c++ - 谜团: In Qt, 为什么会调用editorEvent，但不会调用createEditor？

Question

我正在子类化 QAbstractItemDelegate。这是我的代码。欢迎提出建议:

QWidget *ParmDelegate::createWidget(Parm *p, const QModelIndex &index) const {
    QWidget *w;
    if (index.column() == 0) {
        w = new QLabel(p->getName().c_str());
    } else {
        if (p->isSection())
            return NULL;
        w = p->createControl();
    }
    return w;
}

QWidget *ParmDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const {
    cout << "createEditor called" << endl;
    Parm    *p = reinterpret_cast<Parm*>(index.internalPointer());
    QWidget *retval = createWidget(p, index);
    retval->setFocusPolicy(Qt::StrongFocus);
    retval->setParent(parent);
    return retval;
}

void ParmDelegate::updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const {
    QRect rect(option.rect);
    editor->setGeometry(QRect(QPoint(0,0), rect.size()));
}

void ParmDelegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {
    Parm    *p = reinterpret_cast<Parm*>(index.internalPointer());
    scoped_ptr<QWidget> w(createWidget(p, index));
    if (!w)
        return;
    QRect rect(option.rect);
    w->setGeometry(QRect(QPoint(0,0), rect.size()));
    w->render(painter, rect.topLeft());
}

QSize ParmDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const {
    Parm    *p = reinterpret_cast<Parm*>(index.internalPointer());
    scoped_ptr<QWidget> w(createWidget(p, index));
    if (!w)
        return QSize(0,0);
    return w->sizeHint();
}

bool ParmDelegate::editorEvent(QEvent * event, QAbstractItemModel * model, const QStyleOptionViewItem & option, const QModelIndex & index ) {
    cout << "editorEvent called" << endl;
    return false;
}

运行时，我只看到每次编辑事件都会调用 editorEvent 两次——没有 createEditor!

Answer 1

来自 Qt 的 AbstractItemDelegate 文档:

To provide custom editing, there are two approaches that can be used. The first approach is to create an editor widget and display it directly on top of the item. To do this you must reimplement createEditor() to provide an editor widget, setEditorData() to populate the editor with the data from the model, and setModelData() so that the delegate can update the model with data from the editor.

The second approach is to handle user events directly by reimplementing editorEvent().

这似乎表明您缺少触发第一种方法的内容。我的猜测是您的模型的 data() 函数没有为 Qt::EditRole 选项返回正确的值。