android - Error by starting FragmentActivity -

i want change project activity fragmentactivity. first step create fragment:

public class frag1 extends fragment {      public view oncreateview(layoutinflater inflater, viewgroup container,             bundle savedinstancestate) {         view view = inflater                 .inflate(r.layout.detail_fragment, container, false);         return view;     }  } 

the detail_fragment simple linearlayout textview

the second step (after splashscreen) make parent class fragmentactivity:

public class testfrag extends fragmentactivity {      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.frag_main);     }      @override     public boolean oncreateoptionsmenu(menu menu) {         // inflate menu; adds items action bar if present.         getmenuinflater().inflate(r.menu.activity_main, menu);         return true;     }  } 

the r.layout.frag_main:

<fragment xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/frag"     android:name=".fragments.frag1"     android:layout_width="match_parent"     android:layout_height="match_parent" /> 

on splashscreen know:

intent myint = new intent(this, testfrag.class); startactivity(myint); 

but alwas these errors:

05-18 23:09:51.543: w/dalvikvm(28644): unable resolve superclass of lws/stefma/projectname/testfrag; (20) 05-18 23:09:51.543: w/dalvikvm(28644): link of class 'lws/stefma/projectname/testfrag;' failed 05-18 23:09:51.543: e/dalvikvm(28644): not find class 'ws.stefma.projectname.testfrag', referenced method ws.stefma.projectname.activity_login_registration.oncreate 05-18 23:09:51.543: w/dalvikvm(28644): vfy: unable resolve const-class 94 (lws/stefma/projectname/testfrag;) in lws/stefma/projectname/activity_login_registration; 05-18 23:09:51.543: d/dalvikvm(28644): vfy: replacing opcode 0x1c @ 0x000b 05-18 23:09:51.583: d/androidruntime(28644): shutting down vm 05-18 23:09:51.583: w/dalvikvm(28644): threadid=1: thread exiting uncaught exception (group=0x41850930) 05-18 23:09:51.593: e/androidruntime(28644): fatal exception: main 05-18 23:09:51.593: e/androidruntime(28644): java.lang.noclassdeffounderror: ws.stefma.projectname.testfrag 05-18 23:09:51.593: e/androidruntime(28644):    @ ws.stefma.projectname.activity_login_registration.oncreate(activity_login_registration.java:30) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.activity.performcreate(activity.java:5104) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.instrumentation.callactivityoncreate(instrumentation.java:1080) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.activitythread.performlaunchactivity(activitythread.java:2144) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.activitythread.handlelaunchactivity(activitythread.java:2230) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.activitythread.access$600(activitythread.java:141) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.activitythread$h.handlemessage(activitythread.java:1234) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.os.handler.dispatchmessage(handler.java:99) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.os.looper.loop(looper.java:137) 05-18 23:09:51.593: e/androidruntime(28644):    @ android.app.activitythread.main(activitythread.java:5041) 05-18 23:09:51.593: e/androidruntime(28644):    @ java.lang.reflect.method.invokenative(native method) 05-18 23:09:51.593: e/androidruntime(28644):    @ java.lang.reflect.method.invoke(method.java:511) 05-18 23:09:51.593: e/androidruntime(28644):    @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:793) 05-18 23:09:51.593: e/androidruntime(28644):    @ com.android.internal.os.zygoteinit.main(zygoteinit.java:560) 05-18 23:09:51.593: e/androidruntime(28644):    @ dalvik.system.nativestart.main(native method) 

i have no idea why... confused that: if go fragmentactivity activity runs fine without errors!!!

also have these in androidmanifest:

<activity android:name="ws.stefma.projectname.testfrag" /> 

update:

i have import support-v4 libary. androidmanifest declared minsdk="14" , targetsdk="17". because used support-v4 have imported on fragment-class

import android.app.support.v4.fragment 

now have changed to

import android.app.fragment 

and seems work...

also must change fragmentactivity activity. because fragmentactivity class support v4 package!

update 2 - solution found: here solution

change r.layout.frag_main like:

    <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"         xmlns:tools="http://schemas.android.com/tools"         android:id="@+id/linearlayout1"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:orientation="vertical" >          <fragment            android:id="@+id/fragment1"            android:name="ws.stefma.projectname.frag1"            android:layout_width="match_parent"            android:layout_height="wrap_content" />      </linearlayout>