QT: How to loop a method every second? C++

Question

I've created a Qt project which displays a circle on a widget. Then I have a method which redraws the circle at different positions every time I call the method. What I want is to run that method in a for loop, say ten times, and be shown each of the 10 positions that the circle is redrawn in every one second.

Something along the lines of:

void method::paintEvent(QPaintEvent * p)
{

//code

    for(int i=0; i<10;i++)//do this every second
    {
       method(circle[i]); //co-ordinates change
       circle[i].pain( & painter); //using QPainter
    }

//code

}

I've read about QTimer, but do not know how to use it. And the sleep function does not work.

Answer 1

All you need to do is to trigger an update() from the timer event. The update() method schedules a paintEvent on the widget.

It is invalid to paint on a widget outside of the paintEvent - that's the mistake that all other answers did at the time I posted this answer. Merely calling the paintEvent method is not a workaround. You should call update(). Calling repaint() would also work, but do so only when you have understood the difference from update() and have a very good reason for doing so.

class Circle;

class MyWidget : public QWidget {
  Q_OBJECT
  QBasicTimer m_timer;
  QList<Circle> m_circles;
  void method(Circle &);
  void paintEvent(QPaintEvent * p) {
    QPainter painter(this);
    // WARNING: this method can be called at any time
    // If you're basing animations on passage of time,
    // use a QElapsedTimer to find out how much time has
    // passed since the last repaint, and advance the animation
    // based on that.
    ...
    for(int i=0; i<10;i++)
    {
       method(m_circles[i]); //co-ordinates change
       m_circles[i].paint(&painter);
    }
    ...
  }
  void timerEvent(QTimerEvent * ev) {
    if (ev->timerId() != m_timer.timerId()) {
      QWidget::timerEvent(ev);
      return;
    }
    update();
  }
public:
  MyWidget(QWidget*parent = 0) : QWidget(parent) {
    ...
    m_timer.start(1000, this);
  }
};