How to implement checkstate for QAbstractItemModel or QAbstractListModel

[milan]

Hello, I have success implementing some methods of QAbstractListModel. How can I add checkstate to the listed items in the model. The model is used by QListView.

#include "intmodel.h"

IntModel::IntModel(int count,  QObject *parent) : QAbstractListModel(parent)
{
    for (int i=0; i < count; ++i)
        m_values << i+1;
}

int IntModel::rowCount(const QModelIndex &parent) const
{
    if (parent.isValid())
        return 0;
    return  m_values.count();
}

QVariant IntModel::data(const QModelIndex &index, int role) const
{
    if (!index.isValid())
        return QVariant();

    if(role != Qt::DisplayRole && role != Qt::CheckStateRole) {// && role != Qt::EditRole )
        return QVariant();
    }

    if((role == Qt::DisplayRole) && (index.column() == 0 && index.row() < m_values.count()))
        return m_values.at( index.row() );
    else
        return QVariant();

}

Qt::ItemFlags IntModel::flags( const QModelIndex &index ) const
{
    if(!index.isValid())
        return Qt::ItemIsEnabled;
    return Qt::ItemIsSelectable | Qt::ItemIsEditable | Qt::ItemIsEnabled | Qt::ItemIsUserCheckable;
}

bool IntModel::setData( const QModelIndex &index, const QVariant &value, int role )
{
    qDebug() << "IntModel setData: " << role;
    if((role != Qt::EditRole && role != Qt::CheckStateRole) || index.column() != 0 || index.row() >= m_values.count())
        return false;

    if(role == Qt::EditRole) {
        if(value.toInt() == m_values.at( index.row()))
            return false;
        m_values[index.row()] = value.toInt();
        emit dataChanged(index, index);
        return true;
    }
    else if (role == Qt::CheckStateRole) {
		// TO DO
    }
}

#ifndef INTMODEL_H
#define INTMODEL_H

#include <QAbstractListModel>
#include <QDebug>

class IntModel : public QAbstractListModel
{
    Q_OBJECT

public:
    explicit IntModel(int count, QObject *parent = nullptr);

    // Basic functionality:
    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;

    Qt::ItemFlags flags(const QModelIndex &index) const override;
    bool setData(const QModelIndex &index, const QVariant &value, int role) override;
private:
    QList<int> m_values;
};

#endif // INTMODEL_H

[raven-worx]

@milan
here is an example: http://programmingexamples.net/wiki/Qt/ModelView/AbstractTableModelCheckable

[milan]

@raven-worx . Thanks for your response. Yes I have seen this example. I would like to implement it without the need for Item class? But I do not know if it is possible?

[raven-worx]

@milan
well you need to store the checkstate along with your model data/entries. There is no way around.

For example instead of a QList<int> you could use a QList<QPair<int,Qt::CheckState> > for example, or any other custom struct (instead of QPair)

[milan]

@raven-worx . Thanks. Is it possible to use QList<QStandardItem> instead? or QList<QVariant> or neither?

[raven-worx]

@milan said in How to implement checkstate for QAbstractItemModel or QAbstractListModel:

Is it possible to use QList<QStandardItem> instead?

doesn't make much sense.

@milan:

or QList<QVariant> or neither?

since a QVariant can hold any type of data yes, if you like so.
But still you will need to create a custom struct, register it's metatype and put it into a QVariant.

[milan]

@raven-worx. I tried with example you mentioned at http://programmingexamples.net/wiki/Qt/ModelView/AbstractTableModelCheckable. But I found, I cannot hide the checkboxes (if needed). Maybe I plan to use this model for other different views too. Maybe another Listview without checkboxes.

[VRonin]

@milan said in How to implement checkstate for QAbstractItemModel or QAbstractListModel:

I cannot hide the checkboxes

if you return QVariant() for the CheckStateRole the checkbox will not appear in the default delegate (QStyledItemDelegate)