Editable QComboBox with QItemDelegate

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 :

Code:

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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;
}

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Code:

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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);
}

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Code:

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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);
}

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Code:

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

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

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.

But why does

Code:

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

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not save the data from the QLineEdit ?

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

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.

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

Code:

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

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EDIT : Yes, it's a slot :)

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

Huh, that is true :)

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

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...

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.

I will look at it, thanks :)

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

Quote:

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Originally Posted by faraslacks

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

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[WIKI=QAbstractItemModel#Custom_item_roles]Custom item roles in ItemViews[/WIKI]