Below is my code for base adapter. I will be using this class as an adapter for a ListView.
public class CustombaseAdapterTxnCartSelect extends BaseAdapter
{
    private Context mContext;
    private List<RowItemTxnCartSelect> mRowItems;
    TextView standDesc, seats, totalTicketTariff, eventDesc;
    public CustombaseAdapterTxnCartSelect(Context context, List<RowItemTxnCartSelect> rowItems) {
        mContext = context;
        mRowItems = rowItems;       
    }
    @Override
    public int getCount() {
        return mRowItems.size();
    }
    @Override
    public Object getItem(int position) {
        return mRowItems.get(position);
    }
    @Override
    public long getItemId(int position) {
        return mRowItems.indexOf(getItem(position));
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        convertView = null;
        LayoutInflater mInflator = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = mInflator.inflate(R.layout.event_layout_txn__cart_select, null);
        standDesc = (TextView) convertView.findViewById(R.id.textViewTxnCartSelectStandDesc);
        seats = (TextView) convertView.findViewById(R.id.textViewTxnCartSelectSeats);
        totalTicketTariff = (TextView) convertView.findViewById(R.id.textViewTxnCartSelectTotalTicketTariff);
        eventDesc = (TextView) convertView.findViewById(R.id.textViewEventDesc);
        RowItemTxnCartSelect row = (RowItemTxnCartSelect) getItem(position);
        standDesc.setText(row.getmStandDesc());
        seats.setText(row.getmSeats());
        totalTicketTariff.setText(row.getMtotalTicketTariff());
        eventDesc.setText(row.getmEventDesc());
        return convertView;
    }
}
I just want to convert it into an expandable list view I'm not clear about what all I have to add.