Hello all!

I am trying to resize a QGraphicsItem when I resize the app window but its not working.
How could I do that?
Qt Code: 
  1. //Tool Box 3
  2.     QGridLayout *gridLayoutInvestimento5 = new QGridLayout(boxInvestimento3);
  3.     QGraphicsView *graphicsViewFluxoCaixa = new QGraphicsView(boxInvestimento3);
  4.     QGraphicsScene *graphicsSceneFluxoCaixa = new QGraphicsScene(graphicsViewFluxoCaixa);
  5.     graphicsViewFluxoCaixa->setScene(graphicsSceneFluxoCaixa);
  6.  
  7.     boxInvestimento3->setLayout(gridLayoutInvestimento5);
  8.     gridLayoutInvestimento5->addWidget(graphicsViewFluxoCaixa);
  9.  
  10.     //graphicsViewFluxoCaixa->adjustSize();
  11.  
  12.     //graphicsViewFluxoCaixa->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
  13.  
  14.     //graphicsViewFluxoCaixa->fitInView(graphicsSceneFluxoCaixa->itemsBoundingRect(), Qt::IgnoreAspectRatio);
  15.  
  16.     QPen caneta(Qt::black);
  17.     caneta.setWidth(4);
  18.     QGraphicsLineItem *linhaTempo = new QGraphicsLineItem(0,0,graphicsViewFluxoCaixa->width(),0);
  19.  
  20.     linhaTempo->setPen(caneta);
  21.     graphicsSceneFluxoCaixa->addItem(linhaTempo);
  22.     graphicsViewFluxoCaixa->adjustSize();
  23.     graphicsViewFluxoCaixa->setBackgroundBrush(QBrush(Qt::red));
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Thanks a lot.