Android EditText giving error on onclick method -

i trying read in contents of w_number_edit_text(a textbox) after login(a button) clicked. on onclick method can't seem access contents of w_number_edit_text. both textbox , button on fragment xml instead of main.xml. can tell me how fix problem. in short how access contents of edittext after button clicked? thank you
code below:

 package com.example.medrec;     import android.support.v7.app.actionbaractivity;     import android.support.v7.app.actionbar;     import android.support.v4.app.fragment;     import android.app.alertdialog;     import android.os.bundle;     import android.view.layoutinflater;     import android.view.menu;     import android.view.menuitem;     import android.view.view;     import android.view.view.onclicklistener;     import android.view.viewgroup;     import android.view.window;     import android.view.windowmanager;     import android.webkit.webview.findlistener;     import android.widget.button;     import android.widget.edittext;     import android.widget.toast;     import android.os.build;      public class mainactivity extends actionbaractivity {      button login;     @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);          setcontentview(r.layout.activity_main);          if (savedinstancestate == null) {             getsupportfragmentmanager().begintransaction()                     .add(r.id.container, new placeholderfragment())                     .commit();         }      }     @override     public boolean oncreateoptionsmenu(menu menu) {          // inflate menu; adds items action bar if present.         getmenuinflater().inflate(r.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();         if (id == r.id.action_settings) {             return true;         }         return super.onoptionsitemselected(item);     }      /**      * placeholder fragment containing simple view.      */     public static class placeholderfragment extends fragment implements onclicklistener{          public placeholderfragment() {         }          @override         public view oncreateview(layoutinflater inflater, viewgroup container,                 bundle savedinstancestate) {             view rootview = inflater.inflate(r.layout.fragment_main, container, false);              button login = (button)rootview.findviewbyid(r.id.w_login);             login.setonclicklistener(this);             return rootview;         }          @override         public void onclick(view v) {             //////////////////////////// problem here             edittext wnumbers =(edittext)findviewbyid(r.id.w_number_edit_text);             string wnumber = wnumbers.gettext().tostring();             toast.maketext(getactivity(), wnumber, toast.length_long).show();          }     }      } 

my activity_main.xml

  <framelayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/container"     android:layout_width="match_parent"     android:layout_height="match_parent"     tools:context="com.example.medrec.mainactivity"     tools:ignore="mergerootframe" /> 

my fragment_main.xml

<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:paddingbottom="@dimen/activity_vertical_margin"     android:paddingleft="@dimen/activity_horizontal_margin"     android:paddingright="@dimen/activity_horizontal_margin"     android:paddingtop="@dimen/activity_vertical_margin"      tools:context="com.example.medrec.mainactivity$placeholderfragment" >      <edittext         android:id="@+id/w_number_edit_text"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_below="@+id/textview1"         android:layout_centerhorizontal="true"         android:layout_margintop="21dp"         android:ems="10"         android:inputtype="number" >          <requestfocus />     </edittext>      <textview         android:id="@+id/textview1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_alignparenttop="true"         android:layout_centerhorizontal="true"         android:layout_margintop="118dp"         android:text="@string/w_number" />      <button         android:id="@+id/w_login"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_below="@+id/w_number_edit_text"         android:layout_centerhorizontal="true"         android:layout_margintop="15dp"         android:text="@string/w_login_text" />  </relativelayout> 

you should change this

 edittext wnumbers =(edittext)findviewbyid(r.id.w_number_edit_text); 

with

edittext wnumbers =(edittext)rootview.findviewbyid(r.id.w_number_edit_text); 

and oncreateview(......) below:

 edittext wnumbers  @override     public view oncreateview(layoutinflater inflater, viewgroup container,             bundle savedinstancestate) {         view rootview = inflater.inflate(r.layout.fragment_main, container, false);          button login = (button)rootview.findviewbyid(r.id.w_login);         wnumbers =(edittext)rootview.findviewbyid(r.id.w_number_edit_text);         login.setonclicklistener(new onclicklistener(){      @override     public void onclick(view arg0) {         // todo auto-generated method stub      string wnumber = wnumbers.gettext().tostring();     toast.maketext(getactivity(), wnumber, toast.length_long).show();        }      });         return rootview;     }