Flutter - Collapsing ExpansionTile after choosing an item

Question

I\'m trying to get ExpansionTile to collapse after I choose an item, but it does not close the list that was opened.

I tried to use the onExpansio

Answer 1

I've made a TreeView widget. It uses ExpansionTile to simulate the hierarchy. Each ExpansionTile could host a collection of ExpansionTile which can host ...etc.

Everything worked fine until I wanted to add 2 features : expand all / collapse all. What helped me to overcame this problem is the GlobalKey.

My TreeView widget, is hosted in a page and is used with a global key. I expose a VoidCallback. The implementation sets a new key in the setState method.

// TreeView host page
GlobalKey _key = GlobalKey();
void redrawWidgetCallback() {
    setState(() {
      // Triggers a rebuild of the whole TreeView.
      _key = GlobalKey();
    });
}
[...]
// In the Scaffold body :
TreeView(
    key: _key,
    treeViewItems: widget.treeViewItems,
    redrawWidgetCallback: redrawWidgetCallback,
  )

Then in my collapse/expand method in the widget, at the end, I call widget.redrawWidgetCallback. No need to deal with a key for each level of the treeView : the root element widget is enough.

It may have perf issues / not the right way to go. But since my TreeView won't be used with more than 50 nodes, it's ok for me until I found a better solution which doesn't involve to create an ExpandableTile because I believe this behavior will be available oneday on the ExpansionTile itself.

PS : notice that this workaround doesn't run the expand animation.