Qt 拖放QFrame

我一直在看拖放示例，但仍然对它们感到困惑。特别是，我不知道在mousePressEvent（）和dropEvent（）中要做什么

我正在遵循并修改拖拽QLabel的示例。 以下是我认为QFrame的MousePresseEvent（）应该是什么样子。我试过了，我可以看到画框在移动，但是当我掉下来的时候我就失去了它

void SummaryBar::mousePressEvent(QMouseEvent *event)
{
    QFrame *child = static_cast<QFrame*>(childAt(event->pos()));
    if (!child)
        return;

    QPixmap pixmap = QPixmap::grabWidget(child);

    QByteArray itemData;
    QDataStream dataStream(&itemData, QIODevice::WriteOnly);
    dataStream << pixmap << QPoint(event->pos() - child->pos());

    QMimeData *mimeData = new QMimeData;
    mimeData->setData("application/x-dnditemdata", itemData);

    QDrag *drag = new QDrag(this);
    drag->setMimeData(mimeData);
    drag->setPixmap(pixmap);
    drag->setHotSpot(event->pos() - child->pos());


    if (drag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction) == Qt::MoveAction) {
        child->close();
    } else {
        child->show();

    }
}

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您是否覆盖以接受建议的拖放操作？我刚刚将该代码添加到原始帖子中。当我尝试拖动QFrame时，它并不总是起作用。在我真正拖动它之前，需要几次尝试。一旦我放下它，它就消失了。如果“event->source（）==this”，你就不会调用

acceptProposeAction

。我从Qt示例（DragableIcons）中获取了这段代码。这部分代码中没有AcceptProposeAction。我试着加上它，结果没有什么不同。

    void SummaryBar::dropEvent(QDropEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
        QByteArray itemData = event->mimeData()->data("application/x-dnditemdata");
        QDataStream dataStream(&itemData, QIODevice::ReadOnly);

        QPixmap pixmap;
        QPoint offset;
        dataStream >> pixmap >> offset;

        QFrame *newFrame = new QFrame(this);
        //newFrame->setPixmap(pixmap);
        newFrame->move(event->pos() - offset);
        newFrame->show();
        newFrame->setAttribute(Qt::WA_DeleteOnClose);

        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);  
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

void SummaryBar::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept();
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}    

I would greatly appreciate any help!!