QPainter的不活跃

Question

下面的代码导致一堆错误：

void MainWindow::displayBoard() 
{ 
    QPixmap pix(0,0); 
    pix.fill(Qt::white); 
    QPainter painter(&pix); 
    painter.setBrush(Qt::black); 
    for(int row = 0; row < 8; row++) 
     for(int col = 0; col < 8; col++) 
      painter.drawRect(row * 10, col * 10, 10, 10); 
    ui->label->setPixmap(pix); 
} 

的错误：

QPainter::begin: Paint device returned engine == 0, type: 2 
QPainter::setBrush: Painter not active 
QPainter::drawRects: Painter not active 

我怎样才能解决这个问题？

Answer 1

问题是，科林指出，pix是零大小。