问题描述

使用填充有项目的常规 QComboBox，如果 currentIndex 设置为 -1，则小部件为空.在组合框中显示初始描述性文本(例如--选择国家/地区--"、--选择主题--"等)会非常有用，该文本未显示在下拉列表中.

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.

我在文档中找不到任何内容，也没有找到任何以前的问题的答案.

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

推荐答案

Combo Box API 中似乎没有预料到这种情况.但是由于底层模型的灵活性，您似乎应该能够将您的 --Select Country-- 添加为第一个合法"项目，然后使其不被用户选择:

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);

根据您想要的精确行为，您可能希望改用 setEnabled.或者我个人更喜欢它，如果它只是我可以将其设置回的不同颜色的项目:

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，如何更改 QComboBox 的一项的文本颜色?(C++)

(我不喜欢当我点击某个东西然后被困在我无法回到原来的地方时，即使它是一个没有选择的状态！)

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