java - Can't Open Fragment when clicked button -

i have created 2 fragment , layout, when click button on profile fragment should open flat layout, force stop application , not opening second fragment, have included fragment code , layout code..

profilefragment.java

public class profilefragment extends fragment { view rootview; @override public view oncreateview(layoutinflater inflater, viewgroup container,                          bundle savedinstancestate) {      rootview = inflater.inflate(r.layout.profile, container, false);      button button = (button) rootview.findviewbyid(r.id.button);     button.setonclicklistener(new view.onclicklistener()     {         @override         public void onclick(view v)         {             onbuttonclicked(v);         }     });     return rootview; } public void onbuttonclicked(view view) {     //do stuff here..     final fragmenttransaction ft = getfragmentmanager().begintransaction();     ft.replace(r.id.button, new flatview(), "newfragmenttag");     ft.commit(); } 

profile.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" tools:context="${packagename}.${activityclass}" android:id="@+id/semester">  <button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="new button"     android:id="@+id/button"     android:layout_centervertical="true"     android:layout_centerhorizontal="true" /> 

flatview.java

public class flatview extends fragment {  @override public view oncreateview(layoutinflater inflater, viewgroup container, bundle savedinstancestate) {     return inflater.inflate(r.layout.flat, container, false); } 

flat.xml

<textview     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:textappearance="?android:attr/textappearancelarge"     android:text="second fragement"     android:id="@+id/textview3"     android:layout_gravity="center_horizontal" /> 

logcat

06-19 07:57:56.945  26457-26457/com.idealdeveloper.saltechnical e/androidruntime﹕ fatal exception: main process: com.idealdeveloper.saltechnical, pid: 26457 java.lang.classcastexception: android.widget.button cannot cast android.view.viewgroup         @ android.support.v4.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:917)         @ android.support.v4.app.fragmentmanagerimpl.movetostate(fragmentmanager.java:1104)         @ android.support.v4.app.backstackrecord.run(backstackrecord.java:682)         @ android.support.v4.app.fragmentmanagerimpl.execpendingactions(fragmentmanager.java:1460)         @ android.support.v4.app.fragmentmanagerimpl$1.run(fragmentmanager.java:440)         @ android.os.handler.handlecallback(handler.java:739)         @ android.os.handler.dispatchmessage(handler.java:95)         @ android.os.looper.loop(looper.java:135)         @ android.app.activitythread.main(activitythread.java:5221)         @ java.lang.reflect.method.invoke(native method)         @ java.lang.reflect.method.invoke(method.java:372)         @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:899)         @ com.android.internal.os.zygoteinit.main(zygoteinit.java:694) 

try guess work

 <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"  tools:context="${packagename}.${activityclass}" android:id="@+id/semester"> <framelayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="new button" android:id="@+id/fragmentlayout" android:layout_centervertical="true" android:layout_centerhorizontal="true" />  <button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="new button" android:id="@+id/button" android:layout_centervertical="true" android:layout_centerhorizontal="true" /> 

class

public class profilefragment extends fragment {   view rootview; @override public view oncreateview(layoutinflater inflater, viewgroup container,                      bundle savedinstancestate) {  rootview = inflater.inflate(r.layout.profile, container, false);  button button = (button) rootview.findviewbyid(r.id.button); button.setonclicklistener(new view.onclicklistener() {     @override     public void onclick(view v)     {         onbuttonclicked(v);     } }); return rootview;  }   public void onbuttonclicked(view view)   {    //do stuff here..    final fragmenttransaction ft = getfragmentmanager().begintransaction();    ft.add(r.id.fragmentlayout, new flatview(), "newfragmenttag");    ft.commit();    } 

i hope 1 helps you