Android get checked checkbox items in listview -

Android get checked checkbox items in listview -

i have simple checkbox items list view , want checked items clicking on button. unfortunally error , can not debug application.

fatal exception: main java.lang.nullpointerexception

this error line:

if(sparsebooleanarray.get(i) == true)

my code checked items listview:

public class contactlistactivity extends activity{ . . . lv = (listview) findviewbyid(r.id.lv); bt_send_group = (button) findviewbyid(r.id.bt_send_group); contact_item = new arraylist<contactliststructure>(); /* attach listview array adapter */ contactsadapter = new adaptersendsms(contact_item); lv.setadapter(contactsadapter); /* load contacts photos phone , reload listview */ thread threadtask = new thread() { @override public void run() { getnumber(getcontentresolver()); runonuithread(new runnable() { @override public void run() { contactsadapter.notifydatasetchanged(); } }); } }; threadtask.start(); bt_send_group.setonclicklistener(new view.onclicklistener() { @override public void onclick(view v) { int cntchoice = lv.getcount(); string checked = ""; string unchecked = ""; sparsebooleanarray sparsebooleanarray = lv.getcheckeditempositions(); for(int = 0; < cntchoice; i++) { if(sparsebooleanarray.get(i) == true) { checked += lv.getitematposition(i).tostring() + "\n"; } else if(sparsebooleanarray.get(i) == false) { unchecked+= lv.getitematposition(i).tostring() + "\n"; } } } }); . . . }

android listview