Bug 128317 group header and footer checkboxes
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/GroupDialog.java
}
	public void elementChanged( DesignElementHandle focus, NotificationEvent ev )
	{
		if ( ev instanceof PropertyEvent )
		{
			if ( GroupHandle.BOUND_DATA_COLUMNS_PROP.equals( ( (PropertyEvent) ev ).getPropertyName( ) ) )
			{
				refreshColumnList( );
			}
		}
	}
	public boolean close( )
	{
		inputGroup.removeListener( this );
		return super.close( );
	}
	private String getKeyExpression( )
	{
		String exp = null;
		if ( keyChooser.getSelectionIndex( ) != -1 )
		{
			exp = DEUtil.getExpression( columnList.get( keyChooser.getSelectionIndex( ) ) );
		}
		else
		{
			exp = keyChooser.getText( ).trim( );
		}
		return exp;
	}
}