand why. use personal fragment manager maybe it's problem. id correct because if add fragment on main activity , change text fragment oncreate method change text function works. not work have fragmenta added activity, click on button , count number of time click on it. wanna change textview of fragmentc " counter equal .." , textview null. suspect reason null it's not yet added activity. oncreateview not called. way can fix ? should call fragment.oncreateview in respond function ?

my class textview:

public class fragmentc extends fragment {     textview textview;     @override     public view oncreateview(layoutinflater inflater, @nullable viewgroup container, @nullable bundle savedinstancestate) {         view view = inflater.inflate(r.layout.fragmentc, container,false);         //textview = (textview) view.findviewbyid(r.id.txtinfo2);         return view;     }      @override     public void onactivitycreated(@nullable bundle savedinstancestate) {         super.onactivitycreated(savedinstancestate);         textview = (textview) getactivity().findviewbyid(r.id.txtinfo2);     }      public void changetext(string str){         if(textview==null)             log.e("truc", "null txt");         textview.settext("jghjh");     } } 

log gives txt null

fragmentc.xml

<?xml version="1.0" encoding="utf-8"?> <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"     android:orientation="vertical" android:layout_width="match_parent"     android:layout_height="match_parent"     android:background="#854f98be">      <textview         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="fragment c"         android:id="@+id/txtinfo2"         android:layout_gravity="center_horizontal" /> </linearlayout> 

i put rest of code because have own fragmentmanager , may problem comes there:

my mainactivity:

public class mainactivity extends actionbaractivity implements communicator{      private monfragmentmanager monfragmentmanager;     public static final string tag="truc";      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         monfragmentmanager = new monfragmentmanager                 (getsupportfragmentmanager(),r.id.container,new fragmenta(),new fragmentb(), new fragmentc());         monfragmentmanager.add(1, false);     }     @override public void respond(string data) {     fragmentc frag = (fragmentc) monfragmentmanager.getfragments()[2];     if(frag.getclass()==fragmentc.class)         log.e("truc","fragment correct");         //log gives "fragment correct".     frag.changetext(data); } } 

myownfragmentmanager class:

public class monfragmentmanager {     private fragmentmanager fm;       private fragment[] fragments;     int container;      public monfragmentmanager(fragmentmanager fm){         this.fm = fm;         fragments = fm.getfragments().toarray(new fragment[fm.getfragments().size()]);     }     public monfragmentmanager(fragmentmanager fm, int container,fragment...frags){         this.fm = fm;         this.container=container;         fragments = new fragment[frags.length];         for(int i=0;i<fragments.length;i++){             fragments[i]=frags[i];         }     }      public void hideallfragments(){...}      public void showfragment(int fragmentindex, boolean addtobackstack) {...}     public void add(int fragmentindex, boolean addtobackstack){         fragmenttransaction transaction = fm.begintransaction();          (int = 0; < fragments.length; i++) {             if (i == fragmentindex) {                 transaction.add(container,fragments[i]);             } else if(fragments[i].isadded()) {                 transaction.remove(fragments[i]);             }         }         if (addtobackstack) {             transaction.addtobackstack(null);         }         transaction.commit();     }     public void removeallfragments(){         fragmenttransaction transaction = fm.begintransaction();         for(int = 0; < fragments.length; i++) {             transaction.remove(fragments[i]);         }         transaction.commit();     }     public fragment[] getfragments() {         return fragments;     } } 

it safer findviewbyid() in onviewcreated method.

sample code:

@override public void onviewcreated(view view, bundle savedinstancestate) {     textview = (textview) view.findviewbyid(r.id.txtinfo2); 

notes:

• with onviewcreated, the view parameter supplied, hint.
• i realize you're using onactivitycreated method because triggered after oncreateview. believe upon experience, not documentation, view may not yet ready use. can test behavior rotating screen.