java - Android RecyclerViewer throws an exception -

i using volley library on android project, have been struggling code while. have experienced can shed light if can.

logcat

java.lang.runtimeexception: unable start activity componentinfo{com.example.grafiq.testviewapp/com.example.grafiq.testviewapp.mainactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'void android.support.v7.widget.recyclerview.sethasfixedsize(boolean)' on null object reference         @ android.app.activitythread.performlaunchactivity(activitythread.java:2694) 

mainactivity.java oncreate

   protected void oncreate(bundle savedinstancestate) {      super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_main);     openactivity = (button)findviewbyid(r.id.btn_child);     myrecyclerview = (recyclerview)findviewbyid(r.id.myrecycleview);     myrecyclerview.setlayoutmanager(new linearlayoutmanager(this));       //request que     requestqueue myrequest = volleysingleton.getinstance().getrequestque();      //jsonobjectrequest     jsonobjectrequest myjsonreq = new jsonobjectrequest(request.method.get, myurl, null, new response.listener<jsonobject>(){          @override         public void onresponse(jsonobject jsonobject) {             toast.maketext(mainactivity.this, "json-response "+jsonobject.tostring() ,toast.length_long).show();              adapter = new myadapter(mainactivity.this, poparray(jsonobject));             myrecyclerview.setadapter(adapter);         }     }, new response.errorlistener(){          @override         public void onerrorresponse(volleyerror volleyerror) {             toast.maketext(mainactivity.this, "response "+volleyerror.getmessage() ,toast.length_long).show();         }     });      myrequest.add(myjsonreq);   }