flutter_flutter/examples/api/lib/widgets/sliver/sliver_tree.0.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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'),
    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'),
      ],
    ),
    TreeSliverNode<String>(
      'Third',
      expanded: true,
      children: <TreeSliverNode<String>>[
        TreeSliverNode<String>('gamma'),
        TreeSliverNode<String>('delta'),
        TreeSliverNode<String>('epsilon'),
      ],
    ),
    TreeSliverNode<String>('Fourth'),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('TreeSliver Demo')),
      body: CustomScrollView(
        slivers: <Widget>[
          TreeSliver<String>(
            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;
                },
          ),
        ],
      ),
    );
  }
}