Get a tree view of the dir you provide or the current dir you are in.

main.dart

/// Used package https://pub.dev/packages/flutter_simple_treeview
/// and https://pub.dev/packages/url_launcher to open the file
class FileTreeItem {
  final String name;
  final String path;
  final List<FileTreeItem>? children;

  FileTreeItem({required this.name, this.children, required this.path});
}

List<FileTreeItem> getFileTreeDir([Directory? dir]) {
  final separator = Platform.pathSeparator;
  dir ??= Directory.current;
  final dirList = dir.listSync();
  return dirList.map((FileSystemEntity entity) {
    final path = entity.path;
    final name = path.split(separator).last;
    if (entity is Directory) {
      return FileTreeItem(name: name, children: getFileTreeDir(entity), path: path);
    } else {
      return FileTreeItem(name: name, path: path);
    }
  }).toList();
}

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

  @override
  _TreeFromJsonState createState() => _TreeFromJsonState();
}

class _TreeFromJsonState extends State<TreeFromJson> {
  final TreeController _treeController = TreeController(allNodesExpanded: false);
  final tree = getFileTreeDir();

  @override
  Widget build(BuildContext context) {
    return SingleChildScrollView(
      child: TreeView(
        nodes: toTreeNodes(tree),
        treeController: _treeController,
      ),
    );
  }

  List<TreeNode> toTreeNodes(List<FileTreeItem> tree) {
    List<TreeNode> nodes = [];
    for (var treeItem in tree) {
      final key = ObjectKey(treeItem.name);
      if (treeItem.children != null) {
        nodes.add(
          TreeNode(
            key: key,
            content: InkWell(
              onTap: () => setState(() => _treeController.toggleNodeExpanded(key)),
              child: Center(child: Text(treeItem.name)),
            ),
            children: toTreeNodes(treeItem.children!),
          ),
        );
      } else {
        nodes.add(
          TreeNode(
            key: key,
            content: InkWell(
              onTap: () => launchUrlString(treeItem.path),
              child: Center(child: Text(treeItem.name)),
            ),
          ),
        );
      }
    }
    nodes.sort((a, b) => a.children?.isNotEmpty ?? false ? -1 : 1);
    return nodes;
  }
}