这是密码代码：

class ThemeChangerWidget extends StatelessWidget {
  final List<String> string = ['Light', 'Dark', 'Amoled'];
  @override
  Widget build(BuildContext context) {
  final stateData = Provider.of<ThemeNotifier>(context);
  final ThemeData state = stateData.getTheme();

  return Theme(
  data: state.copyWith(unselectedWidgetColor: state.accentColor),
  child: AlertDialog(
      backgroundColor: state.primaryColor,
      shape:
          RoundedRectangleBorder(borderRadius: BorderRadius.circular(8.0)),
      title: Text('Select Theme', style: state.textTheme.body1),
      content: ListView.builder(
        shrinkWrap: true,
        itemBuilder: (context, index) {
          return RadioListTile(
            value: index,
            groupValue: themes.indexOf(state),
            onChanged: (ind) {
              onThemeChanged(ind, stateData);
            },
            title: Text(
              string[index],
              style: state.textTheme.body2,
            ),
          );
        },
        itemCount: string.length,
      )),
      );
     }
     }'

errors-在performLayout（）过程中引发了以下Assert：
RenderShrinkWrappingViewport不支持返回内部尺寸。
有时抛出此错误而不是高于LayoutBuilder does not support returning intrinsic dimensions.
计算固有尺寸需要示例化视口的每个子对象，这就消除了视口懒惰的缺点。如果您只是尝试在主轴方向上对视口进行包络处理，则应该能够通过仅为视口提供宽松的约束来实现该效果，而无需测量其内部尺寸。