Simple way to expand all nodes on a QTreeView?

[Pieter from Belgium]

[Answering to my self, but also to the original asker:]

Maybe a more elegant solution for keeping rows expanded by default is by reimplementing the following method:

void QAbstractItemView::rowsInserted ( const QModelIndex & parent, int start, int end )

In the reimplementation, besides the super class effect, explicitly expand all collapsed rows that were inserted [as well as their children that may already be present]...

(However, it would be nice if in a future version of Qt, automatically managing such properties would be present -- like also automatically resizing columns. This of course unless explicitly overruled by the user (e.g. reducing the column with interactively, or collapsing an item interactively.)

[Pieter from Belgium]

Hehe, thinking the same thing at the same time . However I must admit you put it more concise, and with the correct references.

QTreeView::itemsExpandable [as referred to in the feature rejection] does not help in this issue, as it can only be used to prevent the default collapsed item to be expanded...

[fullmetalcoder]

Qt 4.2 introduced QTreeView::expandAll(). Ain't that neat? And the feature reject mentions it BTW...

[jpn]

Qt 4.2 introduced QTreeView::expandAll(). Ain't that neat? And the feature reject mentions it BTW...

The point is that it's very expensive to call it for large models.

Warning: if the model contains a large number of items, this function will be take time to execute.

Now, consider a dynamically changing large model. You don't want to call QTreeView::expandAll() again and again, do you?

[evgeniy]

void MainWindow::expandNode(const QModelIndex &parentIndex, bool expand) {
  tree->setExpanded(parentIndex, expand);
  for (qint32 rowNum = 0; rowNum < treeModel->rowCount(parentIndex); ++rowNum) {
    QModelIndex childIndex = treeModel->index(rowNum, 0, parentIndex);
    tree->setExpanded(childIndex, expand);
    expandNode(childIndex);
  }
}

void MainWindow::expandNode(const QModelIndex &parentIndex, bool expand) {
  tree->setExpanded(parentIndex, expand);
  for (qint32 rowNum = 0; rowNum < treeModel->rowCount(parentIndex); ++rowNum) {
    QModelIndex childIndex = treeModel->index(rowNum, 0, parentIndex);
    tree->setExpanded(childIndex, expand);
    expandNode(childIndex);
  }
}

To copy to clipboard, switch view to plain text mode