問題描述

使用填充有項目的常規(guī) QComboBox，如果 currentIndex 設(shè)置為 -1，則小部件為空.在組合框中顯示初始描述性文本(例如--選擇國家/地區(qū)--"、--選擇主題--"等)會非常有用，該文本未顯示在下拉列表中.

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.

我在文檔中找不到任何內(nèi)容，也沒有找到任何以前的問題的答案.

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

推薦答案

Combo Box API 中似乎沒有預(yù)料到這種情況.但是由于底層模型的靈活性，您似乎應(yīng)該能夠?qū)⒛?--Select Country-- 添加為第一個合法"項目，然后使其不被用戶選擇:

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);

根據(jù)您想要的精確行為，您可能希望改用 setEnabled.或者我個人更喜歡它，如果它只是我可以將其設(shè)置回的不同顏色的項目:

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 的一項的文本顏色?(C++)

(我不喜歡當(dāng)我點擊某個東西然后被困在我無法回到原來的地方時，即使它是一個沒有選擇的狀態(tài)！)

這篇關(guān)于如何在 QComboBox 上設(shè)置不可選擇的默認(rèn)文本?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！