QGridLayout *layout = new QGridLayout;
layout->addWidget(mytableview,0,0,1,3);
layout->addWidget(b1,1,0,1,1,Qt::AlignRight);
layout->addWidget(b2,1,1,1,1,Qt::AlignRight);
layout->addWidget(b3,1,2,1,1);
mainWindow->setLayout(layout);