SetText NullPointerException for ArrayList in PopupWindow. Android -

i want display array in textview popup window. 1 item array randomly. in case using arraylist in mainactivity , calling randomarray() display. not work on screen_popup.xml. work in main_activity.xml. using textview textview1 main_activity & textview txtviewarraycontent popup window. think textview initialized correctly has setcontentview? pointers great, thank you!

the error in log cat is:

07-17 09:25:34.655  25779-25779/com.example.testarray_02 e/androidruntime﹕ fatal exception: main process: com.example.testarray_02, pid: 25779 java.lang.runtimeexception: unable start activity componentinfo{com.example.testarray_02/com.example.testarray_02.mainactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'void android.widget.textview.settext(java.lang.charsequence)' on null object reference 

main activity java:

public class mainactivity extends activity {  button btnclosepopup; button btncreatepopup; textview newarray; string item;  //***** random generator & arraylist ***** final random randomgenerator = new random(); final arraylist sample = new arraylist() {{ add("random facts stuff"); add("random facts stuff 2"); add("random facts stuff 3"); add("random facts stuff 4");}};  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     //works - main activity layout    // newarray = (textview)findviewbyid(r.id.textview1);      // not work. ... popup layout     newarray = (textview)findviewbyid(r.id.txtviewarraycontent);      randomarray();     btncreatepopup = (button) findviewbyid(r.id.button1);     btncreatepopup.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {              custompopupwindow(v);         }     }); }  private void randomarray() {     //setcontentview(r.layout.screen_popup);     item = (string) sample.get(randomgenerator.nextint(sample.size()));     newarray.settext(item);  // error logcat points line                              // null exception error } private popupwindow popupwin; private void custompopupwindow(view v){     try {         layoutinflater inflater = (layoutinflater) mainactivity.this                 .getsystemservice(context.layout_inflater_service);         view layout = inflater.inflate(r.layout.screen_popup,                 (viewgroup) findviewbyid(r.id.popup_element));         popupwin = new popupwindow(layout, 600, 600, true);         popupwin.showatlocation(layout, gravity.center, 0, 0);         btnclosepopup = (button) layout.findviewbyid(r.id.btn_close_popup);         btnclosepopup.setonclicklistener(cancel_button_click_listener);     } catch (exception e) {         e.printstacktrace();     } } private view.onclicklistener cancel_button_click_listener = new view.onclicklistener() {     public void onclick(view v) {         popupwin.dismiss();     } }; } 

snippet of xml screen popupwindow

    <textview     android:id="@+id/txtviewarraycontent"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_margintop="5sp"     android:text="" /> 

you trying initialize newarray trying find id in activity_main.xml file, it's not there, nullpointerexception. fix code, remove newarray initialization , call of randomarray() oncreate() method , add in custompopupwindwo(view v) follows:

private void custompopupwindow(view v) {     layoutinflater inflater = (layoutinflater) mainactivity.this             .getsystemservice(context.layout_inflater_service);     view layout = inflater.inflate(r.layout.screen_popup,             (viewgroup) findviewbyid(r.id.popup_element));     newarray = (textview) layout.findviewbyid(r.id.txtviewarraycontent);     //omitted rest brevity }