Add QCombobox inside QTreeview specific cell - c++

Question

I was trying to insert a QCombobox only in some specific cells of my QTreeview. As I read, I think that I need to create my delegate (that I've created). But I don't understand how to insert this in my treeview.
I want to realize this:
This is my code:
#include <QTreeView>
#include <QStandardItemModel>
#include <QStandardItem>
#include "mainwindow.h"
#include "comboboxdelegate.h"
const int ROWS = 2;
const int COLUMNS = 3;
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
treeView = new QTreeView(this);
setCentralWidget(treeView);
standardModel = new QStandardItemModel ;
standardModel->setColumnCount(2);
QStandardItem *root = new QStandardItem("ROOT");
root->setCheckable(true);
root->setCheckState(Qt::Checked);
root->setEditable(false);
standardModel->setItem(0, 0, root);
QList< QStandardItem * > listOne ;
QStandardItem *f1 = new QStandardItem( "Field_1" );
f1->setCheckable(true);
f1->setCheckState(Qt::Checked);
f1->setEditable(false);
listOne.append(f1) ;
listOne.append( new QStandardItem( "<Free text>" ) ) ;
root->appendRow(listOne);
QList< QStandardItem * > listTwo ;
QStandardItem *f2 = new QStandardItem( "Field_2" );
listTwo.append(f2) ;
listTwo.append( new QStandardItem( "<HERE COMBOBOX!>" ) ) ;
root->appendRow(listTwo);
treeView->setModel(standardModel);
treeView->expandAll();
}
I managed to create an entire column with QCombobox (using custom delegate). But I don't know how to set only specific cell. Anyone can help me?

Answer 1

QTreeWidget makes widget items convenient.
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
treeWidget = new QTreeWidget(this);
setCentralWidget(treeWidget);
treeWidget->setColumnCount(2);
auto root = new QTreeWidgetItem({"Root"});
root->setCheckState(0, Qt::Checked);
treeWidget->addTopLevelItem(root);
auto child1 = new QTreeWidgetItem({"Field 1", "<Free Text>"});
child1->setCheckState(0, Qt::Checked);
child1->setFlags(child1->flags() | Qt::ItemIsEditable);
root->addChild(child1);
auto child2 = new QTreeWidgetItem({"Field 2"});
child2->setFlags(child2->flags() | Qt::ItemIsEditable);
root->addChild(child2);
auto comboBox = new QComboBox();
comboBox->addItems({"Red", "Blue", "Yellow"});
treeWidget->setItemWidget(child2, 1, comboBox);
connect(treeWidget, &QTreeWidget::itemDoubleClicked, treeWidget, &QTreeWidget::editItem);
treeWidget->expandAll();
}
There are a few differences to note.
You'll need QTreeWidget* treeWidget; in your class declaration. And include the QTreeWidget header.
By default, TreeWidgetItems aren't checkable (no checkbox), but calling QTreeWidgetItem::setCheckState with Qt::Checked or Qt::Unchecked will make it checkable.
Items are not editable by default. Whole rows can be made editable by calling treeWidgetItem->setFlags(treeWidgetItem->flags() | Qt::ItemIsEditable). To filter what rows/columns can be edited, you can define your own itemDoubleClicked slot and use an if-statement (example).

Answer 2

You need to store combobox items in model item, for example using Qt::UserRole
QStringList options = {"one", "two", "three"};
QStandardItem* item = new QStandardItem(options[0]);
item->setData(QVariant(options),Qt::UserRole);
listTwo.append(item);
Then you need assign delegate to view. You can assign it for the whole table and return default delegate if index.data(Qt::UserRole).isNull().
Delegate* delegate = new Delegate(treeView);
treeView->setItemDelegate(delegate);
It's probably a good idea to set edit triggers to all, so dropdown occurs not only on doubleclick but also on single click
treeView->setEditTriggers(QAbstractItemView::AllEditTriggers);
Delegate must implement createEditor, setEditorData and setModelData
QWidget *Delegate::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
if (index.data(Qt::UserRole).isNull()) {
return QStyledItemDelegate::createEditor(parent, option, index);
}
return new QComboBox(parent);
}
void Delegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
QComboBox* comboBox = qobject_cast<QComboBox*>(editor);
if (!comboBox) {
return QStyledItemDelegate::setEditorData(editor, index);
}
QStringList options = index.data(Qt::UserRole).toStringList();
comboBox->addItems(options);
QString value = index.data().toString();
int current = options.indexOf(value);
if (current > -1) {
comboBox->setCurrentIndex(current);
}
comboBox->showPopup();
}
void Delegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
QComboBox* comboBox = qobject_cast<QComboBox*>(editor);
if (!comboBox) {
return QStyledItemDelegate::setModelData(editor, model, index);
}
model->setData(index, comboBox->currentText());
}
By default delegate doesn't change how item is displayed and show editor only if edit is triggered: no combobox is shown. But you can override it with custom paintEvent.
void Delegate::paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
if (index.data(Qt::UserRole).isNull()) {
return QStyledItemDelegate::paint(painter, option, index);
}
QStyle* style = qApp->style();
QStyleOptionComboBox opt;
opt.rect = option.rect;
opt.currentText = index.data().toString();
opt.palette = option.palette;
opt.state = option.state;
opt.subControls = QStyle::SC_All;
opt.activeSubControls = QStyle::SC_All;
opt.editable = false;
opt.frame = true;
style->drawComplexControl(QStyle::CC_ComboBox, &opt, painter, 0);
style->drawControl(QStyle::CE_ComboBoxLabel, &opt, painter, 0);
}
Full source here: combobox-delegate