Combo Boxes in Item Views

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Revision as of 08:52, 5 December 2018 by VRonin (talk | contribs) (Checking index.column() in the delegate is bad design as it ties the delegate to a specific model, setItemDelegateForColumn should be used instead)

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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
{
    // 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
{
    QComboBox* cb = qobject_cast<QComboBox*>(editor);
    Q_ASSERT(cb);
    // 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);
}


void ComboBoxItemDelegate::setModelData(QWidget* editor, QAbstractItemModel* model, const QModelIndex& index) const
{
    QComboBox* cb = qobject_cast<QComboBox*>(editor);
    Q_ASSERT(cb);
    model->setData(index, cb->currentText(), Qt::EditRole);
}


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);
    // ComboBox ony in column 2 
    tw.setItemDelegateForColumn(1, cbid);
    tw.setColumnCount(4);
    tw.setRowCount(10);
    tw.resize(600,400);
    tw.show();

    return a.exec();
}