Application with two MainWindows (switchable)

[Santosh Reddy]

1). But I had to set the window flag of the Mainwindows to host as a central widget to Qt::Widget (using QMainWindow::setWindowFalg)

That should not be required.

Even if I trie to hide them before.

No need to hide, just don't show them in the first place, just add to layout and only show the host QMainWindow (top level window)