Question

I have this application where the user can draw some custom QGraphicsItems in a QGraphicsView and I would like that some data about those items be also displayed in a QTableWidget.

The code for the custom QGraphicsItem:
header file:

    class Clothoid : public QGraphicsItem
    {
    public:
        Clothoid(QPoint startPoint, QPoint endPoint);
        virtual ~Clothoid();

        QPoint sPoint;
        QPoint ePoint;
        CFloat startCurvature;
        CFloat endCurvature;
        CFloat clothoidLength;
        CFloat tangentAngle;
    ...
    }

cpp file:

    Clothoid::Clothoid(QPoint startPoint, QPoint endPoint)
    {
        sPoint = startPoint;
        ePoint = endPoint;
        startCurvature = 0.0;
        endCurvature = 0.0;
        clothoidLength = sqrt(pow(endPoint.x() - startPoint.x(),2) +
                              pow(endPoint.y() - startPoint.y(),2));
    }

The code for the Graphics view:

    renderArea::renderArea(QWidget *parent):
            QGraphicsView(parent)
    {
        scene = new QGraphicsScene(this);
        scene->setItemIndexMethod(QGraphicsScene::NoIndex);
        scene->setSceneRect(0, 0, 850, 480);
        setScene(scene);
        setCacheMode(CacheBackground);
        setViewportUpdateMode(BoundingRectViewportUpdate);
        setRenderHint(QPainter::Antialiasing);
        setTransformationAnchor(AnchorUnderMouse);
        scale(qreal(1.0), qreal(1.0));
        setMinimumSize(400, 400);
    }

    void renderArea::mousePressEvent(QMouseEvent *event)
    {
        QPoint p = event->pos();

        updateList(p);
    }

    void renderArea::updateList(const QPoint &p)
    {
        Point point;
        point.point = p;
        point.isSelected = false;
        list.append(point);
        if (list.size() > 1)
            updateClothoid(list[list.size()-2].point, list[list.size()-1].point);
    }

    void renderArea::updateClothoid(const QPoint &p1, const QPoint &p2)
    {
        Clothoid *temp = new Clothoid(p1, p2);

        clothoids.append(temp);

        scene->addItem(temp);

        emit clothoidAdded(&clothoids);
    }

where clothoids are defined as:

QList clothoids;

I connect the signal with the slot in another class special for the table widget:

    void TableViewList::onClothoidAdded(QList *clothoids)
    {
        setRowCount(clothoids->size());

        for (int i = 0; i size(); i++){
            setItem(i+1, 0, new QTableWidgetItem(clothoids->at(i)->startCurvature));
            setItem(i+1, 1, new QTableWidgetItem(clothoids->at(i)->endCurvature));
            setItem(i+1, 2, new QTableWidgetItem(clothoids->at(i)->clothoidLength));
            setItem(i+1, 3, new QTableWidgetItem(clothoids->at(i)->sPoint.x() + ", " +
                                               clothoids->at(i)->sPoint.y()));
            setItem(i+1, 4, new QTableWidgetItem(clothoids->at(i)->ePoint.x() + ", " +
                                               clothoids->at(i)->ePoint.y()));
        }

    }

The problem is that the data isn’t inserted in the table. I checked with debugging and I saw that the array holds the wanted data. How could I access it correctly? Any ideas?

When trying with QTableView and QStandardItemModel I encounter this problem: the data in the model is not inserted in the table:

    renderingWidget::renderingWidget(QWidget *parent) :
            QWidget(parent),
            ui(new Ui::renderingWidget)
    {
        ui->setupUi(this);

        model.setColumnCount(3);
        ui->clothoidTable->setModel(&model);

        SpinBoxDelegate delegate;
        ui->clothoidTable->setItemDelegate(&delegate);


        connect (ui->saveButton, SIGNAL(clicked()), this, SLOT(createClothoid()));
    }


    void renderingWidget::createClothoid()
    {
        model.setRowCount(model.rowCount()+1);

        QModelIndex index = model.index(model.rowCount(), 1, QModelIndex());
        model.setData(index, QVariant(ui->lengthSpinBox->value()));
        index = model.index(model.rowCount(), 2, QModelIndex());
        model.setData(index, QVariant(ui->sCurvSpinBox->value()));
        index = model.index(model.rowCount(), 3, QModelIndex());
        model.setData(index, QVariant(ui->eCurvSpinBox->value()));

        ui->clothoidTable->setModel(&model);
    }

I want to be able to insert the data in some text boxes/spin boxes and then on button click the data should be added in the table. But only the number of rows is updated not the data within. Am I doing anything wrong while setting the data for the model?

Answer 1

This is going to be hard to hear, but I’d back away from the QTableWidget convenience class.

Check this link on Qt Model/View Programming out for how Qt is really meant to handle complex tables like yours.

My two cents on Model/Views is this:

1. Use a QTableView instead of a QTableWidget.
2. Subclass QAbstractItemModel and implement data() (for reading), and
   all the other functions you need from the documentation. This is the
   trickiest part, but refer to the above link for a walkthrough of how
   to do this.
3. setModel() of the QTableView to your subclassed model.

If you have more questions, I’ll be happy to answer them.