Problem in setting gridlayout.

Hi
i am setting a gridlayout in frame which is child class of MainWindow , but the widget which i set on layout are not gett display.Where i am wrong.My code is

Code:

NewWindow::NewWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::NewWindow)
{
   ui->setupUi(this);
   this->setStyleSheet("background-color:gray");
   QString string = "Home profile";
   w1 = new MainWindow(string ,this);//Custom Buttons object
      QString string1 = "Emergency Help";
   w2 = new MainWindow(string1 ,this);//Custom Buttons object
   QFrame *centralFrame=new QFrame(this);
   centralFrame->setStyleSheet("background-color:blue");
    this->setCentralWidget(centralFrame);
    QGridLayout *layout= new QGridLayout(centralFrame);
    layout->addWidget( w1,0,0);
     layout->addWidget( w2,1,1);
   centralFrame->setLayout(layout);
  centralFrame->setGeometry(160,180,400,200);
}

]

Thanks
Waiting for your reply.