QGraphicsScene、QGraphicsView和QVBoxLayout()问题

Question

大家好，

每次我运行Qt时，当我注释掉行//mainWindow = new MainWindow();时，似乎Qt就停止工作了，但是如果不注释掉行，, MainWindow就会多次出现。另外，检查QGraphicsScene、QGraphicsView和QVBoxLayout的结构是否正确，因为在main.cpp中调用MainWindow时，我似乎无法使视图出现。

谢谢:)

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent), keydown_left(false), keydown_right(false),scene(NULL), view(NULL)
{
    qDebug("MainWindow");
    //mainWindow = new MainWindow();
    //qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));
    scene = new QGraphicsScene(mainWindow);
    view = new QGraphicsView(scene, mainWindow);

    scene->setSceneRect(-300, 0, 640, 360);
    scene->setItemIndexMethod(QGraphicsScene::NoIndex);
    Egg *egg = new Egg();

    QVBoxLayout *layout = new QVBoxLayout();

    for (int i = 0; i < ObjCount; ++i) {
        FlyingObj *Fo= new FlyingObj();
        Fo->setPos(::sin((i * 6.28) / ObjCount) * 500,
                   ::cos((i * 6.28) / ObjCount) * 500);
        scene->addItem(Fo);
    }
    egg->setPos((640-64)/2, 100);//16 - 2*16
    scene->addItem(egg);


    view->setRenderHint(QPainter::Antialiasing);
    view->setBackgroundBrush(QPixmap(":/bg.jpg"));
    //view->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
    view->setDragMode(QGraphicsView::NoDrag);
    view->setWindowTitle(QT_TRANSLATE_NOOP(QGraphicsView, "Egg game"));
    view->resize(640, 360);
    QObject::connect(scene, SIGNAL(keyPressEvent(QKeyEvent)), this, SLOT(keyPressEvent(QKeyEvent)));
    view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view->setFrameStyle(QFrame::NoFrame);
    view->setFocusPolicy(Qt::NoFocus);
    view->setCacheMode(QGraphicsView::CacheBackground);
    view->showFullScreen();

    layout->addWidget(view);
    QWidget *w = new QWidget();
    w->setLayout(layout);
}

Answer 1

尝试在项目中包含main函数，通常在文件: Main.cpp中单独定义，其中实例化您的MainWindow类：

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();
    return a.exec();
}

在mainWindow构造函数中取消注释MainWindow是一个递归调用，并且在这个上下文中是不正确的。最后，努力改变：

    layout->addWidget(view);
    QWidget *w = new QWidget();
    w->setLayout(layout);

转入：

   setLayout(layout);