Question1
If the event is received by the diagramWindow, and want it receive by the scene
which is currently displayed by a view
, then what you should do is pass the event to the view, that will convert it to a QGraphicsSceneDragDropEvent
and redirect it to the scene:
void DiagramWindow::dragMoveEvent(event)
{
view->dragMoveEvent(event);
}
Question 2
Don't know much about Drag event so can't help, but to get the previous behaviour depending on a if statement, you should do:
void MyDerivedClass::myEvent(event)
{
if(...)
// do specific behaviour
else
QBaseClass::myEvent(event); // default behaviour
}
assuming your class MyDerivedClass
(in your case, DiagramWindow
) inherits from the Qt class QBaseClass
(in your case, QMainWindow
?), and the event method you want to override is myEvent()
(in your case, dragMoveEvent
).
Working example:
I don't know exacly what your class DiagramWindow is, but here is a working example that should give you all the necessary ideas to make it work in your case. I suggest you start from this working example, and modify it to get what you need.
main.cpp:
#include <QApplication>
#include "Scene.h"
#include "View.h"
int main(int argc, char * argv[])
{
QApplication app(argc,argv);
Scene * scene1 = new Scene(1);
View * view1 = new View(scene1, 1);
Scene * scene2 = new Scene(2);
View * view2 = new View(scene2,2);
view1->show();
view2->show();
return app.exec();
}
Scene.h:
#ifndef SCENE_H
#define SCENE_H
#include <QGraphicsScene>
#include <QGraphicsEllipseItem>
class Item;
class Item: public QGraphicsEllipseItem
{
public:
Item(int x,int y);
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
};
class Scene: public QGraphicsScene
{
public:
Scene(int i);
protected:
virtual void dragEnterEvent ( QGraphicsSceneDragDropEvent * event );
virtual void dragLeaveEvent ( QGraphicsSceneDragDropEvent * event );
virtual void dragMoveEvent ( QGraphicsSceneDragDropEvent * event );
virtual void dropEvent ( QGraphicsSceneDragDropEvent * event );
int i;
};
#endif
Scene.cpp:
#include "Scene.h"
#include <QtDebug>
#include <QGraphicsSceneMouseEvent>
#include <QDrag>
#include <QMimeData>
Item::Item(int x, int y) : QGraphicsEllipseItem(x,y,50,50) {}
void Item::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
qDebug() << "item mouse press";
// Create the mime data that will be transfered from one scene
// to another
QMimeData * mimeData = new QMimeData;
// In our case, the data will be the address of the item.
//
// Note: This is UNSAFE, and just for the sake of example. The
// good way to do it is to create your own mime type, containing
// all the information necessary to recreate an identical Item.
//
// This is because drag and drop is meant to work between
// applications, and the address of your item is not accessible
// by other applications (deferencing it would produce a
// segfault). It works fine in this case since you perform a
// drag and drop between different windows of the same
// application.
Item * item = this;
QByteArray byteArray(reinterpret_cast<char*>(&item),sizeof(Item*));
mimeData->setData("Item",byteArray);
// start the event
QDrag * drag = new QDrag(event->widget());
drag->setMimeData(mimeData);
drag->start();
}
Scene::Scene(int i) : i(i)
{
Item * item = new Item(100+100*i,100);
addItem(item);
}
void Scene::dragEnterEvent ( QGraphicsSceneDragDropEvent * event )
{
qDebug() << "scene" << i << "drag enter";
}
void Scene::dragLeaveEvent ( QGraphicsSceneDragDropEvent * event )
{
qDebug() << "scene" << i << "drag leave";
}
void Scene::dragMoveEvent ( QGraphicsSceneDragDropEvent * event )
{
qDebug() << "scene" << i << "drag move";
}
void Scene::dropEvent ( QGraphicsSceneDragDropEvent * event )
{
qDebug() << "scene" << i << "drop";
// retrieve the address of the item from the mime data
QByteArray byteArray = event->mimeData()->data("Item");
Item * item = *reinterpret_cast<Item**>(byteArray.data());
// add the item to the scene (automatically remove it from the
// other scene)
addItem(item);
}
View.h:
#ifndef VIEW_H
#define VIEW_H
#include <QGraphicsView>
#include "Scene.h"
class View: public QGraphicsView
{
public:
View(Scene * scene, int i);
protected:
virtual void dragEnterEvent ( QDragEnterEvent * event );
virtual void dragLeaveEvent ( QDragLeaveEvent * event );
virtual void dragMoveEvent ( QDragMoveEvent * event );
virtual void dropEvent ( QDropEvent * event );
private:
Scene * scene_;
int i;
};
#endif
View.cpp:
#include "View.h"
#include <QtDebug>
View::View(Scene * scene, int i) :
QGraphicsView(scene),
scene_(scene),
i(i)
{
}
void View::dragEnterEvent ( QDragEnterEvent * event )
{
qDebug() << "view" << i << "drag enter";
QGraphicsView::dragEnterEvent(event);
}
void View::dragLeaveEvent ( QDragLeaveEvent * event )
{
qDebug() << "view" << i <<"drag leave";
QGraphicsView::dragLeaveEvent(event);
}
void View::dragMoveEvent ( QDragMoveEvent * event )
{
qDebug() << "view" << i << "drag move";
QGraphicsView::dragMoveEvent(event);
}
void View::dropEvent ( QDropEvent * event )
{
qDebug() << "view" << i << "drop";
QGraphicsView::dropEvent(event);
}
In your case, if you need to explicitly call view->someDragDropEvent(event)
from your DiagramWindow
, then you just have to change the protected:
to public:
. But I don't think it is necessary, just try without reimplementing the drag and drop event in DiagramWindow
, and it should automatically call the one of your view.