Widget _buildDefaultTreeSelect(BuildContext context) {
    var options = <TDSelectOption>[];

    for (var i = 1; i <= 10; i++) {
      options.add(TDSelectOption(label: '选项$i', value: i, children: []));

      for (var j = 1; j <= 10; j++) {
        options[i - 1].children.add(
            TDSelectOption(label: '选项$i.$j', value: i * 10 + j, children: []));
      }
    }

    return TDTreeSelect(
      options: options,
      defaultValue: values1,
      onChange: (val, level) {
        print('$val, $level');
      },
    );
  }