Recursively expand all child items of item in QTreeView

Question

I have a QTreeView and I want to expand all child items of a recently expanded item.

I tried using .expandAll(), but it expand all others items also.

I'm having a hard time to get the ModelIndex of the item that was lastly expanded, If i do have it I can recursively expand it's children.

How do I do that?

Hiroshima

Answer 1

To expand all nodes below the given one, I would do it recursively in the following way (C++):

void expandChildren(const QModelIndex &index, QTreeView *view)
{
    if (!index.isValid()) {
        return;
    }

    int childCount = index.model()->rowCount(index);
    for (int i = 0; i < childCount; i++) {
        const QModelIndex &child = index.child(i, 0);
        // Recursively call the function for each child node.
        expandChildren(child, view);
    }

    if (!view->expanded(index)) {
        view->expand(index);
    }
}

Gaeta

But how do I get the initial QModelIndex? – Hiroshima

@f.rodrigues, what is the use model? How do you need to expand it? By clicking on a node? – Gaeta

The model is a QStandardItemModel(), and a node is expanded by clicking in it. – Hiroshima

@f.rodrigues, ok, than handle the QAbstractItemView::clicked() signal of your tree view and you will get the initial index of the clicked node. – Gaeta

The clicked only gives emits its signal when I click on the name, not on the decorator '>' beside it. – Hiroshima

@f.rodrigues, what about QTreeView::expanded() signal instead? But be careful, because the expandChildren() function I proposed will cause the expanded signal emition too. – Gaeta

Oh yeah, the expanded worked, I was using it, but with a lambda and it was losing the index in the process. – Hiroshima

Working fine, just a minor complain. The animation of the expanding is complety gone, is there a way to fix this? – Hiroshima

@Hiroshima Getting animations working is probably worthy of another question on SO. I have an idea, but way to long to post in the comments of another answer. – Pipistrelle

Should it not be view->isExpanded (Qt 5.6) and do you really think calling it is more efficient than just calling expand? – Asaph

@DaRich, expand is already optimised for the case that the tree item is expanded. So the check is not necessary. – Blenheim

Answer 2

Starting from Qt 5.13 QTreeView::expandRecursively is available

Shropshire