Scroll Area problem

Hi, i have a problem with scroll area...

i need some widget with some components and put it all into scroll area. But when i write:

Code:

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ui->scrollarea->setWidget(QLabel);

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and QLabel size is bigger then scroll area, everything works.

when i write:

Code:

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ui->scrollarea->setWidget(QWidget);

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it does not work !.. i can not see scrool bar..

i try: Widget, frame, layout, ... but it works only with QLabel.