Error on creating QPropertyAnimation object

behruz montazeri

Header file :

#ifndef MYRECT_H
#define MYRECT_H
#include <QGraphicsItem>
#include <QPropertyAnimation>

class MyRect:public QGraphicsItem
{
    Q_PROPERTY(QRect nrect READ nRect WRITE setNrect)

public:
    MyRect();
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
    QRectF boundingRect() const;
    QRect nRect()const;
    void setNrect(const QRect &rect);
protected:
private:
    QRect mRect;
    QPropertyAnimation *anime;

};

#endif // MYRECT_H

In cpp file :

    anime = new QPropertyAnimation(this,"nrect");   //error
    anime->setDuration(2000);
    anime->setStartValue(QRect(0,0,10,10));
    anime->setEndValue(QRect(0,0,50,50));
    anime->start();

    QObject::connect(anime,&QPropertyAnimation::valueChanged,[=](){update();});

sierdzio

QGraphicsItem is not a QObject. It cannot have Qt properties.

So, either use multiple inheritance to inherit from QGraphicsItem and QObject, or use Q_GADGET macro (and don't pass any parent to QPropertyAnimation).

behruz montazeri

@sierdzio
Thanks.How should i create QPropertyAnimation object ?

behruz montazeri

class MyRect:public QGraphicsItem,public QObject
{
    Q_PROPERTY(QRect nrect READ nRect WRITE setNrect)

It seems QPropertyAnimation doen't know nrect
QPropertyAnimation: you're trying to animate a non-existing property nrect of your QObject

sierdzio

Do you have Q_OBJECT macro in your header file?

behruz montazeri

@sierdzio
If i add Q_OBJECT it generates errors.
I made a new class from QObject and it solves the problem.

sierdzio

@behruz-montazeri said in Error on creating QPropertyAnimation object:

@sierdzio
If i add Q_OBJECT it generates errors.

What errors? You need to fix them.

There is no way a QObject with properties will work without the macro, you have to have it.

behruz montazeri

@sierdzio
Also instead of QGraphicsItem We can use QGraphicsObject