layout in widget give me an empty window!

[rimie23]

when i change this line

mVerticalLayout-> addWidget(central);

mVerticalLayout-> addWidget(central);

To copy to clipboard, switch view to plain text mode 

by this

central->setLayout(mVerticalLayout);

central->setLayout(mVerticalLayout);

To copy to clipboard, switch view to plain text mode 

i see an empty window (there no groupbox, no scene)