How can I do drag and drop in a widget?

Drag and drop support in Qt is centered around the QDrag [qt.nokia.com] class that handles most of the details of a drag and drop operation.

In addition to creating a QDrag object, you need to reimplement dragMoveEvent() [qt.nokia.com] to accept the event and dropEvent() [qt.nokia.com] to handle the data dropped on the widget. Finally dragEnterEvent() [doc.qt.nokia.com] needs to be reimplemented to accept the event.

You also need to call

setAcceptDrops(true)

on the widgets that should be able to accept a drop.

For more information, read the general documentation [qt.nokia.com] on drag and drop:

The example below illustrates how this can be done.

#include <QtGui>
class MyDialog : public QWidget
{
Q_OBJECT
public:
MyDialog(QWidget *parent = 0);
public slots:
void makeDrag();
protected:
void dropEvent(QDropEvent *de);
void dragMoveEvent(QDragMoveEvent *de);
void dragEnterEvent(QDragEnterEvent *event);
};
class MyGroupBox : public QGroupBox
{
public:
MyGroupBox(QWidget *parent = 0) : QGroupBox("GroupBox", parent) {};
protected:
void dropEvent(QDropEvent *de);
void dragMoveEvent(QDragMoveEvent *de);
void dragEnterEvent(QDragEnterEvent *event);
};
MyDialog::MyDialog(QWidget *parent) : QWidget(parent)
{
QHBoxLayout *layout = new QHBoxLayout(this);
QPushButton *pushButton = new QPushButton("Click Me", this);
layout->addWidget(pushButton);
connect(pushButton, SIGNAL(pressed()), this, SLOT(makeDrag()));
MyGroupBox *box = new MyGroupBox(this);
layout->addWidget(box);
// Allow media to be dropped on the widget
setAcceptDrops(true);
box->setAcceptDrops(true);
}
void MyDialog::makeDrag()
{
QDrag *dr = new QDrag(this);
// The data to be transferred by the drag and drop operation is contained in a QMimeData object
QMimeData *data = new QMimeData;
data->setText("This is a test");
// Assign ownership of the QMimeData object to the QDrag object.
dr->setMimeData(data);
// Start the drag and drop operation
dr->start();
}
void MyDialog::dragMoveEvent(QDragMoveEvent *de)
{
// The event needs to be accepted here
de->accept();
}
void MyDialog::dragEnterEvent(QDragEnterEvent *event)
{
// Set the drop action to be the proposed action.
event->acceptProposedAction();
}
void MyDialog::dropEvent(QDropEvent *de)
{
// Unpack dropped data and handle it the way you want
qDebug("Contents: %s", de->mimeData()->text().toLatin1().data());
}
void MyGroupBox::dropEvent(QDropEvent *de)
{
// Unpack dropped data and handle it the way you want
qDebug("Contents: %s", de->mimeData()->text().toLatin1().data());
}
void MyGroupBox::dragMoveEvent(QDragMoveEvent *de)
{
// The event needs to be accepted here
de->accept();
}
void MyGroupBox::dragEnterEvent(QDragEnterEvent *event)
{
// Set the drop action to be the proposed action.
event->acceptProposedAction();
}
#include "main.moc"
int main(int argc, char **argv)
{
QApplication a(argc, argv);
MyDialog d;
d.show();
return a.exec();
}

How can I do drag and drop in a widget?

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How can I do drag and drop in a widget?

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