TreeSliver first node visual bug while collapsing/expanding #188305

import 'package:flutter/material.dart';

/// Flutter code sample for [TreeSliver].

void main() => runApp(const TreeSliverExampleApp());

class TreeSliverExampleApp extends StatelessWidget {
  const TreeSliverExampleApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(home: TreeSliverExample());
  }
}

class TreeSliverExample extends StatefulWidget {
  const TreeSliverExample({super.key});

  @override
  State<TreeSliverExample> createState() => _TreeSliverExampleState();
}

class _TreeSliverExampleState extends State<TreeSliverExample> {
  TreeSliverNode<String>? _selectedNode;
  final TreeSliverController controller = TreeSliverController();
  final List<TreeSliverNode<String>> _tree = <TreeSliverNode<String>>[
    TreeSliverNode<String>(
      'First',
      children: <TreeSliverNode<String>>[
        TreeSliverNode<String>(
          'alpha',
          children: <TreeSliverNode<String>>[
            TreeSliverNode<String>('uno'),
            TreeSliverNode<String>('dos'),
            TreeSliverNode<String>('tres'),
          ],
        ),
        TreeSliverNode<String>('beta'),
        TreeSliverNode<String>('kappa'),
      ],
    ),
    TreeSliverNode<String>(
      'Second',
      children: <TreeSliverNode<String>>[
        TreeSliverNode<String>(
          'alpha',
          children: <TreeSliverNode<String>>[
            TreeSliverNode<String>('uno'),
            TreeSliverNode<String>('dos'),
            TreeSliverNode<String>('tres'),
          ],
        ),
        TreeSliverNode<String>('beta'),
        TreeSliverNode<String>('kappa'),
      ],
    ),
   
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('TreeSliver Demo')),
      body: CustomScrollView(
        slivers: <Widget>[
          TreeSliver<String>(
           toggleAnimationStyle: AnimationStyle(
              duration: Duration(seconds: 1),
              reverseDuration: Duration(seconds: 1),
            ),
            tree: _tree,
            controller: controller,
            treeNodeBuilder:
                (
                  BuildContext context,
                  TreeSliverNode<Object?> node,
                  AnimationStyle animationStyle,
                ) {
                  Widget child = GestureDetector(
                    behavior: HitTestBehavior.translucent,
                    onTap: () {
                      setState(() {
                        controller.toggleNode(node);
                        _selectedNode = node as TreeSliverNode<String>;
                      });
                    },
                    child: TreeSliver.defaultTreeNodeBuilder(
                      context,
                      node,
                      animationStyle,
                    ),
                  );
                  if (_selectedNode == node as TreeSliverNode<String>) {
                    child = ColoredBox(
                      color: Colors.purple[100]!,
                      child: child,
                    );
                  }
                  return child;
                },
          ),
        ],
      ),
    );
  }
}