find all group boxes in layout

thewiggin

Hello,
I am trying to find the layout attached to a group box, with a specific title, that is inside another layout so I can add a new label that group box's layout.

TestTab::TestTab(QWidget *parent) : QWidget(parent)
{
QVBoxLayout *mainLayout = new QVBoxLayout;    
QGroupBox *newGrpBox = new QGroupBox("VCM");
QVBoxLayout *grpLayout = new QVBoxLayout(newGrpBox);
QLabel *tstLbl = new QLabel("Hello");
grpLayout->addWidget(tstLbl);
newGrpBox->setLayout(grpLayout);
mainLayout->addWidget(newGrpBox);   
setLayout(mainLayout);

QList<QGroupBox*> childGrps = mainLayout->findChildren<QGroupBox*>();
foreach(auto obj, childGrps)
{
    qDebug() << "found group box";
    if(obj->title() == "VCM")
    {
        qDebug() << "Found box with VCM title";
        QList<QVBoxLayout*> grpLay = obj->findChildren<QVBoxLayout*>();
        foreach (auto layOjb, grpLay)
        {
            qDebug() << "Found grp box layout";
            QLabel *newLbl = new QLabel("new lbl");
            layOjb->addWidget(newLbl);
        }
    }
}
}

The qDebug statements do not appear from any level for the nested loops indicating that it finds no QGroupBoxes inside the mainLayout. Is there something wrong in my iteration loops? I can't declare the mainLayout to be the parent of the group box on declaration without a compiler error but I thought addWidget takes care of parenting issues and would make the group box a child of that layout. How should I go about accomplishing this task?

JoeCFD

set object name to each group box and use findChild<QGroupBox *> with object name to find any of them as Jon suggested. Layout is not needed.

JonB

@thewiggin
You can do this findChildren() stuff from widgets downward. You are trying to do it from layouts, and that's not how Qt works, parent-child-wise. See e.g. https://stackoverflow.com/questions/4065378/qt-get-children-from-layout

The layout does not "inject" itself in the parent-child tree, so the widgets stay (direct) children of their parent widget.

You could use QLayout::count() and QLayout::itemAt() instead.

Read the comments and answers there for explanation/suggestions.

thewiggin

Thank you.

I can find the layout inside the QGroupBox based off the link you provided:

    QVBoxLayout *vidGrpLay = newGrpBox->findChild<QVBoxLayout*>();
    if(vidGrpLay)
    {
        qDebug() << "Found grp box layout";
        QLabel *newVidGrpLbl = new QLabel("Vid property");
        vidGrpLay->addWidget(newVidGrpLbl);
    }

I am still having trouble understanding how to use count and itemAt to do what I want.

TestTab::TestTab(QWidget *parent) : QWidget(parent)
{
QVBoxLayout *mainLayout = new QVBoxLayout;    
QGroupBox *newGrpBox = new QGroupBox("VCM");
QVBoxLayout *grpLayout = new QVBoxLayout(newGrpBox);
QLabel *tstLbl = new QLabel("Hello");
grpLayout->addWidget(tstLbl);
newGrpBox->setLayout(grpLayout);
mainLayout->addWidget(newGrpBox);   
setLayout(mainLayout);
    QGroupBox *vidGrp;
    for(int i = 0; i < mainLayout->count(); ++i)
    {
        vidGrp = dynamic_cast<QGroupBox*>(mainLayout->itemAt(i));
        if(vidGrp)
        {
            qDebug() << "Found a group box";
            if(vidGrp->title() == "VCM")
            {
                qDebug() << "Found VCM group box";
                QVBoxLayout *vidGrpLay = vidGrp->findChild<QVBoxLayout*>();
                if(vidGrpLay)
                {
                    qDebug() << "Found VCM grp box layout";
                    QLabel *newVidGrpLbl = new QLabel("Vid property");
                    vidGrpLay->addWidget(newVidGrpLbl);
                }
                break;
            }
            else
            {
                vidGrp = nullptr;
            }
        }
    }
}

How do I check if the mainLayout->itemAt(i) is a QGroupBox?

JonB

@thewiggin said in find all group boxes in layout:

How do I check if the mainLayout->itemAt(i) is a QGroupBox?

QGroupBox *gb = qobject_cast<QGroupBox *>(mainLayout->itemAt(i));    // or dynamic_cast<>()
if (gb)
    qDebug() << "It's a QGroupBox!";

EDIT
Oh I just saw you have

        vidGrp = dynamic_cast<QGroupBox*>(mainLayout->itemAt(i));
        if(vidGrp)

so that should work?

JoeCFD

set object name to each group box and use findChild<QGroupBox *> with object name to find any of them as Jon suggested. Layout is not needed.

thewiggin

The dynamic cast returns nothing and the qobject_cast throws a compile error:
testtab.cpp:79: error: no matching function for call to ‘qobject_cast<QGroupBox*>(QLayoutItem*)’
79 | QGroupBox vidGrp = qobject_cast<QGroupBox>(mainLayout->itemAt(i));
| ^

QGroupBox *vidGrp = qobject_cast<QGroupBox*>(mainLayout->itemAt(i));

thewiggin

@JoeCFD Thanks using find child tied to object name worked

Not sure why the dynamic cast did not return it or why qobject_cast throws an error but the below snippet works when combined with the other code that has been posted.

    newGrpBox->setObjectName("vidGrpBox");
    QGroupBox *findGp = findChild<QGroupBox*>("vidGrpBox");
    if(findGp)
    {
        QVBoxLayout *vidGrpLay = findGp->findChild<QVBoxLayout*>();
        if(vidGrpLay)
        {
            qDebug() << "Found grp box layout";
            QLabel *newVidGrpLbl = new QLabel("Vid property");
            vidGrpLay->addWidget(newVidGrpLbl);
        }
    }

@JonB Thank you as well!