Flutter - StatefulBuilder中的TextField在modalBottomSheet中无法正常工作

void _showModalBottomSheet(BuildContext context) {
  showModalBottomSheet(
    context: context,
    builder: (BuildContext context) {
      return StatefulBuilder(
        builder: (BuildContext context, StateSetter setState) {
          FocusNode focusNode = FocusNode();

          return Container(
            padding: EdgeInsets.all(16.0),
            child: Column(
              children: [
                TextField(
                  focusNode: focusNode,
                  onChanged: (value) {
                    // 处理文本变化
                  },
                ),
                RaisedButton(
                  onPressed: () {
                    // 处理按钮点击事件
                  },
                  child: Text('Submit'),
                ),
              ],
            ),
          );
        },
      );
    },
  );
}