signals:    void SendforeColor(const QChar &);
void PaintArea::SendforeColor(QColor &color){    color=QColor(foreColor);}
 
void MainWindow::recieveforeColor(const QColor  &color){    foreColor=QColor(color);    QPixmap pix=QPixmap(80,80);    pix.fill(foreColor);    ui->toolButton_3->setIcon(QIcon(pix));} connect(area,SIGNAL(SendforeColor(QColor &)),this,SLOT(recieveforeColor(QColor &)));能这样写不