Columns name replaced with numerals in QTableWidget

ajaxcrypto

I have a QTableWidget with fixed number of columns (5 to be precise). I specify the columns by QTableWidget::setColumnCount and then use QTableWidget::setHorizontalHeaderLabels to assign the header labels. But they are instead shown as numerals (1,2,3,4,5 instead of names).
So, I tried writing a loop, insert columns (QTableWidget::insertColumn(int)), create item and set name and set the header item for column (QTableWidget::setHorizontalHeaderItem(int, QTreeWidgetItem*)), I still get numerals. Any idea as to how should I display header labels?

Info: Windows 10, Qt 5.9, MSVC 15.

VRonin

Could you try:

for(int i=0;i<tableWidget->columnCount();++i)
tableWidget->model()->setHeaderData(i,Qt::Horizontal,QStringLiteral("Column %1").arg(i+1));

ajaxcrypto

I tried doing that, debugging the issue, it seems like the headers items are all NULL, i.e. in QTableModel::setHeaderData, the horizontalHeaderItems.size() is 5, but all of them are nullptr.

ajaxcrypto

I have tried doing the following thing:

for (auto col = 0; col < headers.size(); ++col) {
        auto hitem = new QTableWidgetItem;
        hitem->setText(headers[col]);
        table->setHorizontalHeaderItem(col, hitem);
        table->model()->setHeaderData(col, Qt::Horizontal, headers[col], Qt::DisplayRole);
}

When I loop and print by QTableWidgetItem::text, I get the correct labels, but it still displays 1, 2, 3, 4, 5 in GUI.

VRonin

Can't reproduce, this works for me:

#include <QApplication>
#include <QTableWidget>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QTableWidget wid;
    wid.setRowCount(10);
    wid.setColumnCount(5);
    for(int i=0;i<wid.columnCount();++i){
        wid.setHorizontalHeaderItem(i, new QTableWidgetItem);
        Q_ASSUME(wid.model()->setHeaderData(i,Qt::Horizontal,QStringLiteral("Column %1").arg(i+1)));
    }
    wid.show();
    return a.exec();
}

Are you setting the column count to 0 anywhere in your code?

ajaxcrypto

I just did a column count, I get 5, not 0. So, column count is ok. Even the rows I add are ok, the trouble is with the headers, no matter what I do, I am always seeing numerals only.

VRonin

Did you try my minimal example above?
do you, ever, in your code call table->setColumnCount(0) or remove columns?

ajaxcrypto

The minimal example works.
No, I dont. In the sample application, I have other tables, whose headers do show correctly. All tables are initialized by the same routine.

With VS debugger, I drilled down, it seems the data is indeed there, I can see the horizontal header names, but they dont get displayed.

ajaxcrypto

Ok, found the issue, but do not know what causes it. So the table is added to a stacked layout. When I actually navigate there, the QTableModel::horizontalHeaderItems has 5 NULL items. They are not there. The column count is still 5 however.

VRonin

Yeah, the behaviour of Qt models in that sense is quite inconsistent. If you used QStandardItemModel+QTableView, for example, you would not need to worry about this issue. It's always usefull to have methods that are assumed to work wrapped in Q_ASSUME as above. It would assert in debug mode if the setHeaderData failed

ajaxcrypto

I cannot (also don't wish to) switch to Model/View for this as I would merely be displaying a bunch of information in table, no interaction as such. Other QTableWidget are working fine in the application. I will try to track down the issue. Also, setHeaderData does not fail either.

CNCer

I know that I am too late but I had the same problem and managed to solve it. I am posting my solution to help other people in the future.
In my case, adding the QtableWidget to a stacked layout had nothing to do with the problem. In my code I used QTableWidget::clear() this clears the table including the header. To clear the content only and leave the header as is use QTableWidget:: clearContents ()