public String getSortConfig() {
		StringBuilder buffer = new StringBuilder();
		int count = mColumns.size();
		boolean hasSort = false;

		buffer.append('S');
		buffer.append(CONFIG_VERSION);
		buffer.append('\t');
		buffer.append(count);
		for (int i = 0; i < count; i++) {
			Column column = getColumnAtIndex(i);
			int sequence = column.getSortSequence();

			buffer.append('\t');
			buffer.append(column.getID());
			buffer.append('\t');
			buffer.append(sequence);
			buffer.append('\t');
			buffer.append(column.isSortAscending());
			if (sequence > -1) {
				hasSort = true;
			}
		}

		return hasSort ? buffer.toString() : null;
	}