Qt 5.11 | Qt Widgets | Draggable Icons Example | dragwidget.cpp Example File

Qt 5.11.3 Reference Documentation

# dragwidget.cpp Example File

draganddrop/draggableicons/dragwidget.cpp

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      #include <QtWidgets>

      #include "dragwidget.h"

      DragWidget::DragWidget(QWidget *parent)
          : QFrame(parent)
      {
          setMinimumSize(200, 200);
          setFrameStyle(QFrame::Sunken | QFrame::StyledPanel);
          setAcceptDrops(true);

          QLabel *boatIcon = new QLabel(this);
          boatIcon->setPixmap(QPixmap(":/images/boat.png"));
          boatIcon->move(10, 10);
          boatIcon->show();
          boatIcon->setAttribute(Qt::WA_DeleteOnClose);

          QLabel *carIcon = new QLabel(this);
          carIcon->setPixmap(QPixmap(":/images/car.png"));
          carIcon->move(100, 10);
          carIcon->show();
          carIcon->setAttribute(Qt::WA_DeleteOnClose);

          QLabel *houseIcon = new QLabel(this);
          houseIcon->setPixmap(QPixmap(":/images/house.png"));
          houseIcon->move(10, 80);
          houseIcon->show();
          houseIcon->setAttribute(Qt::WA_DeleteOnClose);
      }

      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);
          }
      }