How to set non-selectable default text on QComboBox?

问题

Using a regular QComboBox populated with items, if currentIndex is set to -1, the widget is empty. It would be very useful to instead have an initial descriptive text visible in the combo box(e.g. "--Select Country--", "--Choose Topic--", etc.) which is not shown in the dropdown list.

I couldn't find anything in the documentation, nor any previous questions with answers.

回答1:

It doesn't appear that case was anticipated in the Combo Box API. But with the underlying model flexibility it seems you should be able to add your --Select Country-- as a first "legitimate" item, and then keep it from being user selectable:

QStandardItemModel* model =
        qobject_cast<QStandardItemModel*>(comboBox->model());
QModelIndex firstIndex = model->index(0, comboBox->modelColumn(),
        comboBox->rootModelIndex());
QStandardItem* firstItem = model->itemFromIndex(firstIndex);
firstItem->setSelectable(false);

Depending on what precise behavior you want, you might want to use setEnabled instead. Or I'd personally prefer it if it was just a different color item that I could set it back to:

Qt, How do I change the text color of one item of a QComboBox? (C++)

(I don't like it when I click on something and then get trapped to where I can't get back where I was, even if it's a nothing-selected-yet-state!)

来源：https://stackoverflow.com/questions/7632645/how-to-set-non-selectable-default-text-on-qcombobox