Adding widgets to QScrollArea

[ser_bur]

Hi, guys.
Need some help...
The task is following: I need to place into QGroupBox some number of widgets - for example, QLabel. After filling this QGroupBox scrollbar must appear.
Code is next:

extGroupLayout = new QVBoxLayout;
groupBoxLayout = new QVBoxLayout;
scrollArea = new QScrollArea(this);
 
groupBox->setLayout(extGroupLayout);
extGroupLayout->addWidget(scrollArea);
scrollArea->setLayout(groupBoxLayout);
 
for(i=0;i<20;i++)
  {
//      Let's make our checkboxes...
     IDCheckbox[i] = new QCheckBox;
     groupBoxLayout->addWidget(IDCheckbox[i]);
  }

extGroupLayout = new QVBoxLayout;
groupBoxLayout = new QVBoxLayout;
scrollArea = new QScrollArea(this);

groupBox->setLayout(extGroupLayout);
extGroupLayout->addWidget(scrollArea);
scrollArea->setLayout(groupBoxLayout);

for(i=0;i<20;i++)
  {
//      Let's make our checkboxes...
     IDCheckbox[i] = new QCheckBox;
     groupBoxLayout->addWidget(IDCheckbox[i]);
  }

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After executing, checkboxes get minimal possible height, ignoring value, set by setMinimalHeight method; last of them are hiding behind the edge of scroll area, but scrolling is still impossible

Where is my problem? Don't say it is in my head