如何访问QGridLayout中的小部件坐标

我正在将qlabel放在QGridLayout中，以便在从QWidget派生的类中很好地排列它们。但是，当我尝试访问坐标时，它总是返回(0,0)

class brick : public QWidget
{
Q_OBJECT
public:
    explicit brick(QWidget *parent);
    ...
private:
    QLabel* label;
    QPixmap* brickPic;
}
brick::brick(QWidget *parent) :
QWidget(parent)
{
rect=new QRect();
label=new QLabel;
brickPic=new QPixmap(100,15);
brickPic->fill(QColor(255,0,0));
label->setPixmap(*brickPic);
}
class Grid : public QWidget
{    
QOBJECT
public:
    void fill_grid(QWidget* parent);
    ...
private:
    QGridLayout* grid;
}
void Grid::fill_grid(QWidget* parent)
{
for (int i=0;i<10;i++)
{
    for (int j=0;j<12;j++)
    {
        brick* fillingBrick=new brick(parent);
        grid->addWidget(fillingBrick->getLabel(),j,i);
        qDebug()<<fillingBrick->parentWidget();
        brickVector.push_back(fillingBrick);
    }
}
}

这些将像我之前所说的那样显示在以下从QWidget派生的类中:

class render_area : public QWidget
{
Q_OBJECT
public:
    render_area(QWidget *parent = 0);
    Grid* getGrid() const;
    ...
private:
    Grid* grid;
    QRect* bar;
    ...
}
render_area::render_area(QWidget *parent)
:QWidget(parent)
{
    setFocusPolicy(Qt::StrongFocus);
    setBackgroundRole(QPalette::Base);
    setAutoFillBackground(true);
    bar=new QRect(width()/2,height()+50,150,10);
    grid=new Grid(this);
    grid->fill_grid(this);
    std::cout<<"Grid filled !"<<std::endl;
    qDebug()<<grid->getBrick(5)->pos();
    ...
}

qDebug()<<fillingBrick->parentWidget()返回良好的render_area，而qDebug()<<grid->getBrick(5)->pos()返回不良的QPoint(0,0)。

我想知道如何让pos()或x()和y()返回render_area中的坐标，其中每个砖都放置在其中。我尝试了从QGridLayout的cellRect，从QWidget继承的MapToParent()，迫使render_area到show();，但到目前为止没有运气。

编辑:这就是我说的循环:

void render_area::update_timer()
{
int x1,x2,y1,y2;
bar->getCoords(&x1,&y1,&x2,&y2);
if(is_fixed==false)
{
    //gestion du sol
    if(yc+diametre>height())
    {
        timer.stop();
        QDialog* gameOver=new QDialog;
        gameOver->setLayout(new QGridLayout);
        gameOver->layout()->addWidget(new QPushButton("Ok"));
        gameOver->setGeometry(500,500,300,150);
        gameOver->show();
    }
    if(xc>x1 && xc<x1+150)
    {
        if(yc+diametre>y1)
        {
            vyc=-vyc;
        }
    }
    //plafond
    for (int i=0;i<12;i++)
    {
        for(int j=0;j<10;j++)
        {
            grid->getBrick(i,j)->setRect(grid->getGrid()->cellRect(i,j));
        }
    }
    for(int i=0;i<widgets.size();i++)
    {
            if(widgets.at(i)->getRect()->intersects(ballRectangle))
            {
                std::cout<<i<<std::endl;
                widgets.at(i)->getPixmap()->fill(QColor(255,255,255));
                widgets.at(i)->getLabel()->setPixmap(*(widgets.at(i)->getPixmap()));
                delete widgets.at(i);
                vyc=-vyc;
            }
            //qDebug()<<grid->getBrick(i,j)->getRect();
    }
    //bord droit
    if(xc+diametre>width())
    {
            vxc=-vxc;
    }
    //bord gauche
    if(xc<0)
    {
            vxc=-vxc;
    }
    //integration (Euler explicite)
    xc=xc+dt*vxc;
    yc=yc+dt*vyc;
}
repaint();
}