Create custom textformfield

Question

I am trying to create custom textformfield so I can easily style only in one place. But currently I am stuck on how to pass validation and save process. Can someone give me a working example of custom widget textformfield that I can use? I have been searching it for whole day and cannot find one. Thank you for help.

Example here is on raised button:

import 'package:flutter/material.dart';
import 'package:wkndr/resources/constants.dart';

class CustomButton extends StatelessWidget {
  CustomButton({@required this.text, @required this.onPressed});

  final String text;
  final GestureTapCallback onPressed;

  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      color: colorPrimary,
      child: Text(text, style: TextStyle(fontSize: 17.0, color: colorWhite)),
      onPressed: onPressed,
      shape: new RoundedRectangleBorder(
          borderRadius: new BorderRadius.circular(30.0)),
    );
  }
}

Calling custom raised button:

final _signUpButton = Container(
      child: CustomButton(
          text: sign_up,
          onPressed: () {
            _signUp();
          }),
    );

Answer 1

Instead of making custom TextFormField, you can create a common InputDecoration for styling

class CommonStyle {
  static InputDecoration textFieldStyle({
    String labelTextStr = "",
    String hintTextStr = "",
  }) {
    return InputDecoration(
      contentPadding: EdgeInsets.all(12),
      labelText: labelTextStr,
      hintText: hintTextStr,
      border: OutlineInputBorder(
        borderRadius: BorderRadius.circular(10),
      ),
    );
  }
}

Example:

TextFormField(
  controller: usernameController,
  keyboardType: TextInputType.text,
  textInputAction: TextInputAction.next,
  focusNode: userFocus,
  onFieldSubmitted: (_) {
    FocusScope.of(context).requestFocus(passFocus);
  },
  validator: (value) => emptyValidation(value),
  decoration: CommonStyle.textFieldStyle(
    labelTextStr: "Username",
    hintTextStr: "Enter Username",
  ),
)