Drag & drop between two QtreeWidgets

[excalibur1491]

Hi,

I have been working in a quite big project where there was a Qwidget integrated in a QDeclarativeView for a few months, and I had a bug that I am trying to solve. To solve it I am reducing the problem a quite little example.

My problem is taht I have two QTreeWidgets and I would like to do drag and drop from one to an other (and vice-versa). I am able of drag and dropping QTreeWidgetItems, but, when I drop a QTreeWidgetItem that has children, I lose them and only the parent is dropped.

I solved this problem by reimplementing the dropEvent and rebuilding the whole tree structure each time, but I am lloking for a better solution because that wasn't efficient and I couldn't implement the Ctrl-Z functionnality for those drag and drops since I was destroying objects all the time... Well, this is what I have:

@
#include <QApplication>
#include <QDebug>
#include <QObject>
#include <QWidget>
#include <QString>
#include <QTextStream>
#include <QIODevice>
#include <QMainWindow>
#include <QVBoxLayout>

#include "KTreeWidget.h"
#include "KAbstractItem.h"
#include "KItem.h"
#include "KItemGroup.h"

int main(int argc, char* argv[]){

QApplication app(argc, argv);

QMainWindow window = new QMainWindow();
QWidget central = new QWidget(window);
QVBoxLayout *layout = new QVBoxLayout();

KTreeWidget* kv = new KTreeWidget(window);
KTreeWidget* trash = new KTreeWidget(window);

layout->addWidget(kv);
layout->addWidget(trash);

central->setLayout(layout);

KItem* kiarr[5];
for (int i = 0 ; i < 5 ; i++){
kiarr[i] = new KItem(kv);
kiarr[i]->setText(0,QString("Item %1").arg(i));
}
KItemGroup* kgarr[5];
for (int i = 0 ; i < 5 ; i++){
kgarr[i] = new KItemGroup(trash);
kgarr[i]->setText(0,QString("Group %1").arg(i));
}

window->setCentralWidget(central);
window->show();

return app.exec();
}
@

My QTreeWidget:
KtreeWidget.h
@
#ifndef KTW_H
#define KTW_H

#include <QTreeWidget>

class KTreeWidget: public QTreeWidget{
Q_OBJECT

private:
QTreeWidgetItem* _header;

public:
KTreeWidget(QWidget* w = NULL);
};

#endif
@
and KTreeWidget.cc:
@
#include "KTreeWidget.h"

KTreeWidget::KTreeWidget(QWidget* w):QTreeWidget(w){
setColumnCount(3);
_header = new QTreeWidgetItem(NULL);
_header->setText(0,"Title");
_header->setText(1,"Edit");
_header->setText(2,"Open");
this->setDefaultDropAction(Qt::MoveAction);
setHeaderItem(_header);
setDragEnabled(true);
setAcceptDrops(true);
}
@

And the items (3 classes, in order to distinguish groups and leafs):
@
#ifndef KABSI_H
#define KABSI_H

#include <QObject>
#include <QTreeWidgetItem>
#include <QTreeWidget>

class KAbstractItem : public QObject, public QTreeWidgetItem{
Q_OBJECT
public:
KAbstractItem(QTreeWidget* p = NULL);
};

#endif
@
@
#include "KAbstractItem.h"
KAbstractItem::KAbstractItem(QTreeWidget* p):QTreeWidgetItem(p){}
@
@
#ifndef KI_H
#define KI_H

#include "KAbstractItem.h"

class KItem : public KAbstractItem{
Q_OBJECT
public:
KItem(QTreeWidget* p);
};

#endif
@
@
#include "KItem.h"

KItem::KItem(QTreeWidget* p):KAbstractItem(p){
setFlags(Qt::ItemIsSelectable
| Qt::ItemIsEditable
| Qt::ItemIsDragEnabled
| Qt::ItemIsUserCheckable
| Qt::ItemIsEnabled);
}
@

@
#ifndef KIG_H
#define KIG_H

#include "KAbstractItem.h"

class KItemGroup : public KAbstractItem{
Q_OBJECT
public:
KItemGroup(QTreeWidget* p);
};

#endif
@
@
#include "KItemGroup.h"

KItemGroup::KItemGroup(QTreeWidget* p):KAbstractItem(p){
setFlags(Qt::ItemIsSelectable
| Qt::ItemIsEditable
| Qt::ItemIsDragEnabled
| Qt::ItemIsDropEnabled
| Qt::ItemIsUserCheckable
| Qt::ItemIsEnabled);
}
@

Whenever I do a drop of one of the Items in the first WTreeWifget inside one of the groups of the second one, it works, but it then I move a group to the top QTreeWidget, I lose all the children...

Could you tell me what I am doing wrong?
Thanks a lot!