Qt官方示例-可拖拽本文

可对文本进行拖动到指定位置。

部分主要代码

• 当被鼠标拖动的对象进入其容器范围内时触发此事件

void DragWidget::dragEnterEvent(QDragEnterEvent *event)
{
    if (event->mimeData()->hasText()) {
        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept(); /* 接受拖拽事件 */
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
}

在一个拖动过程中，释放鼠标键时触发此事件

void DragWidget::dropEvent(QDropEvent *event)
{
    if (event->mimeData()->hasText()) {
        const QMimeData *mime = event->mimeData();
        QStringList pieces = mime->text().split(QRegularExpression(QStringLiteral("\\s+")),
                             QString::SkipEmptyParts);
        QPoint position = event->pos();
        QPoint hotSpot;

        QByteArrayList hotSpotPos = mime->data(hotSpotMimeDataKey()).split(' ');
        if (hotSpotPos.size() == 2) {
            /* 松开拖拽设置为当前位置 */
            hotSpot.setX(hotSpotPos.first().toInt()); 
            hotSpot.setY(hotSpotPos.last().toInt());
        }

        for (const QString &piece : pieces) {
            QLabel *newLabel = createDragLabel(piece, this);
            newLabel->move(position - hotSpot);
            newLabel->show();
            newLabel->setAttribute(Qt::WA_DeleteOnClose);

            position += QPoint(newLabel->width(), 0);
        }

        if (event->source() == this) {
            event->setDropAction(Qt::MoveAction);
            event->accept(); /* 接受拖拽事件 */
        } else {
            event->acceptProposedAction();
        }
    } else {
        event->ignore();
    }
    for (QWidget *widget : findChildren<QWidget *>()) {
        if (!widget->isVisible())
            widget->deleteLater();
    }
}

• 捕获鼠标按下事件

void DragWidget::mousePressEvent(QMouseEvent *event)
{
    QLabel *child = qobject_cast<QLabel*>(childAt(event->pos()));
    if (!child)
        return;

    QPoint hotSpot = event->pos() - child->pos();

    QMimeData *mimeData = new QMimeData;
    mimeData->setText(child->text());
    mimeData->setData(hotSpotMimeDataKey(),
                      QByteArray::number(hotSpot.x()) + ' ' + QByteArray::number(hotSpot.y()));

    qreal dpr = window()->windowHandle()->devicePixelRatio();
    QPixmap pixmap(child->size() * dpr);
    pixmap.setDevicePixelRatio(dpr);
    child->render(&pixmap);

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

    Qt::DropAction dropAction = drag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction);

    if (dropAction == Qt::MoveAction)
        child->close();
}

关于更多

• 在QtCreator软件可以找到：

• 或在以下Qt安装目录找到

C:\Qt\{你的Qt版本}\Examples\{你的Qt版本}\widgets\draganddrop\draggabletext

• 相关链接

https://doc.qt.io/qt-5/qtwidgets-draganddrop-draggabletext-example.html

• Qt君公众号后台回复『Qt示例』获取更多内容。