Drag and Drop problems

[junix]

Hi people,

I'm using qt-creator to make a simple application with drag and drop system. The idea is understand the process.

I create a simple windows with two panels:
http://img6.imagebanana.com/img/c56hr2b9/thumb/Selection_002.png (http://www.imagebanana.com/view/c56hr2b9/Selection_002.png)

The idea is using drag and drop to change the icons from the panels.

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

QT_BEGIN_NAMESPACE
class QDragEnterEvent;
class QDropEvent;
QT_END_NAMESPACE

class MainWindow : public QMainWindow {
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();

protected:
void dragEnterEvent(QDragEnterEvent *event);
void dragMoveEvent(QDragMoveEvent *event);
void dropEvent(QDropEvent *event);
void mousePressEvent(QMouseEvent *event);

private:
Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::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 MainWindow::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 MainWindow::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 MainWindow::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);
}
}


To me is ok, but I've got some errors:


../drag/mainwindow.cpp:: In member function ‘virtual void MainWindow::dragEnterEvent(QDragEnterEvent*)â€⠄¢:
../drag/mainwindow.cpp:18: error: invalid use of incomplete type ‘struct QDragEnterEvent’
..drag-build-desktop/../../qtsdk-2010.05/qt/include/QtGui/qwidget.h:88: error: forward declaration of ‘struct QDragEnterEvent’
[...]

Thanks for all help.

Junix

[cincirin]

Just missing #include <QDragEnterEvent>

[junix]

Great!

Now is working.

Thank you cincirin.