I wonder how can I achieve the effect when user single click on a column header of a grid panel. By default, the data will be sort by this column and the column header will display a small triangle on the right pointing up/down, depending on the sort order (ASC/DESC)

I call:
and the grid is sorted by the "sequenceNumber" column, but no triangle displayed, indicating the sort order

I call:
var sortOptions = new Array();
sortOptions['field'] = "sequenceNumber";
sortOptions['direction'] = "ASC";
myGridPanel.fireEvent("sortChange",myGridPanel, sortOptions);
Nothing happened

There is a "headerOnClick" event in the gridView.js that seems to do what I want, but it's a private function and I can not call it.

Anyone has advices? Thanks