How to connect QTimer with QPaintEvent?

[Asus_G72GX]

Spitfire great thanks for you that you helped me with this!
Anyway I have discussed this problem with my lector he showed me that it possiblee to move ellipse if we declare a coordinates for it like a dx ,dy,x,y.
The final result must be close to this images below:



But I have collided that Qt does not see a z coordinate. So I make them by x,y. My code result is close to those sample images, but I was not able to move the ball to the right and upwards. Maybe is it possible to change the values? Thanks again!
Widget.h

#ifndef WIDGET_H
#define WIDGET_H
 
#include <QtGui>
 
class Widget : public QWidget
{
Q_OBJECT
 
public:
Widget(QWidget *parent = 0);
~Widget();
 
QGridLayout *grid;
//QWidget *widget1;
QPen *pen;
QBrush *brush, *brush1;
//QTimer *timer;
QMatrix matrix;
 
void paintEvent(QPaintEvent *);
int x;
int x2;
 
int y;
int y2;
int dx, dy;
int dx2, dy2;
 
void timerEvent(QTimerEvent *);
void timerEvent1(QTimerEvent *);
public slots:
void move();
};
 
#endif // WIDGET_H

#ifndef WIDGET_H
#define WIDGET_H

#include <QtGui>

class Widget : public QWidget
{
Q_OBJECT

public:
Widget(QWidget *parent = 0);
~Widget();

QGridLayout *grid;
//QWidget *widget1;
QPen *pen;
QBrush *brush, *brush1;
//QTimer *timer;
QMatrix matrix;

void paintEvent(QPaintEvent *);
int x;
int x2;

int y;
int y2;
int dx, dy;
int dx2, dy2;

void timerEvent(QTimerEvent *);
void timerEvent1(QTimerEvent *);
public slots:
void move();
};

#endif // WIDGET_H

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Main.cpp

#include <QtGui/QApplication>
#include "widget.h"
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
 
    return a.exec();
}

#include <QtGui/QApplication>
#include "widget.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();

    return a.exec();
}

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Widget.cpp

#include "widget.h"
 
 
Widget::Widget(QWidget *parent)
: QWidget(parent)
{
grid = new QGridLayout;
 
QPainter painter(this);
 
//widget1= new QWidget;
//grid->addWidget(widget1,0,6,0,6);
this->setLayout(grid);
 
pen = new QPen;
brush = new QBrush;
 
//pen->setColor(Qt::blue);
brush->setColor(Qt::red);
//timer = new QTimer(this);
/*x =  10;
 
dx = 5;
dy = 10;
y =30;*/
 
 
x =  10;
dx = 5;
dy = 10;
y =30;
 
 
x2 =  10;
dx2 = 5;
dy2 = 10;
y2 =30;
 
 
 
 
 
 
 
 
 
//connect(timer, SIGNAL(timeout()), this,SLOT(move()));
//timer->start(3000);
this->startTimer(100);
 
}
 
void Widget::timerEvent(QTimerEvent *){
 
    x = x + dx;
 
 
    if(x >=165) dx = -5;
    if(x  <0) dx = 5;
 
 
    y = y + dy;
 
 
    if(y <=-165) dy = 10;
    if(y  >0) dy = -10;
 
 
 
 
 
 
 
// 2nd leg for blue ball
 
 
    x2 = x2+ dx2;
 
 
    if(x2 >=165) dx2 = 5;
    if(x2  <0) dx2 = -5;
    if(x2>5) dx2=1;
 
 
    y2 = y2- dy2;
 
 
    if(y2 <=-165) dy2 = 10;
    if(y2  >0) dy2 = -10;
    if(y2>-10) dx2=15;
    /*if(y2>=100) dy2=5;
    if(y2>0) dy2=-5;*/
 
   /* y2 = y2 + dy2;
 
        if(y2 <=100) dy2 = 1;
        if(y2  >0) dy2 = -1;*/
 
 
    update();
}
 
 
Widget::~Widget()
{
 
}
void Widget::paintEvent(QPaintEvent *)
{
    QPainter painter (this);
    painter.setBrush(Qt::red);
 
 
/*QRadialGradient radialGradient(50, 50, 50, 70, 70);
  radialGradient.setColorAt(0.0, Qt::white);
  radialGradient.setColorAt(0.2, Qt::green);
  radialGradient.setColorAt(1.0, Qt::black);
  painter.setBrush(radialGradient);*/
  painter.drawEllipse(x,y,40,40);
  painter.setBrush(Qt::blue);
  painter.drawEllipse(x2,y2,10,10);
 
}
void Widget::move()
 
{
    QPainter painter (this);
    painter.drawEllipse(0,0,165,165);
}

#include "widget.h"


Widget::Widget(QWidget *parent)
: QWidget(parent)
{
grid = new QGridLayout;

QPainter painter(this);

//widget1= new QWidget;
//grid->addWidget(widget1,0,6,0,6);
this->setLayout(grid);

pen = new QPen;
brush = new QBrush;

//pen->setColor(Qt::blue);
brush->setColor(Qt::red);
//timer = new QTimer(this);
/*x =  10;

dx = 5;
dy = 10;
y =30;*/


x =  10;
dx = 5;
dy = 10;
y =30;


x2 =  10;
dx2 = 5;
dy2 = 10;
y2 =30;









//connect(timer, SIGNAL(timeout()), this,SLOT(move()));
//timer->start(3000);
this->startTimer(100);

}

void Widget::timerEvent(QTimerEvent *){

    x = x + dx;


    if(x >=165) dx = -5;
    if(x  <0) dx = 5;


    y = y + dy;


    if(y <=-165) dy = 10;
    if(y  >0) dy = -10;







// 2nd leg for blue ball


    x2 = x2+ dx2;


    if(x2 >=165) dx2 = 5;
    if(x2  <0) dx2 = -5;
    if(x2>5) dx2=1;


    y2 = y2- dy2;


    if(y2 <=-165) dy2 = 10;
    if(y2  >0) dy2 = -10;
    if(y2>-10) dx2=15;
    /*if(y2>=100) dy2=5;
    if(y2>0) dy2=-5;*/

   /* y2 = y2 + dy2;

        if(y2 <=100) dy2 = 1;
        if(y2  >0) dy2 = -1;*/


    update();
}


Widget::~Widget()
{

}
void Widget::paintEvent(QPaintEvent *)
{
    QPainter painter (this);
    painter.setBrush(Qt::red);


/*QRadialGradient radialGradient(50, 50, 50, 70, 70);
  radialGradient.setColorAt(0.0, Qt::white);
  radialGradient.setColorAt(0.2, Qt::green);
  radialGradient.setColorAt(1.0, Qt::black);
  painter.setBrush(radialGradient);*/
  painter.drawEllipse(x,y,40,40);
  painter.setBrush(Qt::blue);
  painter.drawEllipse(x2,y2,10,10);

}
void Widget::move()

{
    QPainter painter (this);
    painter.drawEllipse(0,0,165,165);
}

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[Spitfire]

You should be using OO approach.

Create a class 'ball', give it what you need and then move it around.
Parent widget can be canvas for the ball to move around.

To move ball in oposite direction, just multiply dx and/or dy by -1 every time you hit some edge.

here's example ball class:

class Ball : public QWidget
{
    Q_OBJECT
public:
    Ball( int dx, int dy, QWidget* parent = 0 )
        :
        QWidget( parent ),
        dx( dx ),
        dy( dy )
    {
        this->setFixedSize( 20, 20 );
    }
 
public slots:
    void    advance( void )
    {
        QPoint p = this->pos();
 
        int x = p.x() + this->dx;
        if( x < 0 )
        {
            x = 0;
            this->dx *= -1;
        }
        else if( x + this->width() > this->parentWidget()->width() )
        {
            x = this->parentWidget()->width() - this->width();
            this->dx *= -1;
        }
 
        int y = p.y() + this->dy;
        if( y < 0 )
        {
            y = 0;
            this->dy *= -1;
        }
        else if( y + this->height() > this->parentWidget()->height() )
        {
            y = this->parentWidget()->height() - this->height();
            this->dy *= -1;
        }
 
        this->move( x, y );
    }
 
protected:
    void    paintEvent( QPaintEvent* e )
    {
        Q_UNUSED( e );
 
        QPainter p( this );
        QPainterPath pp;
        pp.addEllipse( this->rect() );
        p.fillPath( pp, Qt::red );
    }
 
private:
    int     dx;
    int     dy;
};

class Ball : public QWidget
{
    Q_OBJECT
public:
    Ball( int dx, int dy, QWidget* parent = 0 )
        :
        QWidget( parent ),
        dx( dx ),
        dy( dy )
    {
        this->setFixedSize( 20, 20 );
    }

public slots:
    void    advance( void )
    {
        QPoint p = this->pos();

        int x = p.x() + this->dx;
        if( x < 0 )
        {
            x = 0;
            this->dx *= -1;
        }
        else if( x + this->width() > this->parentWidget()->width() )
        {
            x = this->parentWidget()->width() - this->width();
            this->dx *= -1;
        }

        int y = p.y() + this->dy;
        if( y < 0 )
        {
            y = 0;
            this->dy *= -1;
        }
        else if( y + this->height() > this->parentWidget()->height() )
        {
            y = this->parentWidget()->height() - this->height();
            this->dy *= -1;
        }

        this->move( x, y );
    }

protected:
    void    paintEvent( QPaintEvent* e )
    {
        Q_UNUSED( e );

        QPainter p( this );
        QPainterPath pp;
        pp.addEllipse( this->rect() );
        p.fillPath( pp, Qt::red );
    }

private:
    int     dx;
    int     dy;
};

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