Expandable list with checkbox enabled

[a343]

I'm doing an expandable list in android with checkbox, I did correctly this, but now I'd like that some checkbox appear checked (on true). I did something, but it isn't right becouse the findviewbyid return null. I follow this example http://mylifewithandroid.blogspot.com/2010/02/expandable-lists-and-check-boxes.html

I did it :

private List createChildList() {

ArrayList result = new ArrayList();

// /* each group need each HashMap-Here for each group we have 3
// subgroups */
secList = new ArrayList();
for (UserDetail user : userList) {

HashMap child = new HashMap();
child.put("Sub Item", user.getName());
Log.e(ScrumConstants.TAG, "---- " + user.getName());
chekbox = (CheckBox) findViewById(R.id.check1);
chekbox.toggle()
secList.add(child);
}

Can someone help me?