如果使用 Qt::DecorationRole，拖放时崩溃

Question

以下实现工作正常：

ListModel::ListModel(QObject *parent) : QAbstractListModel(parent) {}

QVariant ListModel::data(const QModelIndex &index, int role) const {
    QVariant result;
    if (index.row() > -1 && index.row() < items.size()) {
        if (role == Qt::DisplayRole || role == Qt::EditRole)
            result = items.at(index.row());
//      else if (role == Qt::DecorationRole)
//          result = qApp->style()->standardIcon(QStyle::SP_DirIcon);
    }
    return result;}

Qt::ItemFlags ListModel::flags(const QModelIndex &index) const {
    Qt::ItemFlags flags = Qt::ItemIsSelectable | Qt::ItemIsDragEnabled | Qt::ItemIsEnabled;
    if (!index.isValid()) flags = flags | Qt::ItemIsDropEnabled;
    return flags;}

bool ListModel::insertRows(int row, int count, const QModelIndex &parent) {
    if (count < 1 || row < 0 || row > rowCount(parent))
        return false;
    beginInsertRows(QModelIndex(), row, row + count - 1);
    for (int i = 0; i < count; ++i)
        items.insert(row, QString());
    endInsertRows();
    return true;}

bool ListModel::removeRows(int row, int count, const QModelIndex &parent) {
    if (count < 1 || row < 0 || (row + count) > rowCount(parent))
        return false;
    beginRemoveRows(QModelIndex(), row, row + count - 1);
    for (int i = 0; i < count; ++i)
        items.removeAt(row);
    endRemoveRows();
    return true;}

int ListModel::rowCount(const QModelIndex &parent) const {
    if (parent.isValid()) return 0;
    return items.count();}

bool ListModel::setData(const QModelIndex &index, const QVariant &value, int role) {
    const int indexRow = index.row();
    if (indexRow > -1 && indexRow < items.count()) {
        if (role == Qt::DisplayRole || role == Qt::EditRole) {
            items.replace(indexRow, value.toString());
            emit dataChanged(index, index, QVector<int>() << role);
            return true;}}
    return false;}

Qt::DropActions ListModel::supportedDropActions() const {
    return Qt::MoveAction;}

但是一旦 data() 中的这两行取消注释，项目的拖放操作就会开始使应用程序崩溃：

0 __GI_raise /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.23.so 54 0x7ffff6400418
1 __GI_abort /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.23.so 89 0x7ffff640201a
2 __gnu_cxx::__verbose_terminate_handler() 0x7ffff6a3984d
3 ?? 0x7ffff6a376b6 4 std::terminate() 0x7ffff6a37701
5 __cxa_throw 0x7ffff6a37919 6 qBadAlloc() 0x7ffff6dba0e2
7 QAbstractItemModel::decodeData(int, int, QModelIndex const&, QDataStream&) 0x7ffff6f5bb28
8 QAbstractListModel::dropMimeData(QMimeData const *, Qt::DropAction, int, int, QModelIndex const&) 0x7ffff6f5c8af
9 QAbstractItemView::dropEvent(QDropEvent *) 0x7ffff7affc6c

这里有一个可以玩的小程序：

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    QMainWindow *mainWindow = new QMainWindow;
    QListView *listView = new QListView;
    ListModel *listModel = new ListModel;
    listView->setSelectionMode(QAbstractItemView::ExtendedSelection);
    listView->setDragDropMode(QAbstractItemView::InternalMove);
    listModel->insertRows(0, 3);
    listModel->setData(listModel->index(0), "alpha", Qt::DisplayRole);
    listModel->setData(listModel->index(1), "beta", Qt::DisplayRole);
    listModel->setData(listModel->index(2), "gamma", Qt::DisplayRole);
    listView->setModel(listModel);
    mainWindow->setCentralWidget(listView);
    mainWindow->show();
    return app.exec();}

Kubuntu 16.04 64 位，Qt 5.5.1

Answer 1

在我从 Qt 安装程序安装 Qt 5.6.1 后，拖放停止导致程序崩溃。也许，来自 Ubuntu 个存储库的 Qt 包中存在错误。

如果使用 Qt::DecorationRole，拖放时崩溃

crash while drag-and-drop if Qt::DecorationRole is used

c++

qt

drag-and-drop

model-view