Show widget when a node (without children) is expanded

[Uche01]

I think it'd be nice to show an optional widget on node expansion when node's children is empty.

Use case: I need to show a button to add child for the root node when the root node is expanded. I tried a hack of replacing the root node with a custom expandable widget, but this came at the expense of not been able to access the root node's properties.

[SeriousMonk]

You could just build your expansion tiles like this:

AnimatedSize(
	duration: _collapseAnimationDuration, //e.g. const Duration(milliseconds: 250) this should be the same duration as SliverAnimatedTree.duration
	alignment: Alignment.topCenter,
	child: Column(
	  children: [
		ListTile(
			onTap: (){
			  _treeController.toggleExpansion(entry.node);
			},
			title: Text('This is an expansion tile', style: Theme.of(context).textTheme.bodyMedium, maxLines: 3),
		),
		if(entry.isExpanded && entry.node.children.isEmpty) Text('No items')
	  ],
	)
  )