Drag and Drop between 3 QListViews

[digga]

Hi all,

I try to realize a drag and drop system between 3 QListViews, I thought about subclassing QAbstractListModel, each model inherits a QList<int>. I already searched around for solutions, but I didnt found any good example or explanation. What I already know is that I have to reimplement the functions in QAbstractListModel:

• rowCount()
• data()
• setData()
• headerData()

About the following I am not sure

• mimeTypes()
• mimeData()
• dropMimeData()
• supportedDropActions()

I think I also need a subclass of QListView and implement the following or don't I need to subclass ?

• setAcceptDrops(true);
• setDragEnabled(true);
• setDragDropMode(QAbstractItemView::InternalMove);
• setDropIndicatorShown(true);
• setSelectionMode(QAbstractItemView::SingleSelection);
• setDragDropMode(QAbstractItemView::DragDrop);

My problem is I didnt found any implementation examples of any mime or drop method. Also the user shouldn't be able to drop a item outside of a QListView, if he does so it should drop back from where it came.
Has anybody a good implementation for these methods?

[marsupial]

I think this is a very good introduction into the topic: http://doc.qt.nokia.com/4.7-snapshot/model-view-programming.html#using-drag-and-drop-with-item-views

Other than that, have a look at those examples on how to implement Drag and Drop:
http://doc-snapshot.qt-project.org/4.8/examples-draganddrop.html

How to subclass the actual model is being demontrated in multiple examples here: http://doc-snapshot.qt-project.org/4.8/examples-itemviews.html

And last but not least, the documentation talks a little about mime-data in models: http://qt-project.org/doc/qt-4.8/qabstractitemmodel.html#mimeData

[digga]

Ok, I read the articles you linked and implement the methods sofar. -But if I try to drag an item from one to another View it shows a crossed circle.-
Edit: Ok i can drag things around, but I am not possible to drop them:(
@ QList<int> list;
list << 2;
list << 4;
list << 5;

MODEL *model = new MODEL();
model->setPlayers(list);
ui->NotPossibleList->setModel(model);
ui->NotPossibleList->setAcceptDrops(true);
ui->NotPossibleList->setDragDropMode(QAbstractItemView::InternalMove);
ui->NotPossibleList->setDropIndicatorShown(true);
ui->NotPossibleList->setSelectionMode(QAbstractItemView::SingleSelection);
ui->NotPossibleList->setDragEnabled(true);
ui->NotPossibleList->viewport()->setAcceptDrops(true);
ui->NotPossibleList->setDropIndicatorShown(true);
ui->NotPossibleList->setDragDropMode(QAbstractItemView::DragDrop);

MODEL *model2 = new MODEL();
model2->setPlayers(QList<int>());
ui->PresentList->setModel(model2);
ui->PresentList->setAcceptDrops(true);
ui->PresentList->setDragDropMode(QAbstractItemView::InternalMove);
ui->PresentList->setDropIndicatorShown(true);
ui->PresentList->setSelectionMode(QAbstractItemView::SingleSelection);
ui->PresentList->setDragEnabled(true);
ui->PresentList->viewport()->setAcceptDrops(true);
ui->PresentList->setDropIndicatorShown(true);
ui->PresentList->setDragDropMode(QAbstractItemView::DragDrop);@

The implementation of the model.

@#include "model.h"

MODEL::MODEL()
{
manager = MANAGER::getInstance();
}

int MODEL::rowCount(const QModelIndex &parent) const
{
return parent.isValid() ? 0 : players.size();
}

QVariant MODEL::data(const QModelIndex &index, int role) const
{
if (!index.isValid() ||
index.row() < 0 || index.row() >= players.size() ||
index.column() < 0 || index.column() >= 1)
return QVariant();

if (role == Qt::DisplayRole && index.column() == 0)
{
    return manager->getPlayer(players[index.row()])->name();
}

return QVariant();

}

bool MODEL::setData(const QModelIndex &index, const QVariant &value, int role)
{
if (!index.isValid() ||
index.row() < 0 || index.row() >= players.size() ||
index.column() < 0 || index.column() >= 1)
return false;

if (role == Qt::UserRole)
{
    players.insert(index.row(), value.toInt());
}

emit dataChanged(index, index);
return true;

}

QVariant MODEL::headerData(int section, Qt::Orientation orientation, int role) const
{
if (role != Qt::DisplayRole)
return QVariant();

if (orientation == Qt::Horizontal && section >= 1)
{
    return tr("Player");
}

return QVariant();

}

Qt::ItemFlags MODEL::flags(const QModelIndex &index) const
{
Qt::ItemFlags defaultFlags = Qt::ItemIsSelectable | Qt::ItemIsEnabled;

if (index.isValid())
    return Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled | defaultFlags;
else
    return Qt::ItemIsDropEnabled | defaultFlags;

}

QStringList MODEL::mimeTypes()
{
QStringList types;
types << "application/vnd.text.list";
return types;
}

QMimeData* MODEL::mimeData(const QModelIndexList &indexes) const
{
QMimeData *mimeData = new QMimeData();
QByteArray encodedData;

QDataStream stream(&encodedData, QIODevice::WriteOnly);

foreach (const QModelIndex &index, indexes) {
    if (index.isValid())
    {
        QString text = data(index, Qt::UserRole).toString();
        stream << text;
    }
}

mimeData->setData("application/vnd.text.list", encodedData);
return mimeData;

}

bool MODEL::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
if (action == Qt::IgnoreAction)
return true;

if (!data->hasFormat("application/vnd.text.list"))
    return false;

if (column > 0)
    return false;

int beginRow;

if (row != -1)
    beginRow = row;
else if (parent.isValid())
    beginRow = parent.row();
else
    beginRow = rowCount(QModelIndex());

QByteArray encodedData = data->data("application/vnd.text.list");
QDataStream stream(&encodedData, QIODevice::ReadOnly);
QStringList newItems;
int rows = 0;

while (!stream.atEnd())
{
    QString text;
    stream >> text;
    newItems << text;
    ++rows;
}

insertRows(beginRow, rows, QModelIndex());
foreach (const QString &text, newItems)
{
    QModelIndex idx = index(beginRow, 0, QModelIndex());
    setData(idx, text, Qt::UserRole);
    beginRow++;
}

return true;

}

Qt::DropActions MODEL::supportedDropActions()
{
return Qt::CopyAction | Qt::MoveAction;
}

void MODEL::setPlayers(QList<int> players)
{
this->players = players;
}

QList<int> MODEL::getPlayers()
{
return players;
}
@

Is there any thing which I forgot to implement or failed to implement?

[digga]

Sorry, that I have to push it up again, but I am still stuck at this problem. My actual code looks like this:
@

MODEL::MODEL()
{
manager = MANAGER::getInstance();
}

int MODEL::rowCount(const QModelIndex &parent) const
{
return parent.isValid() ? 0 : list.size();
}

QVariant MODEL::data(const QModelIndex &index, int role) const
{
if (!index.isValid() ||
index.row() < 0 || index.row() >= list.size() ||
index.column() < 0 || index.column() >= 1)
return QVariant();

if (role == Qt::DisplayRole && index.column() == 0)
{
    return manager->findEntry(list[index.row()])->getName();
}

return QVariant();

}

bool MODEL::setData(const QModelIndex &index, const QVariant &value, int role)
{
if (!index.isValid() ||
index.row() < 0 || index.row() >= list.size() ||
index.column() < 0 || index.column() >= 1)
return false;

if (role == Qt::UserRole)
{
    list[index.row()] = value.toInt();
}

emit dataChanged(index, index);
return true;

}

QVariant MODEL::headerData(int section, Qt::Orientation orientation, int role) const
{

return QVariant();

}

bool MODEL::insertRows(int row, int count, const QModelIndex &parent)
{
beginInsertRows(QModelIndex(), row, row + count - 1);

for (int i = 0; i < count; i++)
{
    list.insert(row, -1);
}

endInsertRows();
return true;

}

bool MODEL::removeRows(int row, int count, const QModelIndex &parent)
{
beginRemoveRows(QModelIndex(), row, row + count - 1);

for (int i = 0; i < count; i++)
{
    list.removeAt(row);
}

endRemoveRows();
return true;

}

Qt::ItemFlags MODEL::flags(const QModelIndex &index) const
{
Qt::ItemFlags defaultFlags = Qt::ItemIsSelectable | Qt::ItemIsEnabled;

if (index.isValid())
    return Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled | defaultFlags;
else
    return Qt::ItemIsDropEnabled | defaultFlags;

}

QStringList MODEL::mimeTypes()
{
QStringList types;
types << "application/vnd.text.list";
return types;
}

QMimeData* MODEL::mimeData(const QModelIndexList &indexes) const
{
QMimeData *mimeData = new QMimeData();
QByteArray encodedData;

QDataStream stream(&encodedData, QIODevice::WriteOnly);

foreach (const QModelIndex &index, indexes) {
    if (index.isValid())
    {
        QString text = data(index, Qt::DisplayRole).toString();
        stream << text;
    }
}

mimeData->setData("application/vnd.text.list", encodedData);
return mimeData;

}

bool MODEL::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
if (action == Qt::IgnoreAction)
return true;

if (!data->hasFormat("application/vnd.text.list"))
    return false;

if (column > 0)
    return false;

int beginRow;

if (row != -1)
    beginRow = row;
else if (parent.isValid())
    beginRow = parent.row();
else
    beginRow = rowCount(QModelIndex());

QByteArray encodedData = data->data("application/vnd.text.list");
QDataStream stream(&encodedData, QIODevice::ReadOnly);
QStringList newItems;
int rows = 0;

while (!stream.atEnd())
{
    QString text;
    stream >> text;
    newItems << text;
    ++rows;
}

insertRows(beginRow, rows, QModelIndex());
foreach (const QString &text, newItems)
{
    QModelIndex idx = index(beginRow, 0, QModelIndex());
    setData(idx, text, Qt::UserRole);
    beginRow++;
}

return true;

}

Qt::DropActions MODEL::supportedDropActions() const
{
return Qt::MoveAction;
}

void MODEL::setList(QList<int> list)
{
this->list = list;
}

QList<int> MODEL::getList()
{
return list;
}
@

In my mainwindow.cpp
@ MODEL*model = new MODEL();
model->setPlayers(list);
ui->NotPossibleList->setModel(model);
ui->NotPossibleList->setSelectionMode(QAbstractItemView::ExtendedSelection);
ui->NotPossibleList->setDragEnabled(true);
ui->NotPossibleList->setAcceptDrops(true);
ui->NotPossibleList->setDropIndicatorShown(true);
@