qt确实会自动生成"合成"鼠标事件，以允许仅为鼠标设计的应用程序在触摸屏上工作。
要区分来自物理鼠标和合成鼠标的事件，可以执行以下操作：
1.将图形项目的所有事件处理代码从mousePressEvent、mouseMoveEvent和mouseReleaseEvent移动到sceneEvent方法。您应该在case QEvent：：GraphicsSceneMousePress、QEvent：：GraphicsSceneMouseMove和QEvent：：GraphicsSceneMouseRelease的switch语句中添加case。
1.在上述sceneEvent情况下，检查您接收的事件是否来自物理鼠标，而不是合成的。通过将事件指针转换为QGraphicsSceneMouseEvent * 并仅处理source（）方法返回Qt：：MouseEventNotSynthesized的事件来执行此操作
示例：

bool MapGraphicItem::sceneEvent(QEvent * event)
{
    switch (event->type()) {
    case QEvent::GraphicsSceneMousePress:
        if (event && ((QGraphicsSceneMouseEvent*)event)->source() == Qt::MouseEventNotSynthesized)
            handleMousePress();
        return true;
    case QEvent::GraphicsSceneMouseMove:
        if (event && ((QGraphicsSceneMouseEvent*)event)->source() == Qt::MouseEventNotSynthesized)
            handleMouseMove();
        return true;
    case QEvent::GraphicsSceneMouseRelease:
        if (event && ((QGraphicsSceneMouseEvent*)event)->source() == Qt::MouseEventNotSynthesized)
            handleMouseRelease();
        return true;
    // i left the rest of your while block unchanged
    case QEvent::TouchBegin:
    case QEvent::TouchUpdate:
    case QEvent::TouchEnd:
        QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
        QList<QTouchEvent::TouchPoint> touchPoints = touchEvent->touchPoints();
        if (touchPoints.count() == 2) {
            //do the zoom
            }
        return true;
    }

    return QGraphicsItem::sceneEvent(event);
}