接受QGraphicsScene上的滴 [英] Accepting drops on a QGraphicsScene

问题描述

我正在尝试执行drag'n'drop一个 QGraphicsScene 。以下是我已经重载的事件：

  void TargetScene :: dragEnterEvent（QGraphicsSceneDragDropEvent * event）{
 bool acceptDrag = false; 
 const QMimeData * mime = event-> mimeData（）; 
 
 //是否存在图像？ 
 if（mime-> hasImage（））{
 QImage img = qvariant_cast< QImage>（mime-> imageData（））; 
 dragPix = QPixmap :: fromImage（img）; 
 acceptDrag =！dragPix.isNull（）; 
} 
 
 event-> setAccepted（acceptDrag）; 
} 
 
 void TargetScene :: dropEvent（QGraphicsSceneDragDropEvent * event）{
 //将拖动的像素图添加到场景
 QGraphicsPixmapItem * newPix = this-> addPixmap（dragPix ）; 
 newPix-> setPos（event-> pos（）。x（），event-> pos（）。y（））; 
} 
  

场景依然不会接受滴。我猜这是因为我不能在我的 QGraphicsScene 上 setAcceptDrops（true）

如何在图形场景中接受滴滴？

解决方案

这里的诀窍是还要接受QGraphicsScene :: dragMoveEvent（）！中的事件！

原因是DEFAULT实现，如果鼠标下没有任何项目则忽略拖放事件！ / p>

另请参阅： http://www.qtcentre.org/threads/8022-QGraphicsScene-doesn-t-accept-Drops

干杯

I'm trying to implement drag'n'drop for a QGraphicsScene. Here are the events I've overloaded:

void TargetScene::dragEnterEvent(QGraphicsSceneDragDropEvent *event) {
    bool acceptDrag = false;
    const QMimeData* mime = event->mimeData();

    // Is an image present?
    if (mime->hasImage()) {
        QImage img = qvariant_cast<QImage>(mime->imageData());
        dragPix = QPixmap::fromImage(img);
        acceptDrag = !dragPix.isNull();
    }

    event->setAccepted(acceptDrag);
}

void TargetScene::dropEvent(QGraphicsSceneDragDropEvent *event) {
    // Add dragged pixmap to scene
    QGraphicsPixmapItem* newPix = this->addPixmap(dragPix);
    newPix->setPos(event->pos().x(), event->pos().y());
}

The scene still won't accept drops. I'm guessing that's because I can't do setAcceptDrops(true) on my QGraphicsScene.

How do I accept drops on a graphics scene?

解决方案

The trick here is to ALSO accept the event in the QGraphicsScene::dragMoveEvent()!

The reason is the DEFAULT implementation which ignores drag and drop events if there is no item under the mouse!

Also refer to: http://www.qtcentre.org/threads/8022-QGraphicsScene-doesn-t-accept-Drops

Cheers

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