How to repaint QWidget encapsulated in QDeclarativeItem in QML? - c++

Question

I work in a C++/QML environment and I use Qt 4.8 with QtQuick 1.0.
I have a QWidget derivated class, QCustomPlot, and I encapsulated it in a custom QDeclarativeItem derived class. I use a QGraphicsProxyWidget to embed the QWidget, and it appears nicely upon creation. I would like to update the chart periodically, but I simply cannot, no matter what I do it stays however I initiated it in the constructor.
Here is the code (somewhat simplified) I have:
flowgrafik.h:
class FlowGrafik : public QDeclarativeItem
{
Q_OBJECT
public:
explicit FlowGrafik(QDeclarativeItem *parent = 0);
~FlowGrafik();
void addFlow(double flow);
signals:
public slots:
private:
QCustomPlot * customPlot;
QGraphicsProxyWidget * proxy;
QVector<double> x, y;
};
flowgrafik.cpp:
FlowGrafik::FlowGrafik(QDeclarativeItem *parent) : QDeclarativeItem(parent)
{
customPlot = new QCustomPlot();
proxy = new QGraphicsProxyWidget(this);
proxy->setWidget(customPlot);
this->setFlag(QGraphicsItem::ItemHasNoContents, false);
customPlot->setGeometry(0,0,200,200);
/* WHAT I WRITE HERE WILL BE DISPLAYED */
// pass data points to graph:
customPlot->graph(0)->setData(x, y);
customPlot->replot();
}
FlowGrafik::~FlowGrafik()
{
delete customPlot;
}
void FlowGrafik::addFlow(double flow)
{
//THIS PART DOES NOT GET DISPLAYED
for (int i=0; i<99; ++i)
{
y[i] = y[i+1];
}
y[99] = flow;
customPlot->graph(0)->setData(x, y);
customPlot->replot();
this->update();
}
mainview.qml:
Rectangle {
id: flowGrafik
objectName: "flowGrafik"
x: 400
y: 40
width: 200
height: 200
radius: 10
FlowGrafik {
id: flowGrafikItem
}
}
I would really appreciate if anyone could tell me why my QCustomPlot QWidget does not replot.

Answer 1

Eventually the solution was to create a pointer in the C++ code that points at the QML item.
I accidentally created an other instance in the C++, modified that one, and expected the QML instance to change.
QDeclarativeView mainView;
mainView.setSource(QUrl("qrc:///qml/qml/mainview.qml"));
Flowgrafik * flowGrafik = mainView.rootObject()->findChild<QObject*>(QString("flowGrafikItem"));
//or if Flowgrafik was the main element: Flowgrafik * flowGrafik = mainView.rootObject();
flowGrafik->addFlow(x);