Expandablelistview android with checkbox at onclick select more items

I apologize for my English. I am trying to write a application which use checkbox in ExpandableListView, but, when i click on an item list, the list checked the clicked item and subsequent items with period 6. For example if I click on firt item are checked, in addition to the first, the sixth the twelfth etc. etc. Below there is my code

example

prepareListData();
    expandableListView = (ExpandableListView)findViewById(R.id.expandableListViewProfessioni);
    expandableListAdapterProfessioni = new ExpandableListAdapterProfessioni(this,listDataHeader,listDataProfessioni);

    expandableListView.setAdapter(expandableListAdapterProfessioni);


    expandableListView.setOnGroupClickListener(new OnGroupClickListener() {

        @Override
        public boolean onGroupClick(ExpandableListView parent, View v,
                                    int groupPosition, long id) {
            setListViewHeight(parent, groupPosition);

            return false;
        }
    });


    expandableListView.setOnChildClickListener(new OnChildClickListener() {

        @Override
        public boolean onChildClick(ExpandableListView parent, View v,
                                    int groupPosition, int childPosition, long id) {
            return false;
        }
    });private void prepareListData() {
    listDataHeader = new ArrayList<String>();
    listDataProfessioni = new HashMap<String, ArrayList<Mestieri>>();
    listDataHeader.add("Professione svolta");

    SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
    Gson gson = new Gson();
    String json = sharedPrefs.getString("HomeActivity", null);
    Type type = new TypeToken<ArrayList<Mestieri>>() {}.getType();
    ArrayList<Mestieri> professioni = gson.fromJson(json, type);

    listDataProfessioni.put(listDataHeader.get(0), professioni);
}

private void setListViewHeight(ExpandableListView listView,
                               int group) {
    ExpandableListAdapter listAdapter = (ExpandableListAdapter) listView.getExpandableListAdapter();
    int totalHeight = 0;
    int desiredWidth = View.MeasureSpec.makeMeasureSpec(listView.getWidth(),
            View.MeasureSpec.EXACTLY);
    for (int i = 0; i < listAdapter.getGroupCount(); i++) {
        View groupItem = listAdapter.getGroupView(i, false, null, listView);
        groupItem.measure(desiredWidth, View.MeasureSpec.UNSPECIFIED);

        totalHeight += groupItem.getMeasuredHeight();

        if (((listView.isGroupExpanded(i)) && (i != group))
                || ((!listView.isGroupExpanded(i)) && (i == group))) {
            for (int j = 0; j < listAdapter.getChildrenCount(i); j++) {
                View listItem = listAdapter.getChildView(i, j, false, null,
                        listView);
                listItem.measure(desiredWidth, View.MeasureSpec.UNSPECIFIED);

                totalHeight = 700;

            }
        }
    }

    ViewGroup.LayoutParams params = listView.getLayoutParams();
    int height = totalHeight
            + (listView.getDividerHeight() * (listAdapter.getGroupCount() - 1));
    if (height < 10)
        height = 200;
    params.height = height;
    listView.setLayoutParams(params);
    listView.requestLayout();

}/**************** ADAPTER *******************/public class ExpandableListAdapterProfessioni extends BaseExpandableListAdapter{

private Context _context;
private List<String> _listDataHeader;

public static ArrayList<String> listaProfessioni;

private HashMap<String, ArrayList<Mestieri>> _listDataChild;

public ExpandableListAdapterProfessioni(Context context, List<String> listDataHeader,
                             HashMap<String, ArrayList<Mestieri>> listChildData) {
    this._context = context;
    this._listDataHeader = listDataHeader;
    this._listDataChild = listChildData;
}

@Override
public Object getChild(int groupPosition, int childPosititon) {
    return this._listDataChild.get(this._listDataHeader.get(groupPosition))
            .get(childPosititon).getNome();
}

@Override
public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
}

@Override
public View getChildView(final int groupPosition, final int childPosition,
                         boolean isLastChild, View convertView, ViewGroup parent) {

    final String childText = (String) getChild(groupPosition, childPosition);

    listaProfessioni = new ArrayList<String>();

    if (convertView == null) {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.expandable_listview_item_professioni, null);
    }

    TextView txtListChild = (TextView) convertView
            .findViewById(R.id.expandableListViewProfessioniItem);

    txtListChild.setText(childText);

    final CheckBox checkBox = (CheckBox) convertView.findViewById(R.id.checkBoxItem);

    convertView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if(checkBox.isChecked()){
                checkBox.setChecked(false);

            }else {
                checkBox.setChecked(true);

                //listaProfessioni.add(getChild(groupPosition,childPosition).toString());
            }

        }
    });

    return convertView;
}

@Override
public int getChildrenCount(int groupPosition) {
    return this._listDataChild.get(this._listDataHeader.get(groupPosition))
            .size();
}

@Override
public Object getGroup(int groupPosition) {
    return this._listDataHeader.get(groupPosition);
}

@Override
public int getGroupCount() {
    return this._listDataHeader.size();
}

@Override
public long getGroupId(int groupPosition) {
    return groupPosition;
}

@Override
public View getGroupView(int groupPosition, boolean isExpanded,
                         View convertView, ViewGroup parent) {
    String headerTitle = (String) getGroup(groupPosition);
    if (convertView == null) {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.expandable_listview_professioni, null);
    }

    TextView lblListHeader = (TextView) convertView
            .findViewById(R.id.expandableListViewProfessioniHeader);
    lblListHeader.setTypeface(null, Typeface.NORMAL);
    lblListHeader.setText(headerTitle);

    return convertView;
}

@Override
public boolean hasStableIds() {
    return false;
}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return true;
}}