java - Android activity is returning null through intent -

not sure why keep getting null reference when trying return data main activity activity (done through intents). i've tried serialize everything, , tried other stuff. don't know may causing it. can 1 point out mistake?

here error keep getting:

java.lang.runtimeexception: failure delivering result resultinfo{who=null, request=10, result=0, data=null} activity {ebadly.com.youstreamer/ebadly.com.youstreamer.mainactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'java.io.serializable android.content.intent.getserializableextra(java.lang.string)' on null object reference 

here code in mainactivity class:

public static final int pick_contacts = 10;     public arraylist<contact> msendphonenumbers;     @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);          msendphonenumbers = new arraylist<contact>();         button contactsbutton = (button)findviewbyid(r.id.select_contacts_button);         contactsbutton.setonclicklistener(new view.onclicklistener() {             @override             public void onclick(view v) {                 intent = new intent(mainactivity.this, contactslistactivity.class);                 i.putextra(contactslistactivity.extra, msendphonenumbers);                 startactivityforresult(i, pick_contacts);             }         });          button enterbutton = (button)findviewbyid(r.id.enter_button);         enterbutton.setonclicklistener(new view.onclicklistener() {             @override             public void onclick(view v) {              }         });     } enter code here  @override     protected void onactivityresult(int requestcode, int resultcode, intent data) {         super.onactivityresult(requestcode, resultcode, data);         msendphonenumbers = (arraylist<contact>)data.getserializableextra(contactslistactivity.extra);      } 

here code contactslistactivity class:

protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_contacts_list);          msendphonenumbers = new arraylist<contact>();         msendphonenumbers = (arraylist<contact>) getintent().getserializableextra(extra);          mcontacts = new arraylist<contact>();         cursor phones = getcontentresolver().query(contactscontract.commondatakinds.phone.content_uri, null, null, null, null);         while (phones.movetonext())         {             contact c = new contact();             c.mname = phones.getstring(phones.getcolumnindex(contactscontract.commondatakinds.phone.display_name));             c.mnumber = phones.getstring(phones.getcolumnindex(contactscontract.commondatakinds.phone.number));             mcontacts.add(c);         }         phones.close();          if(!msendphonenumbers.isempty() || msendphonenumbers != null){             for(contact c : msendphonenumbers){                 if(c.mchecked == true){                     for(contact search: mcontacts){                         if(search.mnumber.equals(c.mnumber)){                             search.mchecked = true;                         }                     }                 }             }         }          mcontactslist = (listview) findviewbyid(r.id.contact_list);         mcontactslist.setadapter(new contactlistviewadapter(mcontacts));          mcontactslist.setonitemclicklistener(new adapterview.onitemclicklistener() {             @override             public void onitemclick(adapterview<?> parent, view view, int position, long id) {                 contact c = (contact) parent.getadapter().getitem(position);                 if(c.mchecked == true) c.mchecked = false;                 else c.mchecked = true;             }         });     }  @override     public void onbackpressed(){         super.onbackpressed();         for(contact addcontact: mcontacts){             if (addcontact.mchecked){                 for(contact search : msendphonenumbers){                     if(search.mnumber.equals(addcontact.mnumber)){                         break;                     }else msendphonenumbers.add(addcontact);                 }             }         }         intent = new intent();         log.d("hereee === ", msendphonenumbers.tostring());         i.putextra(extra, msendphonenumbers);         setresult(result_ok, i);         finish();     }