我有一个文本字段，用户可以在其中输入文本。但当我输入文本并按下“完成”按钮时，遇到了一个问题-文本从文本字段中消失，就像它从未存在过一样。但当字段处于活动状态并输入字符时，所有内容都是可见的。为什么单击“完成”按钮后文本从文本字段中消失？

class CommentWidget extends StatelessWidget {
  final Function(String) onChanged;
  final String? textForm;
  final bool isHelpPage;

  CommentWidget({Key? key, required this.onChanged, required this.textForm, required this.isHelpPage})
      : super(key: key);

  final TextEditingController controller = TextEditingController();
  String value = '';

  @override
  Widget build(BuildContext context) {
    final Size size = MediaQuery.of(context).size;
    controller.text = textForm ?? '';

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        isHelpPage
        ? const SizedBox()
        : const ResizedText(
          'Comments',
          textStyle: constants.Styles.smallTextStyleWhite,
        ),
        SizedBox(
          height: UiSize.getHeight(15, size),
        ),
        Container(
          height: UiSize.getHeight(isHelpPage ? 290 : 150, size),
          width: UiSize.getWidth(360, size),
          decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(8),
            border: Border.all(
              color: constants.Colors.purpleMain,
              width: 0.5,
            ),
          ),
          child: Padding(
            padding: EdgeInsets.only(
              top: UiSize.getHeight(16, size),
              left: UiSize.getWidth(18, size),
              right: UiSize.getWidth(18, size),
              bottom: UiSize.getHeight(16, size),
            ),
            child: TextField(
              maxLines: isHelpPage ? 10 :4,
              maxLength: isHelpPage ? 1500 : 450,
              controller: controller,
              style: constants.Styles.smallerBookTextStyleWhiteOpacity,
              textInputAction: TextInputAction.done,
              onChanged: (text) {
                onChanged(text);
                value = text;
              },
              decoration: InputDecoration(
                border: InputBorder.none,
                helperStyle: constants.Styles.smallerBookTextStyleWhiteOpacity,
                hintStyle: constants.Styles.smallerBookTextStyleWhiteOpacity,
                hintText: 'Here you can describe the problem in more detail',
              ),
            ),
          ),
        ),
      ],
    );
  }
}