[SOLVED] QQuickItem change property with animation

Yrchgrchh

Hi All,

I'm trying to create and manipulate QML components from within C++. In test app I simply want to change Rectangle's coordinates and make it animated.
Although I see animation when set y in List's constructor for the first time it crashes in List::move in setProperty("y") if I have 'Behavior on y' in my qml. Furthermore if I comment it out I can't see onYChanged output from Qml. What's wrong with it?

list.h
@#ifndef LIST_H
#define LIST_H

#include <QQuickItem>
#include <QList>

class List : public QQuickItem
{
Q_OBJECT

QList<QQuickItem*> m_items;

public:
explicit List(QQuickItem *parent = 0);

void move(int x, int y);

void keyPressEvent(QKeyEvent *event);

};

#endif // LIST_H@

list.cpp
@#include "list.h"
#include <QQmlEngine>

List::List(QQuickItem *parent) :
QQuickItem(parent)
{
QQmlEngine engine;
QQmlComponent component(&engine, QUrl::fromLocalFile("qml/epg/Cell.qml"));

m_items.append( dynamic_cast<QQuickItem*>(component.create()) );
m_items.back()->setParentItem(this);

m_items.append( dynamic_cast<QQuickItem*>(component.create()) );
m_items.back()->setParentItem(this);
m_items.back()->setProperty("y",100);

m_items.append( dynamic_cast<QQuickItem*>(component.create()) );
m_items.back()->setParentItem(this);
m_items.back()->setProperty("y",200);

}

void List::move(int x, int y)
{
foreach (QQuickItem* item, m_items) {
item->setProperty("x", item->x() + x);
item->setProperty("y", item->y() + y);
}
}

void List::keyPressEvent(QKeyEvent *event)
{
qDebug() << "keyPressed";
switch (event->key())
{
case Qt::Key_Up:
move(0,-50);
break;
case Qt::Key_Down:
move(0,50);
break;
}
}@

main.cpp
@#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"
#include "list.h"

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);

qmlRegisterType<List>("epg.list", 1, 0, "List");

QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile&#40;QStringLiteral("qml/epg/main.qml"&#41;&#41;;
viewer.showExpanded();

return app.exec&#40;&#41;;

}@

main.qml
@import QtQuick 2.0
import epg.list 1.0

Rectangle {
width: 360
height: 360
color:"blue"

List{
    anchors.fill: parent
    focus:true
}

}@

Cell.qml
@import QtQuick 2.0

Rectangle {
width: 100
height: 50

color: "green"

Behavior on y { NumberAnimation{duration: 400}}

onYChanged: {
    console.log("y changed")
}

onXChanged: {
    console.log("x changed")
}

}@

Yrchgrchh

I solved it by adding initial value m_items.back()->setProperty("y",0); for the first element of my list.
Not sure what type of magic is that but it works just fine now