Flutter onChange Not Working on My TextField

I created a re-usable textfield for my Flutter project but the OnChange method is not working with the re-usable widget. Whenever I tried creating the field directly on the project it works. I am suspecting that the value option that comes with the Textfield onChange is likely the reason for the error. Any help with a solution?

class NumberOnlyTextField extends StatelessWidget{
  final controller;
  final String hintText;
  final bool obscureText;
  final bool enableTxtField;
  final Function()? onChanged;

  const NumberOnlyTextField({
    super.key,
    required this.controller,
    required this.hintText,
    required this.obscureText,
    required this.enableTxtField,
    required this.onChanged,
  });

  @override 
  Widget build(BuildContext context){
    return Padding(
      padding: const EdgeInsets.symmetric(horizontal: 15.0),
      child: Container(
        decoration: BoxDecoration(
          color: Colors.white,
          border: Border.all(color: const Color.fromARGB(255, 213, 211, 211)),
          borderRadius: BorderRadius.circular(4),
        ),
        child: Padding(
          padding: const EdgeInsets.only(left: 10.0, right: 10.0),
          child: TextField(
            controller: controller,
            onChanged: (value) { onChanged; },
            obscureText: obscureText,
            enabled: enableTxtField,
            keyboardType: TextInputType.number,
            inputFormatters: [
              FilteringTextInputFormatter.allow(
                RegExp('[0-9]+.?[0-9]*'),
              ),
            ],
            decoration: InputDecoration(
              border: InputBorder.none,
              hintText: hintText,
              hintStyle: TextStyle(color: Colors.grey[500]),
            ),
          ),
        ),
      ),
    );
  }
}

Here is where it is used on another page:

      //Amount
      NumberOnlyTextField(
        controller: amountXController,
        onChanged: validateAmount(),
        hintText: 'Amount',
        obscureText: false,
        enableTxtField: true,
      ),
      const SizedBox(height: 10),