Cannot sort the first column that freezed.

[annpt1]

I'm not able to sort the first column if I set it to freeze. Is there any tip to archive that? Many thanks

I use ZMJClassData example.
With these 2 delegations implemented. However, I cannot receive the sort event if I click on top row of the first column.

- (NSInteger)frozenRows:(SpreadsheetView *)spreadsheetView {
    return 1;
}

- (NSInteger)frozenColumns:(SpreadsheetView *)spreadsheetView {
    return 1;
}