在flutter中为表单字段和控制器构建包装器小部件

class FormFieldWrapper extends StatefulWidget {
  final TextEditingController controller;
  final String labelText;
  
  FormFieldWrapper({required this.controller, required this.labelText});

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

class _FormFieldWrapperState extends State<FormFieldWrapper> {
  String? errorText;

  void validateInput(String? value) {
    setState(() {
      // Perform input validation here
      if (value == null || value.isEmpty) {
        errorText = 'Field cannot be empty';
      } else {
        errorText = null;
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        TextFormField(
          controller: widget.controller,
          onChanged: validateInput,
          decoration: InputDecoration(
            labelText: widget.labelText,
            errorText: errorText,
          ),
        ),
        SizedBox(height: 10),
        ElevatedButton(
          onPressed: () {
            // Handle form submission here
            if (errorText == null) {
              // Form is valid, perform further processing
              String value = widget.controller.text;
              // Do something with the value
            }
          },
          child: Text('Submit'),
        ),
      ],
    );
  }
}