Combo Boxes in Item Views

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Sample code to use combo boxes as editor widgets in an item view or item widget.

The delegate creates a combo box if the index is in the second column of a list view. For the other columns it just returns the default editor, that QStyledItemDelegate creates.

File itemdelegate.h

#ifndef ITEMDELEGATE_H
#define ITEMDELEGATE_H

#include <QStyledItemDelegate>

class ComboBoxItemDelegate : public QStyledItemDelegate
{
    Q_OBJECT
public:
    ComboBoxItemDelegate(QObject* parent=0);
    ~ComboBoxItemDelegate();

    virtual QWidget* createEditor(QWidget* parent, const QStyleOptionViewItem& option, const QModelIndex& index) const;
    virtual void setEditorData(QWidget* editor, const QModelIndex& index) const;
    virtual void setModelData(QWidget* editor, QAbstractItemModel* model, const QModelIndex& index) const;
};

#endif // ITEMDELEGATE_H

File itemdelegate.cpp

#include "itemdelegate.h"
#include <QComboBox>

ComboBoxItemDelegate::ComboBoxItemDelegate(QObject* parent)
    : QStyledItemDelegate(parent)
{
}


ComboBoxItemDelegate::~ComboBoxItemDelegate()
{
}


QWidget* ComboBoxItemDelegate::createEditor(QWidget* parent, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
    // ComboBox ony in column 2
    if (index.column() != 1)
        return QStyledItemDelegate::createEditor(parent, option, index);

    // Create the combobox and populate it
    QComboBox* cb = new QComboBox(parent);
    int row = index.row();
    cb->addItem(QString("one in row %1").arg(row));
    cb->addItem(QString("two in row %1").arg(row));
    cb->addItem(QString("three in row %1").arg(row));
    return cb;
}


void ComboBoxItemDelegate::setEditorData(QWidget* editor, const QModelIndex& index) const
{
    if (QComboBox* cb = qobject_cast<QComboBox*>(editor)) {
       // get the index of the text in the combobox that matches the current value of the itenm
       QString currentText = index.data(Qt::EditRole).toString();
       int cbIndex = cb->findText(currentText);
       // if it is valid, adjust the combobox
       if (cbIndex >= 0)
           cb->setCurrentIndex(cbIndex);
    } else {
        QStyledItemDelegate::setEditorData(editor, index);
    }
}


void ComboBoxItemDelegate::setModelData(QWidget* editor, QAbstractItemModel* model, const QModelIndex& index) const
{
    if (QComboBox* cb = qobject_cast<QComboBox*>(editor))
        // save the current text of the combo box as the current value of the item
        model->setData(index, cb->currentText(), Qt::EditRole);
    else
        QStyledItemDelegate::setModelData(editor, model, index);
}

File main.cpp

#include <QApplication>
#include <QTableWidget>

#include "itemdelegate.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QTableWidget tw;

    ComboBoxItemDelegate* cbid = new ComboBoxItemDelegate(&tw);
    tw.setItemDelegate(cbid);
    tw.setColumnCount(4);
    tw.setRowCount(10);
    tw.resize(600,400);
    tw.show();

    return a.exec();
}