Calling a Dialog from a ComboBox in a QStyledItemDelegate

So what I have here is my delegate code for a QAbstractTableModel. The 2nd column (index = 1), is always a comboBox. That comboBox has a list of actions that a given Unit in my simulation can perform. Upon clicking certain actions like Build or Train, I want a Dialog to pop up giving the user a set of choices. After making there choice, the delegate is supposed to update the model's data and move on.

Here is the snag I've run into. If I try to call a dialog from setModelData(), setEditorData(), those functions are const so I can't assign the r开发者_如何学Goesults of the dialog to anything.

What I have tried to do is to connect the signal indexChanged(QString) from the QComboBox created in createEditor(). This at least allowed me to assign the result and call the dialog only when the appropriate choice was made. However I keep getting a seggy fault and the trace in QTCreator will not land on C code (33 calls of assembly). I'm unsure as to why I got that seggy.

When I tried that approach, the table no longer had the combobox once the dialog appeared. It reverted to its previous state and as soon as the program left the slot I made for QComboBox::indexChanged(QString), the seggy happened.

DelegateAction.h

#ifndef DELEGATEACTION_H
#define DELEGATEACTION_H

#include <QVariant>
#include <QStyledItemDelegate>
#include <QString>

#include <QApplication>
#include <QWidget>
#include <QLabel>
#include <QComboBox>
#include <QProgressBar>
#include <QMouseEvent>

#include <JECMessageTable.h>

#include <UnitBase.h>
#include <ModelListUnit.h>

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

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

public slots:
    void setUnits(QList<Unit*>* units);

protected:
    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const;
    //bool editorEvent(QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option, const QModelIndex &index);
private slots:
    void comboChanged(QString string);
    void comboDestroyed();

private:
    bool comboUpdated;
    const UnitBase* selectedUnit;
    ModelListUnit *model;           // The model for the JECMessageTable.

    QList<Unit*>* units;     // The current list of units.

};

#endif // DELEGATEACTION_H

DelegateAction.cpp

#include "DelegateAction.h"

DelegateAction::DelegateAction(QObject *parent) :
    QStyledItemDelegate(parent),
    selectedUnit(0),
    model(0)
{
}

DelegateAction::~DelegateAction()
{
    delete model;
}

QWidget * DelegateAction::createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    QWidget* editor = 0;

    switch (index.column())
    {
    case 0:
    default:
    {
        editor = new QLabel();
        break;
    }
    case 1:
    {
        QComboBox* combo = new QComboBox(parent);
        combo->addItem("Idle");
        combo->addItem("Gather");
        combo->addItem("Train");
        combo->addItem("Build");
        combo->addItem("Upgrade");
        editor = combo;
//        connect(combo, SIGNAL(currentIndexChanged(QString)), this, SLOT(comboChanged(QString)));
//        connect(combo, SIGNAL(destroyed()), this, SLOT(comboDestroyed()));
        break;
    }
    case 4:
    {
        editor = new QProgressBar(parent);
        break;
    }
    }

    editor->installEventFilter(const_cast<DelegateAction*>(this));
    return editor;
}

void DelegateAction::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    QVariant value = index.model()->data(index, Qt::DisplayRole);

    switch (index.column())
    {
    case 0:
    default:
    {
        QLabel* label = static_cast<QLabel*>(editor);
        label->setText(value.toString());
        break;
    }
    case 1:
    {
        QComboBox* combo = static_cast<QComboBox*>(editor);
        combo->setCurrentIndex(combo->findText(value.toString()));

        break;
    }
    case 4:
    {
        QProgressBar* progress = static_cast<QProgressBar*>(editor);
        progress->setValue(value.toInt());
        break;
    }
    }

}

void DelegateAction::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{
    QVariant value;
    switch (index.column())
    {
    case 0:
    default:
    {
        value = static_cast<QLabel*>(editor)->text();
        break;
    }
    case 1:
    {
        QString string = static_cast<QComboBox*>(editor)->currentText();

        switch (Action::getType(string))
        {
        case Action::INVALID:
        {
            return;
        }
        case Action::IDLE:
        {
            return;
        }
        case Action::GATHER:
        {
            return;
        }
        case Action::BUILD:
        {
            return;
        }
        case Action::TRAIN:
        {
            // Summon the build choice dialog.
            if (units == 0)
            {
                return;
            }

            JECMessageTable messageBox(this->model, "Test");
            messageBox.exec();

            if (messageBox.result() == QDialog::Accepted)
            {
                //selectedUnit = this->model->getSelectedUnit();
            }
            else
            {
               //selectedUnit = 0;
            }

            return;
        }
        case Action::MORPH:
        {
            return;
        }
        case Action::UPGRADE:
        {

        }
        }

        break;
    }
    case 4:
    {
        value = static_cast<QProgressBar*>(editor)->value();
        break;
    }
    }

    model->setData(index, value);
}

void DelegateAction::updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    editor->setGeometry(option.rect);
}

QSize DelegateAction::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{
    if (index.column() == 4)
    {
        return QSize(option.rect.width(), option.rect.height());
    }
    else
    {
        return QStyledItemDelegate::sizeHint(option, index);
    }
}

void DelegateAction::paint(QPainter *painter, const QStyleOptionViewItem &item, const QModelIndex &index) const
{
    if (index.column() == 4 && index.isValid() == true)
    {
        QStyleOptionProgressBarV2 progress;

        progress.minimum = 0;
        progress.maximum = 100;
        progress.progress = index.data().toInt();
        progress.rect = QRect(item.rect.x(), item.rect.y(), item.rect.width(), item.rect.height());

        QApplication::style()->drawControl(QStyle::CE_ProgressBar, &progress, painter);
    }
    else
    {
        // Painting the cells normally.
        QStyledItemDelegate::paint(painter, item, index);
    }
}

void DelegateAction::setUnits(QList<Unit*> *units)
{
    this->units = units;

    if (units != 0)
    {
        if (units->length() > 0)
        {
            model = new ModelListUnit(&units->at(0)->getUnitBase()->getOptionUnit());
        }
    }
}

void DelegateAction::comboChanged(QString string)
{

//    comboUpdated = true;
//    switch (Action::getType(string))
//    {
//    case Action::INVALID:
//    {
//        return;
//    }
//    case Action::IDLE:
//    {
//        return;
//    }
//    case Action::GATHER:
//    {
//        return;
//    }
//    case Action::BUILD:
//    {
//        return;
//    }
//    case Action::TRAIN:
//    {
//        // Summon the build choice dialog.
//        if (units == 0)
//        {
//            return;
//        }

//        JECMessageTable messageBox(model, "Test");
//        messageBox.exec();

//        if (messageBox.result() == QDialog::Accepted)
//        {
//            selectedUnit = model->getSelectedUnit();
//        }
//        else
//        {
//            selectedUnit = 0;
//        }

//        return;
//    }
//    case Action::MORPH:
//    {
//        return;
//    }
//    case Action::UPGRADE:
//    {

//    }
//    }

}

void DelegateAction::comboDestroyed()
{
    disconnect(this, SLOT(comboChanged(QString)));
    disconnect(this, SLOT(comboDestroyed()));
}

//bool DelegateAction::editorEvent(QEvent *event, QAbstractItemModel *model, const QStyleOptionViewItem &option, const QModelIndex &index)
//{
//    QStyledItemDelegate::editorEvent(event, model, option, index);

//    if (comboUpdated == true && index.isValid() == true)
//    {
//        comboUpdated = false;

//        if (selectedUnit != 0)
//        {
//            units->at(index.row());
//        }
//    }
//}

---

I figured this out. If anyone is interested in something similar, I sub classed QTableView.

Inside QTableView i used QTableView::setIndexWidget() to use QComboBoxes and QProgressBars. Basically my subclass had a QList of both types of widgets and they corresponded to a particular row in the table.

---

1. derive ComboBoxEditor from QComboBox
2. keep a Action object in ComboBoxEditor (data stored in model index)
3. when delegate's comboChanged() is called, you can access the Action via sender(), that is ComboBoxEditor.

Please refer to the official example, StarDelegate.

http://doc.qt.io/qt-5/qtwidgets-itemviews-stardelegate-example.html