Drag and Drop

[cwnelatury]

Hey everyone

I want a picture label that is on top of another bigger picture label to be dragged and dropped.

so in essence...I want to move a label from one location to another.

There were some tutorials online but they were too advanced for me.

Could someone please show/simplify to me how to do this.

Thanks

[wysota]

What did you already try?

[cwnelatury]

I got the following drag and drop code from another program.
I think I have to mold this code with my program so it can drag picture labels.

I created my program using Qt designer...so i am a little lost how to change my ui_mainwindow.h so labels can be dragged.

Please help..
thanks

void DragWidget::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();
     }
 }
 
 void DragWidget::dragMoveEvent(QDragMoveEvent *event)
 {
     if (event->mimeData()->hasFormat("application/x-dnditemdata")) {
         if (event->source() == this) {
             event->setDropAction(Qt::MoveAction);
             event->accept();
         } else {
             event->acceptProposedAction();
         }
     } else {
         event->ignore();
     }
 }
 
 void DragWidget::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;
 
         QLabel *newIcon = new QLabel(this);
         newIcon->setPixmap(pixmap);
         newIcon->move(event->pos() - offset);
         newIcon->show();
         newIcon->setAttribute(Qt::WA_DeleteOnClose);
 
         if (event->source() == this) {
             event->setDropAction(Qt::MoveAction);
             event->accept();
         } else {
             event->acceptProposedAction();
         }
     } else {
         event->ignore();
     }
 }
 
 void DragWidget::mousePressEvent(QMouseEvent *event)
 {
     QLabel *child = static_cast<QLabel*>(childAt(event->pos()));
     if (!child)
         return;
 
     QPixmap pixmap = *child->pixmap();
 
     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());
 
     QPixmap tempPixmap = pixmap;
     QPainter painter;
     painter.begin(&tempPixmap);
     painter.fillRect(pixmap.rect(), QColor(127, 127, 127, 127));
     painter.end();
 
     child->setPixmap(tempPixmap);
 
     if (drag->exec(Qt::CopyAction | Qt::MoveAction, Qt::CopyAction) == Qt::MoveAction)
         child->close();
     else {
         child->show();
         child->setPixmap(pixmap);
     }
 }

void DragWidget::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();
     }
 }

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

 void DragWidget::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;

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

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

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

     QPixmap pixmap = *child->pixmap();

     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());

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

     child->setPixmap(tempPixmap);

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

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[wysota]

I got the following drag and drop code from another program.
I think I have to mold this code with my program so it can drag picture labels.

And what doesn't work?

so i am a little lost how to change my ui_mainwindow.h so labels can be dragged.

We don't change ui_*.h files. We provide host classes for them.