How to get clicked item index of QScrollArea?

BushyAxis793

Hello. I have a problem. How can I get an index of item in QScrollArea?

This is my code:

    QWidget *widget = new QWidget();
    ui->scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
    ui->scrollArea->setWidgetResizable(true);
    ui->scrollArea->setWidget(widget);
    widget->setLayout(Vlayout);

I have some custom widgets added to QVBoxLayout:

Vlayout->addWidget(operationWidget);

Result:

And I would like to set each of my widget as checked (highlighted). So I decided to use event filter:

ui->scrollArea->viewport()->installEventFilter(this);

bool QueriesCreator::eventFilter(QObject *object, QEvent *event)
{
if(object == ui->scrollArea->viewport() && event->type()==QEvent::MouseButtonRelease)
    {
        QMouseEvent * mouseEvent = static_cast< QMouseEvent * >( event );

        if( mouseEvent->button() == Qt::LeftButton ) {

            if(Vlayout->count()>0)
            {
                QWidget *widget = childAt(mouseEvent->pos());


                int index = Vlayout->layout()->indexOf(widget);
                qDebug()<<index;
                if(index>=0)
                {
                    QLayoutItem* const item = Vlayout->layout()->itemAt(index);
                    auto widget = dynamic_cast<OperationWidget*>(item);
                    
                }
            }

            return true;
        }
        else
            return false;
    }

    return false;

}

And the index I get is -1. I don't know why. If you have any idea how to get index of clicked QScrollArea element. I will be very thankfull. Have a good day.

SGaist

Hi,

You are likely getting one of the subwidget of your "items".

From the looks of it, using a QListView with a QStyledItemDelegate would be simpler and you would have the highlighting easier to handle.

Chris Kawa

@BushyAxis793 You're probably clicking on a sub widget, so indexOf will not find it. You can find your widget easier by going through the parents of what was clicked and avoiding the indexing and dynamic casts:

...
QWidget *widget = childAt(mouseEvent->pos());

// go up parent chain until you find OperationWidget
while(widget && !widget->metaObject()->inherits(&OperationWidget::staticMetaObject))
     widget = widget->parentWidget();

if (widget)
{
   OperationWidget* op = qobject_cast<OperationWidget*>(widget);
   // do something with op
}
else
{
   // not found, probably clicked between widgets
}

JonB

@Chris-Kawa said in How to get clicked item index of QScrollArea?:

!widget->metaObject()->inherits(&OperationWidget::staticMetaObject)

What's this bit Chris? I can guess this is how you recognise the root of the widget tree?

Chris Kawa

@JonB The loop is pretty much just "while widget is not OperationWidget check parent".
This

widget->metaObject()->inherits(&OperationWidget::staticMetaObject)

is pretty much the same as

dynamic_cast<OperationWidget*>(widget) != nullptr

just QObject specific. I guess you can also write that loop as

while (widget && !qobject_cast<OperationWidget*>(widget))

if you don't fancy the metaObject stuff directly (qobject_cast does that internally).

mpergand

@Chris-Kawa said in How to get clicked item index of QScrollArea?:

widget->metaObject()->inherits(&OperationWidget::staticMetaObject)

or
widget->inherits("OperationWidget")

Chris Kawa

@mpergand I have an acquired distaste for string based APIs, so I intentionally try not to mention them whenever I can :) But yeah, you could do that and then rename the class while forgetting to also change the string and wonder what's happening. To each their own :)

mpergand

@Chris-Kawa said in How to get clicked item index of QScrollArea?:

I have an acquired distaste for string based APIs,

OK, cut the apple in two :)
widget->inherits(OperationWidget::staticMetaObject.className())

Anyway, I don't see any reason for not using qobject_cast here.

JonB

@mpergand said in How to get clicked item index of QScrollArea?:

Anyway, I don't see any reason for not using qobject_cast here.

+1 :)

BushyAxis793

@SGaist I supposed it too. However here: https://forum.qt.io/topic/142288/how-can-i-add-custom-widget-to-qlistview/15

I tried to create model/view but without result. So I decided to looking for new ideas which would be good for me. All I want is some features:

Highlight my widget
Double clik on my widget
Change order (move up/down) of my witgets list

I hope I will find solution.

SGaist

You do realize that you are trying to reimplement the model/view paradigm rather than implementing a delegate that should paint three strings ?