Editable QComboBox with QItemDelegate

[Jmgr]

Hi all :)

I am trying to customize my QTreeView to get an editable QComboBox into a column.
There are some example on the Net, but I haven't seen any with an editable QComboBox, and mine does not work properly...

Let me explain : if I click into the cell and select an item from the list it works : the selection is saved. But if I enter free text and change the focus, then the text is lost, and my DisplayRole role contains nothing. But if I enter some text again, then it will be saved...

I searched without success some hours but didn't find any clue, so I'm posting here, maybe someone has a good idea about this...

Now, some code :

QWidget *ActionDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
QComboBox *comboBox = new QComboBox(parent);
comboBox->setEditable(true);
comboBox->setInsertPolicy(QComboBox::NoInsert);
comboBox->addItems(index.model()->data(index, CustomRoles::ValueRole).toStringList());

connect(comboBox, SIGNAL(activated(int)), this, SLOT(emitCommitData()));
connect(comboBox->lineEdit(), SIGNAL(editingFinished()), this, SLOT(emitCommitData()));

QString currentText = index.model()->data(index, Qt::DisplayRole).toString();
int selectedItem = comboBox->findText(currentText);
if(selectedItem == -1)
comboBox->setEditText(index.model()->data(index, Qt::DisplayRole).toString());
else
comboBox->setCurrentIndex(selectedItem);

return comboBox;
}


void ActionDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
QComboBox *comboBox = qobject_cast<QComboBox*>(editor);

comboBox->clear();
comboBox->addItems(index.model()->data(index, CustomRoles::ValueRole).toStringList());

QString currentText = index.model()->data(index, Qt::DisplayRole).toString();
int selectedItem = comboBox->findText(currentText);
if(selectedItem == -1)
comboBox->setEditText(index.model()->data(index, Qt::DisplayRole).toString());
else
comboBox->setCurrentIndex(selectedItem);
}


void ActionDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
QComboBox* comboBox = qobject_cast<QComboBox*>(editor);

QStringList value;
for(int i=0;i<comboBox->count();++i)
value.append(comboBox->itemText(i));

int selectedItem = comboBox->findText(comboBox->currentText());
if(selectedItem == -1)
{
model->setData(index, -1, CustomRoles::SelectedItemRole);
model->setData(index, comboBox->currentText(), Qt::DisplayRole);
}
else
{
model->setData(index, selectedItem, CustomRoles::SelectedItemRole);
model->setData(index, comboBox->itemText(selectedItem), Qt::DisplayRole);
}

model->setData(index, value, CustomRoles::ValueRole);
}


void ActionDelegate::emitCommitData()
{
emit commitData(qobject_cast<QWidget *>(sender()));
}


CustomRoles::SelectedItemRole represents the currently selected item, or -1 if it's free text
CustomRoles::ValueRole represents all the items of the combo box

[wysota]

You have to play a bit with event filters, so that for example when you focus out of the editor or when you press the enter key, the contents is saved into the model.

[Jmgr]

But why does
connect(comboBox->lineEdit(), SIGNAL(editingFinished()), this, SLOT(emitCommitData())); not save the data from the QLineEdit ?

I also noticed that setEditorData is called twice after an edition...

[wysota]

What is emitCommitData()? Is it a slot? The line edit is not the editor widget, but part of it, so your emitCommitData() doesn't make much sense.

[Jmgr]

Well, as I posted on the first post it's a slot which calls

emit commitData(qobject_cast<QWidget *>(sender()));

EDIT : Yes, it's a slot :)

[wysota]

Yeah, but it doesn't make much sense, as the line edit is not the editor.

[Jmgr]

Huh, that is true :)

Ok, I will look how to use the event filter.

[Jmgr]

It is probably a noobish question, but how do I installEventFilter within createEditor, because since createEditor is const, calling myLineEdit->installEventFilter(this) produces an error...

I doesn't know why it is so complicated to put a simple QComboBox into a cell :confused:

Anyway, I tested with having persistent editors : it seems to work, but the method of showing an editor when needed is much better...

[wysota]

You have to cheat using const_cast(). You can take a look at the implementation of QItemDelegate and the factory class it uses to see how it is internally implemented. With all the event filters and stuff.

[Jmgr]

I will look at it, thanks :)

[faraslacks]

Excuse me, may be it's easy, but what is CustomRoles?

[wysota]

Excuse me, may be it's easy, but what is CustomRoles?

Custom item roles in ItemViews