java - media player doesnt work? -

im making kids application code

@override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.hijaiyyah_da);     button btn = (button) findviewbyid(r.id.kembali);     assert btn != null;     btn.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             intent ke_menu = new intent(getapplicationcontext(), taqi.mengaji.mainmenu.class);             ke_menu.addflags(intent.flag_activity_clear_top);             startactivity(ke_menu);         }     });      imagebutton imagebutton = (imagebutton) findviewbyid(r.id.da);      final mediaplayer playbuttonclick = mediaplayer.create(this, r.raw.da);      imagebutton.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view view) {              playbuttonclick.start();           }     });      button butang = (button) findviewbyid(r.id.ke_ro);     butang.setonclicklistener(new view.onclicklistener() {         @override         public void onclick(view v) {             intent ke_dza = new intent(getapplicationcontext(), taqi.mengaji.hijaiyyah_dza.class);             startactivity(ke_dza);         }     }); } 

}

this multiple coded activity classes go b,c,d,e...z. there no error when try simulate when go a,b,c,and d,its plat sound.but wen goes e,it doesnt.i restart when goes e,it plays sound, pattern 5 pages,the sound doesnt play.care explain??