IllegalStateException

08-04 16:07:21.115  32190-32190/com.example.abhishek.fragmentmodularui E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.IllegalStateException: Fragment FragmentB{41e62678} not attached to Activity
            at android.app.Fragment.getResources(Fragment.java:744)
            at com.example.abhishek.fragmentmodularui.FragmentB.changeData(FragmentB.java:39)
            at com.example.abhishek.fragmentmodularui.MainActivity.respond(MainActivity.java:46)
            at com.example.abhishek.fragmentmodularui.FragmentA.onItemClick(FragmentA.java:43)
            at android.widget.AdapterView.performItemClick(AdapterView.java:301)
            at android.widget.AbsListView.performItemClick(AbsListView.java:1280)
            at android.widget.AbsListView$PerformClick.run(AbsListView.java:3071)
            at android.widget.AbsListView$1.run(AbsListView.java:3973)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4918)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
            at dalvik.system.NativeStart.main(Native Method)