QGraphicsView doesn't always update

Question

Hi I've got a GridLayout which has 64 GraphicsViews on it (I know it's alot but it's the only way i could think of doing this at this point in time). Now i'm currently just drawing a random line on each of these graphics views on a timer tick. This works but only for the 8 of the Graphics, Create Graphics Views
void Simulation::createGraphicsViews(){ for(int i = 0; i < 64; i++){ for(int j = 0; j < 8; j++){

        graphicsScene[i] = new QGraphicsScene();
        graphicsView[i] = new QGraphicsView(graphicsScene[i]);
        simui->gridLayout->addWidget(graphicsView[i], i/8, j);
        }

    }
}

Random Line in each graphics view

for(int x = 0; x < 64; x++){
    x1 = qrand()%(50+1) - 1;
    y1 = qrand()%(50+1)-1;
    x2 = qrand()%(50+1)-1;
    y2 = qrand()%(50+1)-1;
    graphicsScene[x]->addLine(x1,y1,x2,y2);
    qDebug() << "adding line to" << x << "at" << x1 <<","<<y1<<","<<x2<<","<<y2;
}

show updated graphics view

 for(int x = 0; x < 64; x++){
        graphicsView[x]->show();
        qDebug()<<"showing" << x;
  }

I've looked through it for the last 2 hours trying multiple approaches none of which have fixed this problem, I'm assuming it's probably something stupid but I just can't figure it out

Any help is greatly appreciated Thank you

Also if i try to update any of the Graphics Views other than the ones which work they still don't update.

https://gist.github.com/gazza126/f43d5b0377649782a35d -- Full Code (that does anything)

Answer 1

The below works. Make sure that you enable C++11 in your .pro file: add CONFIG += c++11 to the project file.

#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsLineItem>
#include <QGridLayout>
#include <QTime>
#include <QTimer>
#include <array>

class View : public QGraphicsView
{
public:
   View(QWidget *parent = 0) : QGraphicsView(parent) {
      setRenderHint(QPainter::Antialiasing);
   }
   void resizeEvent(QResizeEvent *) {
      fitInView(-1, -1, 2, 2, Qt::KeepAspectRatio);
   }
};

template <typename Container>
void updateScenes(Container & views)
{
   auto angle = 360.0/1000.0 * (QTime::currentTime().msecsSinceStartOfDay() % 1000);
   for (auto & view : views) {
      auto scene = view.scene();
      scene->clear();
      auto * line = scene->addLine(-1, 0, 1, 0, QPen(Qt::darkBlue, 0.1));
      line->setRotation(angle);
   }
}

int main(int argc, char *argv[])
{
   QApplication a(argc, argv);
   QGraphicsScene s;
   QTimer timer;
   QWidget window;
   QGridLayout layout(&window);
   std::array<View, 64> views;

   int i = 0;
   for (auto & view : views) {
      view.setScene(new QGraphicsScene(&view));
      layout.addWidget(&view, i/8, i%8);
      ++ i;
   }

   QObject::connect(&timer, &QTimer::timeout, [&views]{ updateScenes(views); });
   timer.start(50);
   window.show();
   return a.exec();
}