Hi, everyone,

I have a CircleItem class which inherits QCanvasEllipse. I reimplement areaPoints() and drawShape(). When I'm trying to move CircleItem, it doesn't work.

Why? what else should I do?

Qt Code: 
  1. /////////////////////////////////////////////////////////////////////////
  2. class CircleItem : public QCanvasEllipse
  3. {
  4. public:
  5.     CircleItem( int cx, int cy, int r, QCanvas *c ) : QCanvasEllipse( c )
  6.     {
  7.         this->cx = cx;
  8.         this->cy = cy;
  9.         this->r  = r;
  10.     }
  11.  
  12.     ~CircleItem()
  13.     {
  14.         hide(); 
  15.     }
  16.  
  17.     QPointArray areaPoints() const
  18.     {
  19.         QPointArray res(4);
  20.         res.setPoint( 0, QPoint( cx-r, cy-r ) );
  21.         res.setPoint( 1, QPoint( cx-r, cy+r ) );
  22.         res.setPoint( 2, QPoint( cx+r, cy+r ) );
  23.         res.setPoint( 3, QPoint( cx+r, cy-r ) );
  24.         return res;
  25.     }
  26.  
  27.  
  28. protected:
  29.     void drawShape( QPainter &p )
  30.     {
  31.         p.drawEllipse( cx-r, cy-r, 2*r, 2*r );
  32.     }
  33.  
  34. private:
  35.     int cx;
  36.     int cy;
  37.     int r;
  38. };
  39.  
  40. /////////////////////////////////////////////////////////////////////////
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Here are two methods that draw a circle on MyCanvasView. The first one uses QCanvasEllipse, it works fine. The second uses my CircleItem, it doesn't work.

Qt Code: 
  1. void MyCanvasView::drawCircle-1()
  2. {
  3.     QPoint p0 = inverseWorldMatrix().map(points[0]);
  4.     QPoint p1 = inverseWorldMatrix().map(points[1]);
  5.  
  6.     int r = (int) sqrt( pow(p0.x()-p1.x(),2)+pow(p0.y()-p1.y(),2) );
  7.  
  8.     QCanvasPolygonalItem* i = new QCanvasEllipse(2*r, 2*r, canvas());;
  9.     i->move(p0.x(), p0.y());
  10.     i->setBrush( Qt::red );  ***********
  11.     i->show();
  12.  
  13. }
  14.  
  15.  
  16. void MyCanvasView::drawCircle-2()
  17. {
  18.     QPoint p0 = inverseWorldMatrix().map(points[0]);
  19.     QPoint p1 = inverseWorldMatrix().map(points[1]);
  20.  
  21.     int r = (int) sqrt( pow(p0.x()-p1.x(),2)+pow(p0.y()-p1.y(),2) );
  22.  
  23.    QCanvasPolygonalItem* i  = new CircleItem(p0.x(), p0.y(), r, canvas());;
  24.     i->setPen(ROIPEN);  ***********
  25.     i->show();
  26.  
  27. }
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The Doc says:
Note: QCanvasEllipse does not use the pen.
In my subclass, I used setPen(), because I need to draw the outline of the circle instead of filling it.

Maybe this is the cause?

Can anyone help?

Thanks!