Custom QGraphicsItem paint function problem

[andzero]

Hello!

I have a class that inherits QGraphicsItem and QObject:

class Foo: public QObject, public QGraphicsItem
{
   Q_OBJECT
   ...
};

class Foo: public QObject, public QGraphicsItem
{
   Q_OBJECT
   ...
};

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I have set up a QTimer, and connects its timeout signal with QGraphicsScene's advance.

I want to display 2 constantly shifting QPixmap on a Foo instance when it is shown:

void Foo::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawPixmap(bodyRect, animate?pic1:pic2); // animate is a boolean variable.
    if(animate) animate = false;
    else animate = true;
}

void Foo::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawPixmap(bodyRect, animate?pic1:pic2); // animate is a boolean variable.
    if(animate) animate = false;
    else animate = true;
}

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e.g., imagine a character walking animation with left foot pixmap and right foot pixmap.

My problem is, the result shown is not as what i have expected.
it looks like pic1 is drawn above pic2 or vice versa.
( pic1 and pic2 is a .png file, supports transparent background. does that have any effect :? )

is it impossible to make this, via paint function re-implementation?
(i'm doing this for learning purposes)

Thanks for your help and attention!

[stampede]

The pixmap will be switched each time the paint method is called, this is probably not what you want.
Connect the timer to a slot, where you will switch the pixmap and update the item:

/*slot*/
void Foo::timeout(){
    if( this->_pixmap == pixmap1 ){
        this->_pixmap = pixmap2;
    } else{
        this->_pixmap = pixmap1;
    }
    update();
}
 
void Foo::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawPixmap(bodyRect, this->_pixmap);
}

/*slot*/
void Foo::timeout(){
    if( this->_pixmap == pixmap1 ){
        this->_pixmap = pixmap2;
    } else{
        this->_pixmap = pixmap1;
    }
    update();
}

void Foo::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->drawPixmap(bodyRect, this->_pixmap);
}

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Now on each timeout the pixmap will be switched, and item updated, no matter how often its rendered.
Btw. If you are using Qt >= 4.6, take a look at the QGraphicsObject class.