QT QCombBox 控件設置下拉選項中某項不可選

QComboBox *editor = new QComboBox(this);
comboBox->addItems(QStringList()<<tr("Always")<<tr("Never")<<tr("Motion detection")<<tr("Timer recording"));
QVariant v(0);
// 序號為2的選項（第三個）不可選
comboBox->setItemData(2, v, Qt::UserRole - 1);
// 選項背景置灰
comboBox->setItemData(2, Qt::lightGray, Qt::BackgroundColorRole);
return editor;