android wrong behavior for listview select/deselect all checkbox action

I have a listView with checkboxes and the first checkbox from list is a select/deselect all checkbox.

List<CheckedItem> items = new ArrayList<CheckedItem>();
   // items.add(new CheckedItem(getResources().getString(R.string.select_all),getResources().getString(R.string.select_all)));
    adapter = new DownloadDocsListViewAdapter(getContext(), items);
    adapter.registerDataSetObserver(new DataSetObserver() {
        @Override
        public void onChanged() {
            SparseBooleanArray sparseArray = adapter.getBooleanArray();
            isAtLeastOneElementChecked = false;
            for(int i = 0; i < sparseArray.size(); i++) {
                int key = sparseArray.keyAt(i);
                // get the object by the key.
                boolean obj = sparseArray.get(key);
                if (i == 0) {
                    for (int j=0; j < listView.getAdapter().getCount(); j++) {
                        CheckedItem checkedItem = (CheckedItem) listView.getAdapter().getItem(i);
                        checkedItem.setChecked(obj);
                    }
                }
                if (obj == true) {
                    isAtLeastOneElementChecked = true;
                    break;
                }
            }

            getActivity().invalidateOptionsMenu();
        }
    });

    listView.setAdapter(adapter);
    listView.setOnItemClickListener(this);
    //add the select All checkbox
    adapter.add(new CheckedItem(getResources().getString(R.string.select_all),getResources().getString(R.string.select_all)));

And this is the adapter of the list

public class DownloadDocsListViewAdapter extends ArrayAdapter<CheckedItem> implements CompoundButton.OnCheckedChangeListener {

    private SparseBooleanArray booleanArray = new SparseBooleanArray();

    public DownloadDocsListViewAdapter(Context context, List<CheckedItem> objects) {
        super(context, R.layout.generated_multiple_docs_item, objects);

        for (CheckedItem checkedItem : objects) {
            objects.add(checkedItem);
        }

    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // Get the data item for this position
        CheckedItem item = getItem(position);    
        // Check if an existing view is being reused, otherwise inflate the view
        if (convertView == null) {
            convertView = LayoutInflater.from(getContext()).inflate(R.layout.download_docs_item, parent, false);
        }

        // Populate the data into the template view using the data object
        TextView tvName = (TextView) convertView.findViewById(R.id.itemTextId);
        tvName.setText(item.getValue());

        CheckBox checkBoxView = (CheckBox) convertView.findViewById(R.id.checkBoxViewId);
        checkBoxView.setOnCheckedChangeListener(this);
        checkBoxView.setTag(position);

        return convertView;
    }

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        int position = Integer.parseInt(buttonView.getTag().toString());
        CheckedItem item = getItem(position);
        booleanArray.put(position, isChecked);
        item.setChecked(isChecked);

        notifyDataSetChanged();
    }

    public SparseBooleanArray getBooleanArray() {
        return booleanArray;
    }
}

The listview checkbox status changed but the listview elements does not appear checked or unchecked.