Stuck with QGraphicsItem's setPos() method

[salmanmanekia]

// HEADER FILE

class exclass :public QObject, public QGraphicsItem
{
    Q_OBJECT
 
public:
	exclass(QGraphicsItem *parent = 0);
       QRectF boundingRect() const;
	void paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget);
private:
	Ui::exclassClass ui;
};
 
class playButtonLayout : public exclass
{
private:
	QWidget *widg; 
	QString str;
 
	QPushButton *stopButton;
	QPushButton *playButton;	
	QHBoxLayout *hboxLay;
 
public:
	playButtonLayout();
	QRectF boundingRect() const;
	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
};

class exclass :public QObject, public QGraphicsItem
{
    Q_OBJECT

public:
	exclass(QGraphicsItem *parent = 0);
       QRectF boundingRect() const;
	void paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget);
private:
	Ui::exclassClass ui;
};

class playButtonLayout : public exclass
{
private:
	QWidget *widg; 
	QString str;
	
	QPushButton *stopButton;
	QPushButton *playButton;	
	QHBoxLayout *hboxLay;
	
public:
	playButtonLayout();
	QRectF boundingRect() const;
	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
};

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// MAIN METHOD

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QGraphicsScene scene(-200,-200,400,400);
    exclass *mainScene = new exclass;
 
    mainScene->setPos(1.2,1.2);
    scene.addItem(mainScene);
    QGraphicsView view(&scene);
 
    view.show();
    return a.exec();
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QGraphicsScene scene(-200,-200,400,400);
    exclass *mainScene = new exclass;
  
    mainScene->setPos(1.2,1.2);
    scene.addItem(mainScene);
    QGraphicsView view(&scene);
        
    view.show();
    return a.exec();
}

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// SOURCE FILE

#include "exclass.h"
 
exclass::exclass(QGraphicsItem *parent): QGraphicsItem(parent)
{
	playButtonLayout *playLayoutItem = new playButtonLayout(); 
	playLayoutItem->setPos(0,20);
}
 
 
 
QRectF exclass::boundingRect() const 
{
 
}
 
void exclass::paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget)
{
 
}
 
playButtonLayout::playButtonLayout()
{
	hboxLay = new QHBoxLayout;
	playButton = new QPushButton;
	stopButton = new QPushButton;
	widg = new QWidget;
	playButton->setIcon(QIcon("./images/play.JPG"));
	stopButton->setIcon(QIcon("./images/stop.JPG"));
	hboxLay->addWidget(playButton);
	hboxLay->addWidget(stopButton);
	widg->setLayout(hboxLay);
	str = "salman" ;	
}
 
QRectF playButtonLayout::boundingRect() const 
{
 
}
 
void playButtonLayout::paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget)
{}

#include "exclass.h"

exclass::exclass(QGraphicsItem *parent): QGraphicsItem(parent)
{
	playButtonLayout *playLayoutItem = new playButtonLayout(); 
	playLayoutItem->setPos(0,20);
}

 

QRectF exclass::boundingRect() const 
{
	
}

void exclass::paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget)
{
	
}

playButtonLayout::playButtonLayout()
{
	hboxLay = new QHBoxLayout;
	playButton = new QPushButton;
	stopButton = new QPushButton;
	widg = new QWidget;
	playButton->setIcon(QIcon("./images/play.JPG"));
	stopButton->setIcon(QIcon("./images/stop.JPG"));
	hboxLay->addWidget(playButton);
	hboxLay->addWidget(stopButton);
	widg->setLayout(hboxLay);
	str = "salman" ;	
}

QRectF playButtonLayout::boundingRect() const 
{
	
}

void playButtonLayout::paint(QPainter *painter,const QStyleOptionGraphicsItem *option,QWidget *widget)
{}

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I have written this code,i know that some of these things even dont make sense ,but i was trying many things and i also tried this way .....Help would be appreciated