CODEWITHSUNDEEP
qtqt5qtreeview
Ender
Ender

Reputation: 1778

How to immediately detect checkbox state change in a QTreeView?

I'm using Qt 5.9 on linux. I have a QTreeView where I set a custom model which is derived from QAbstractItemModel and I fill the tree with several plain classes for the tree items. Each treeview item has a checkbox next to it.

I have the following attribute set on the QTreeView ...

treeView->viewport()->setAttribute(Qt::WA_Hover);

so that when the mouse hovers over a tree item, I can capture the event via my delegates paint method.

The problem is that I also have a checkbox in each tree item and I'd like to be able to capture when the state of the checkbox changes, but my delegate doesn't seem to capture that. I can tell what state the checkbox is in when I hover the mouse over the item, but what I want is to be able to immediately know when the state of the checkbox changes w/o having to move the mouse any further.

Any thoughts on how to immediately detect when the state of the checkbox changes in a tree item?

Upvotes: 1

Views: 1216

Answers (1)

eyllanesc
eyllanesc

Reputation: 243907

A possible solution is to track the state change of the checkbox using the editorEvent method:

#include <QtWidgets>

class CheckboxDelegate: public QStyledItemDelegate{
    Q_OBJECT
public:
    using QStyledItemDelegate::QStyledItemDelegate;
    bool editorEvent(QEvent *event,
                     QAbstractItemModel *model,
                     const QStyleOptionViewItem &option,
                     const QModelIndex &index) override
    {
        Qt::CheckState last = static_cast<Qt::CheckState>(model->data(index, Qt::CheckStateRole).toInt());
        bool res = QStyledItemDelegate::editorEvent(event, model, option, index);
        Qt::CheckState current = static_cast<Qt::CheckState>(model->data(index, Qt::CheckStateRole).toInt());
        if(last != current)
            Q_EMIT stateChanged(index);
        return  res;
    }
Q_SIGNALS:
    void stateChanged(const QModelIndex & index);
};
#include "main.moc"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QStandardItemModel model;
    model.setColumnCount(2);
    for(int i=0; i<4; ++i){
        QList<QStandardItem *> l;
        for (int c=0; c< model.columnCount(); ++c) {
            QStandardItem *parent = new QStandardItem(QString("%1-%2").arg(i).arg(c));
            parent->setCheckable(true);
            l << parent;
            for (int j=0; j<4; ++j) {
                QList<QStandardItem *> ll;
                for (int c=0; c< model.columnCount(); ++c) {
                    QStandardItem *child  = new QStandardItem(QString("%1-%2-%3").arg(i).arg(j).arg(c));
                    child->setCheckable(true);
                    ll << child;
                }
                parent->appendRow(ll);
            }
        }
        model.appendRow(l);
    }
    QTreeView w;
    w.viewport()->setAttribute(Qt::WA_Hover);
    CheckboxDelegate *delegate = new CheckboxDelegate(&w);
    w.setItemDelegate(delegate);
    QObject::connect(delegate, &CheckboxDelegate::stateChanged, [](const QModelIndex & index){
        QString text = index.data().toString();
        Qt::CheckState state = static_cast<Qt::CheckState>(index.data(Qt::CheckStateRole).toInt());
        qDebug() << text << state;
    });
    w.setModel(&model);
    w.resize(640, 480);
    w.expandAll();
    w.show();
    return a.exec();
}

Upvotes: 2

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