c++ - Qt QAbstractItemModel-项目删除崩溃

我正在使用具有层次结构的Qt类编写应用程序，并且需要在树形 View 中显示它(我正在使用QTreeView小部件)。数据本身如下所示:

class StatisticsEntry
{
 // additional data management methods
 ...

bool setData(int column, const QVariant &value)
{
    if (column < 0 || column >= _data.size())
        return false;

    _data[column] = value;
    return true;
}

private:
    // each item has a parent item except the top-most one
    StatisticsEntry *_parent;
    // each item may have child items which are accessible through the following member
    QList<StatisticsEntry*> _children;
    // each item is defined by a set of vallues stored in the following vector
    QVector<QVariant> _data;
}

我有一个称为QStatisticsModel的类，它实现QAbstractItemModel-使用它来处理和呈现存储在StatisticsEntry树中的数据。
该类具有一个称为addStatisticsData的方法，该方法用于将StatisticsEntry记录推入模型。该方法大致如下所示:

QModelIndex StatisticsModel::addStatisticsData(const QString &title, const QString &description, const QModelIndex &parent)
{
    int row = rowCount(parent);
    if (!insertRow(row, parent))
        return QModelIndex();

    // Get new item index
    QModelIndex child = index(row, 0, parent);

    // set item data
    setTitle(child, title);
    setDescription(child, description);

    return child;
}

SetTitle和setDescription方法相同-这是setTitle一种:

void StatisticsModel::setTitle(const QModelIndex &index, const QString& title)
{
    QModelIndex columnIndex = this->index(index.row(), StatColumn::Title, index.parent());
    this->setData(columnIndex, title, Qt::EditRole);
}

setData方法如下:

bool StatisticsModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (role != Qt::EditRole)
        return false;

    int column = index.column();

    StatisticsEntry *item = getItem(index);
    if (!item->setData(column, value))
        return false;

    emit dataChanged(index, index);

    return true;
}

剩下的就是getItem方法:

StatisticsEntry *StatisticsModel::getItem(const QModelIndex &index) const
{
    if (index.isValid())
    {
        StatisticsEntry *item = static_cast<StatisticsEntry*>(index.internalPointer());
        if (item)
            return item;
    }

    return _rootItem;
}

谈到添加新条目和修改现有条目，这就是全部。在我的应用程序中，我还实现了QSortFilterProxyModel-没什么特别的，只是lessThan方法。我使用代理模型在QTreeView中提供了显示数据的排序功能。以下代码将模型连接到Treeview小部件:

在主窗口的标题中:

...
StatisticsModel* _statisticsModel;
StatisticsProxyModel* _statisticsProxyModel;
...

在主要寡妇的构造函数中

...
_statisticsModel = new StatisticsModel(ths);
_statisticsProxyModel = new StatisticsProxyModel(htis);
...
_statisticsProxyModel->setSourceModel(_statisticsModel);
ui->statisticsTreeView->setModel(_statisticsProxyModel);
...

该应用程序还具有一个按钮，允许我从模型中删除选定的项目-我目前仅使用QTreeView::selectionModel()-> currentIndex进行测试，目前暂无多重选择。

我为StatisticsModel::removeRows方法使用以下代码

bool StatisticsModel::removeRows(int position, int rows, const QModelIndex &parent)
{
    StatisticsEntry *parentItem = getItem(parent);

    bool success1 = true;
    bool success2 = true;
    beginRemoveRows(parent, position, position + rows - 1);
    for (int i = position + rows - 1; i >= position; i--)
    {
        QModelIndex child = index(i, 0, parent);
        QString title = this->title(child); // the title method is the getter method that matches the setTitle one
        success1 = success1 && removeRows(0, rowCount(child), child); //rowCount is implemented to return the number of items stored in StatisticsEntry::_children list for the specified parent index
        success2 = success2 && parentItem->removeChild(i); // deletes an entry from the StatisticsEntry::_children list
    }
    endRemoveRows();
    return success1 && success2;
}

问题是，有时当我使用QAbstractItemModel::removeRow方法删除项目时，会出现异常，并且堆栈跟踪如下所示:

StatisticsModel::parent StatisticsModel.cpp 307 0x13e7bf8
QModelIndex::parent qabstractitemmodel.h    393 0x72e57265
QSortFilterProxyModelPrivate::source_to_proxy   qsortfilterproxymodel.cpp   386 0x711963e2
QSortFilterProxyModel::mapFromSource    qsortfilterproxymodel.cpp   2514    0x7119d28b
QSortFilterProxyModel::parent   qsortfilterproxymodel.cpp   1660    0x7119a32c
QModelIndex::parent qabstractitemmodel.h    393 0x72e57265
QPersistentModelIndex::parent   qabstractitemmodel.cpp  347 0x72e58b86
QItemSelectionRange::isValid    qitemselectionmodel.h   132 0x70e3f62b
QItemSelection::merge   qitemselectionmodel.cpp 466 0x711503d1
QItemSelectionModelPrivate::finalize    qitemselectionmodel_p.h 92  0x7115809a
QItemSelectionModelPrivate::_q_rowsAboutToBeRemoved qitemselectionmodel.cpp 623 0x71151132
QItemSelectionModel::qt_static_metacall moc_qitemselectionmodel.cpp 113 0x711561c2
QMetaObject::activate   qobject.cpp 3547    0x72e8d9a4
QAbstractItemModel::rowsAboutToBeRemoved    moc_qabstractitemmodel.cpp  204 0x72f08a76
QAbstractItemModel::beginRemoveRows qabstractitemmodel.cpp  2471    0x72e5c53f
QSortFilterProxyModelPrivate::remove_proxy_interval qsortfilterproxymodel.cpp   558 0x71196ce7
QSortFilterProxyModelPrivate::remove_source_items   qsortfilterproxymodel.cpp   540 0x71196c7f
QSortFilterProxyModelPrivate::source_items_about_to_be_removed  qsortfilterproxymodel.cpp   841 0x71197c77
QSortFilterProxyModelPrivate::_q_sourceRowsAboutToBeRemoved qsortfilterproxymodel.cpp   1291    0x711995cc
QSortFilterProxyModel::qt_static_metacall   moc_qsortfilterproxymodel.cpp   115 0x7119d506
QMetaCallEvent::placeMetaCall   qobject.cpp 525 0x72e883fd
QObject::event  qobject.cpp 1195    0x72e894ba
QApplicationPrivate::notify_helper  qapplication.cpp    4550    0x709d710e
QApplication::notify    qapplication.cpp    3932    0x709d4d87
QCoreApplication::notifyInternal    qcoreapplication.cpp    876 0x72e6b091

奇怪的是，似乎所有与该项删除有关的直接方法调用都已经结束之后，这种情况才会发生。似乎代理模型正在寻找不应再出现的模型索引(或我认为)。 StatisticsModel::parent方法如下:

QModelIndex StatisticsModel::parent(const QModelIndex &index) const
{
    if (!index.isValid())
        return QModelIndex();

    StatisticsEntry *childItem = getItem(index);
    StatisticsEntry *parentItem = childItem->parent();

    if (NULL != parentItem)
        return createIndex(parentItem->childNumber(), 0, parentItem);
    return QModelIndex();
}

发生异常时，与上述方法中的childItem和parentItem变量相关联的值似乎无效-指针本身指向不可访问的内存，或者成员QLists没有条目或它们的条目违反了内存访问权限。
可能是父方法不正确，但是如何获取父索引-qabstractItemModel文档不鼓励在该方法中使用QModelIndex::parent，因为它将创建无限递归。

任何帮助，将不胜感激，

最佳答案

在执行StatisticsModel::removeRows时，您正在嵌套begingRemoveRows/endRemoveRows，AFAIK无法使用。你应该做:

bool StatisticsModel::removeRows(int position, int rows, const QModelIndex &parent)
{
    StatisticsEntry *parentItem = getItem(parent);

    bool success1 = true;
    bool success2 = true;
    for (int i = position + rows - 1; i >= position; i--)
    {
        QModelIndex child = index(i, 0, parent);
        QString title = this->title(child); // the title method is the getter method that matches the setTitle one
        success1 = success1 && removeRows(0, rowCount(child), child); //rowCount is implemented to return the number of items stored in StatisticsEntry::_children list for the specified parent index
        beginRemoveRows(parent, i, i);
        success2 = success2 && parentItem->removeChild(i); // deletes an entry from the StatisticsEntry::_children list
        endRemoveRows();
    }
    return success1 && success2;
}

关于c++ - Qt QAbstractItemModel-项目删除崩溃，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/9779775/