CODEWITHSUNDEEP
c++qtqt4repaintqgraphicsitem
onurozcelik
onurozcelik

Reputation: 1214

QGraphicsItem repaint

I want to change text color inside a rectangle periodically. Here is my trial:

 TrainIdBox::TrainIdBox()
 {
   boxRect = QRectF(0,0,40,15);
   testPen = QPen(Qt:red);
   i=0;
   startTimer(500);
 }

QRectF TrainIdBox::boundingRect() const
{
 return boxRect;
}

void TrainIdBox::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,   QWidget *widget)
{
  Q_UNUSED(widget);
  Q_UNUSED(option);

  painter->setPen(QPen(drawingColor,2));
  painter->drawRect(boxRect);
  painter->setPen(testPen);
  painter->drawText(boxRect,Qt::AlignCenter,"TEST");

 }
 void TrainIdBox::timerEvent(QTimerEvent *te)
 {
  testPen = i % 2 == 0 ? QPen(Qt::green) : QPen(Qt::yellow);
  i++;
  update(boxRect);
 }

This code does not working properly. What is wrong?

Upvotes: 3

Views: 7367

Answers (4)

grefab
grefab

Reputation: 2045

QGraphicsItem is not derived from QObject and hence does not have an event queue, which is needed to handle timer events. Try using QGraphicsObject or multiple inheritance of QGraphicsItem and QObject (which is exactly what QGraphicsObject does).

Upvotes: 3

Robert
Robert

Reputation: 10943

If you inherit from QGraphicsObject ... I give here an example:

Declare:

 class Text : public QGraphicsObject
    {
        Q_OBJECT

    public:
        Text(QGraphicsItem * parent = 0);
        void paint ( QPainter * painter,
                     const QStyleOptionGraphicsItem * option, QWidget * widget  );
        QRectF boundingRect() const ;
        void timerEvent ( QTimerEvent * event );

    protected:
        QGraphicsTextItem * item;
        int time;
    };

implementation:

Text::Text(QGraphicsItem * parent)
    :QGraphicsObject(parent)
{
    item = new QGraphicsTextItem(this);
    item->setPlainText("hello world");

    setFlag(QGraphicsItem::ItemIsFocusable);    
    time  = 1000;
    startTimer(time);
}

void Text::paint ( QPainter * painter,
                   const QStyleOptionGraphicsItem * option, QWidget * widget  )
{
    item->paint(painter,option,widget);    
}

QRectF Text::boundingRect() const
{
    return item->boundingRect();
}

void Text::timerEvent ( QTimerEvent * event )
{
    QString timepass = "Time :" + QString::number(time / 1000) + " seconds";
    time = time + 1000;
    qDebug() <<  timepass;
}

good luck

Upvotes: 2

mosg
mosg

Reputation: 12381

As the base point, you could watch Wiggly Example and find some errors in you code yourself, what is much better. For Qt, in my opinion, it's a good practice to look sometimes in Examples and Demos application.

Good luck!

Upvotes: 0

firescreamer
firescreamer

Reputation: 620

Check if Timer was properly initialized, it shouldn't return 0.

Try also changing color of brush used to paint.

I check your code when I get some free time in home, but that won't be before Sunday.

Upvotes: 0

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