QT Drag and Drop a QLabel into a QGraphicsView, how to?

[jiapei100]

Hi, all:

Sorry to bug you once again.

I'm trying to drag and drop a QLabel into a QGraphicsView.

My inherited label class looks like:

class CQtShapesLabel : public QLabel
{
Q_OBJECT
 
 
public:
 
 
explicit CQtShapesLabel(QWidget *parent = 0, int type = 0) : QLabel(parent), m_iType(type)
{
// this->m_qMimeData = NULL;
// this->m_qDrag = NULL;
}
 
 
virtual ~CQtShapesLabel() {}
 
 
protected:
// void dragEnterEvent(QDragEnterEvent *event);
// void dragMoveEvent(QDragMoveEvent *event);
void mousePressEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);
 
 
private:
// QMimeData* m_qMimeData;
// QDrag * m_qDrag;
int m_iType;
};

class CQtShapesLabel : public QLabel
{
Q_OBJECT


public:


explicit CQtShapesLabel(QWidget *parent = 0, int type = 0) : QLabel(parent), m_iType(type)
{
// this->m_qMimeData = NULL;
// this->m_qDrag = NULL;
}


virtual ~CQtShapesLabel() {}


protected:
// void dragEnterEvent(QDragEnterEvent *event);
// void dragMoveEvent(QDragMoveEvent *event);
void mousePressEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);


private:
// QMimeData* m_qMimeData;
// QDrag * m_qDrag;
int m_iType;
};

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and mousePressEvent() function is defined as:

void CQtShapesLabel::mousePressEvent(QMouseEvent *event)
{
    QPixmap pixmap = *this->pixmap();
 
    QByteArray itemData;
    QDataStream dataStream(&itemData, QIODevice::WriteOnly);
    dataStream << pixmap << QPoint(event->pos());
 
    QMimeData* m_qMimeData = new QMimeData;
    m_qMimeData->setData("application/x-dnditemdata", itemData);
 
    QDrag* m_qDrag = new QDrag(this);
    m_qDrag->setMimeData(m_qMimeData);
    m_qDrag->setPixmap(pixmap);
    m_qDrag->setHotSpot(event->pos());
 
    QPixmap tempPixmap = pixmap;
    QPainter painter;
    painter.begin(&tempPixmap);
    painter.fillRect(pixmap.rect(), QColor(127, 127, 127, 127));
    painter.end();
 
    this->setPixmap(tempPixmap);
 
    if (m_qDrag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction) == Qt::MoveAction)
        this->close();
    else
    {
        this->show();
        this->setPixmap(pixmap);
    }
}

void CQtShapesLabel::mousePressEvent(QMouseEvent *event)
{
    QPixmap pixmap = *this->pixmap();

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

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

    QDrag* m_qDrag = new QDrag(this);
    m_qDrag->setMimeData(m_qMimeData);
    m_qDrag->setPixmap(pixmap);
    m_qDrag->setHotSpot(event->pos());

    QPixmap tempPixmap = pixmap;
    QPainter painter;
    painter.begin(&tempPixmap);
    painter.fillRect(pixmap.rect(), QColor(127, 127, 127, 127));
    painter.end();

    this->setPixmap(tempPixmap);

    if (m_qDrag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction) == Qt::MoveAction)
        this->close();
    else
    {
        this->show();
        this->setPixmap(pixmap);
    }
}

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My inherited QGraphicsView class looks like:

class QTVIEWS_EXPORT CImageView : public QGraphicsView
{
Q_OBJECT
 
 
 
 
protected:
//void paintEvent(QPaintEvent *event);
void dragEnterEvent(QDragEnterEvent *event);
void dragMoveEvent(QDragMoveEvent *event);
void dragLeaveEvent(QDragLeaveEvent *event);
void dropEvent(QDropEvent *event);
// void mousePressEvent(QMouseEvent *event);
 
 
 
 
public:
 
 
CImageView( QWidget *parent = 0, unsigned int idx = 0 );
virtual ~CImageView( );
 
 
};

class QTVIEWS_EXPORT CImageView : public QGraphicsView
{
Q_OBJECT




protected:
//void paintEvent(QPaintEvent *event);
void dragEnterEvent(QDragEnterEvent *event);
void dragMoveEvent(QDragMoveEvent *event);
void dragLeaveEvent(QDragLeaveEvent *event);
void dropEvent(QDropEvent *event);
// void mousePressEvent(QMouseEvent *event);




public:


CImageView( QWidget *parent = 0, unsigned int idx = 0 );
virtual ~CImageView( );


};

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When testing, I tried to print out something in all functions, but no matter how I tried, I found

CQtShapesLabel::mouseReleaseEvent(QMouseEvent*event); // understandable
CImageView::dragLeaveEvent(QDragLeaveEvent*event); // should be able to response when the drag leaves this view
CImageView::dropEvent(QDropEvent*event); // should be able to response when the drag tries to drop something
CImageView::dragMoveEvent(QDragMoveEvent*event) // should be able to response when the drag keeps moving inside the view

never responses. Why is it so? Can anybody help to explain please....


Best Regards
Pei