Scroll area and its child widget

Hi everyone,
I have a widget with grid layout. The 1st row of grid layout contains another widget. For fullscreen mode stretching is happening for the child widget.

Now I am trying to add another widget at 2nd row and a scroll for 1st widget. So instead of adding widget directly to 1st row I am using a QScrollArea.

MainWidget -> grid layout -> scroll area(1st row) -> 1st widget

It is working fine. Scroll bar is coming for 1st widget.
But problem is for full screen the widget is not stretching like 1st case (like layout).
I tried setWidgetResizable(true). Streatching is fine but scroll bar is not coming.

Can anybody tell me a way so that the widget will fit to scroll area and and scroll bar will appear when it is required ?

thanks.