Как изменять записи в sqlite из ListView?

Таблица sqlite отображается при помощи listView. Как изменить "0" на другое число в нужной ячейке при помощи кнопок + и -?

ListAdapter

    public ArrayList<Cigarettes> MainList;

    public ArrayList<Cigarettes> StudentListTemp;

    public ListAdapter.SubjectDataFilter studentDataFilter;

    public ListAdapter(Context context, int id, ArrayList<Cigarettes> studentArrayList) {

        super(context, id, studentArrayList);

        this.StudentListTemp = new ArrayList<Cigarettes>();

        this.StudentListTemp.addAll(studentArrayList);

        this.MainList = new ArrayList<Cigarettes>();

        this.MainList.addAll(studentArrayList);
    }

    @Override
    public Filter getFilter() {

        if (studentDataFilter == null) {

            studentDataFilter = new ListAdapter.SubjectDataFilter();
        }
        return studentDataFilter;
    }


    public class ViewHolder {

        TextView Name;
        TextView Barcode;
        EditText Quantity;
        Button plus, minus;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ListAdapter.ViewHolder holder = null;

        if (convertView == null) {

            LayoutInflater layoutInflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            convertView = layoutInflater.inflate(R.layout.custom_layout, null);

            holder = new ListAdapter.ViewHolder();

            holder.Name = (TextView) convertView.findViewById(R.id.name);

            holder.Barcode = (TextView) convertView.findViewById(R.id.barcode);

            holder.Quantity = (EditText) convertView.findViewById(R.id.quantity);

            convertView.setTag(holder);

        } else {

            holder = (ListAdapter.ViewHolder) convertView.getTag();
        }

        Cigarettes cigarettes = StudentListTemp.get(position);

        holder.Name.setText(cigarettes.getName());

        holder.Barcode.setText(cigarettes.getBarcode());

        holder.Quantity.setText(cigarettes.getQuantity());

        return convertView;

    }

    private class SubjectDataFilter extends Filter {

        @Override
        protected FilterResults performFiltering(CharSequence charSequence) {

            charSequence = charSequence.toString().toLowerCase();

            FilterResults filterResults = new FilterResults();

            if (charSequence != null && charSequence.toString().length() > 0) {

                ArrayList<Cigarettes> arrayList1 = new ArrayList<Cigarettes>();

                for (int i = 0, l = MainList.size(); i < l; i++) {
                    Cigarettes cigarettes = MainList.get(i);

                    if (cigarettes.toString().toLowerCase().contains(charSequence))

                        arrayList1.add(cigarettes);
                }
                filterResults.count = arrayList1.size();

                filterResults.values = arrayList1;
            } else {
                synchronized (this) {
                    filterResults.values = MainList;

                    filterResults.count = MainList.size();
                }
            }
            return filterResults;
        }

        @SuppressWarnings("unchecked")
        @Override
        protected void publishResults(CharSequence charSequence, FilterResults filterResults) {

            StudentListTemp = (ArrayList<Cigarettes>) filterResults.values;

            notifyDataSetChanged();

            clear();

            for (int i = 0, l = StudentListTemp.size(); i < l; i++)
                add(StudentListTemp.get(i));

            notifyDataSetInvalidated();
        }
    }
} 

Database

    public static final String TABLE_CIG="emp";

    public static final String Table_Column_Name="name";

    public static final String Table_Column_Barcode="barcode";

    public static final String Table_Column_Quantity="quantity";

    public Database(Context context)
    {
        super(context, "GoodsDatabase.db", null, 1);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        String tableEmp="create table "+TABLE_CIG+"("+Table_Column_Name+" TEXT, "+Table_Column_Barcode+" TEXT, "+Table_Column_Quantity+" TEXT)";
        db.execSQL(tableEmp);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    }
    public void insertData(String name, String barcode, String quantity)
    {
        SQLiteDatabase sqLiteDatabase=this.getWritableDatabase();
        ContentValues values=new ContentValues();
        values.put("name",name);
        values.put("barcode",barcode);
        values.put("quantity",quantity);
        sqLiteDatabase.insert("emp",null,values);
    }
    public ArrayList fetchData()
    {
        ArrayList<String>stringArrayList=new ArrayList<String>();
        String fetchdata="select * from emp";
        SQLiteDatabase sqLiteDatabase=this.getReadableDatabase();
        Cursor cursor=sqLiteDatabase.rawQuery(fetchdata, null);
        if(cursor.moveToFirst()){
            do
            {
                stringArrayList.add(cursor.getString(0));
                stringArrayList.add(cursor.getString(1));
                stringArrayList.add(cursor.getString(2));
            } while (cursor.moveToNext());
        }
        return stringArrayList;
    }
}