how to access layout within another layout in qt

I got an error when running my qt program. (It used to work and can be compiled perfectly before I add this new function void perfectPanel::aaaf in order to do something.) The error message is,

Quote:

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QLayout::parentWidget: A layout can only have another layout as a parent. Segmentation fault (core dumped)

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It happens since I was trying to add a new widget to my layout gridLayoutSub_, but layout gridLayoutSub_ is within another layout, let's call it gridLayout_

Code:

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void perfectPanel::aaaf()
{
    // some codes ...
    gridLayoutSub_->addWidget(kkk, 6, 0, 1, 1);
}

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Anyone knows what's going wrong and how to fix it?

More details: Declarations of these two layouts

In mymainwindow class, there is a dock widget. And in order to customize this dock widget, I wrote a new class called perfectPanel which is a subclass of QWidget, and then in the constructor of this perfectPanel, I have the following codes:

Code:

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groupBoxA = new QGroupBox(tr("groupBoxA"));
QGridLayout* gridLayoutA = new QGridLayout(groupBoxA);
 
VBoxLayoutPanel = new QVBoxLayout(this);
VBoxLayoutPanel->addWidget(groupBoxA);
 
groupBoxA->setLayout(gridLayoutA);
setLayout(VBoxLayoutPanel);

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As you can see, gridLayoutA is within another layout VBoxLayoutPanel. And the error I mentioned happens when I try to addWidget to gridLayoutA later in function void perfectPanel::aaaf, during:

Code:

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gridLayoutA->addWidget(kkk, 6, 0, 1, 1);

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The header of perfectPanel class

Code:

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class perfectPanel : public QWidget
{
    Q_OBJECT
 
public:
 
    explicit perfectPanel(QWidget *parent = 0);
    ~perfectPanel();
 
private:
    // ...
}

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Everything looks fine, it should just work. I think there somthing else you are doing, which missed to mention.

I found if I VBoxLayoutPanel.addWidget(), this works. So I am wondering what's the reason that i can only addWidget to parent layout not sub-layout?

Can you reproduce the warning with a sample project?