Highly customizable TextField

my_text_field.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import '../resources/r.dart';

class MyTextField extends StatefulWidget {
  const MyTextField(
    this.label,
    this.onChange, {
    this.iconData,
    this.isPassword = false,
    this.inputType,
    this.onFinish,
    this.isOutlined = true,
    this.suffixText,
    this.isBoldStyle,
    this.errorMessage,
    this.onTap,
  });

  final String label;
  final IconData iconData;
  final void Function(String) onChange;
  final void Function() onFinish;
  final void Function() onTap;
  final bool isPassword;
  final TextInputType inputType;
  final bool isOutlined;
  final String suffixText;
  final bool isBoldStyle;
  final String errorMessage;

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

class _MyTextFieldState extends State<MyTextField> {
  @override
  void initState() {
    super.initState();
    isObscured = widget.isPassword;
  }

  bool isObscured;

  @override
  Widget build(BuildContext context) {
    return TextField(
      decoration: InputDecoration(
        border: widget.isOutlined
            ? OutlineInputBorder(
                borderRadius: BorderRadius.circular(8),
              )
            : UnderlineInputBorder(
                borderRadius: BorderRadius.circular(8),
              ),
        icon: widget.iconData != null
            ? Icon(
                widget.iconData,
                color: primary,
                size: 24,
              )
            : null,
        suffixIcon: widget.isPassword
            ? SizedBox(
                height: 48,
                width: 48,
                child: Center(
                  child: IconButton(
                    icon: Icon(
                      isObscured ? Icons.visibility_off : Icons.visibility,
                    ),
                    onPressed: () => setState(() {
                      isObscured = !isObscured;
                    }),
                  ),
                ),
              )
            : widget.suffixText != null
                ? SizedBox(
                    height: 48,
                    width: 48,
                    child: Center(
                      child: Text(
                        widget.suffixText,
                        style: R.styles.scriptFont.copyWith(
                          color: greyColor,
                        ),
                      ),
                    ),
                  )
                : null,
        labelText: widget.label,
        labelStyle: R.styles.normalFont.copyWith(
          color: greyColor,
          fontWeight: FontWeight.normal,
        ),
        errorText: widget.errorMessage,
        errorStyle: R.styles.normalFont.copyWith(
          color: redColor,
          fontWeight: FontWeight.normal,
        ),
        isDense: true,
        contentPadding: widget.isOutlined
            ? null
            : const EdgeInsets.only(
                top: 0,
                bottom: 8,
                right: 0,
                left: 0,
              ),
      ),
      textAlignVertical: TextAlignVertical.center,
      cursorColor: fontColor,
      style: widget.isBoldStyle != null
          ? R.styles.normalFont.copyWith(fontWeight: FontWeight.bold)
          : R.styles.normalFont,
      obscureText: isObscured,
      keyboardType: widget.isPassword
          ? TextInputType.visiblePassword
          : widget.inputType ?? TextInputType.text,
      textInputAction:
          widget.onFinish != null ? TextInputAction.done : TextInputAction.next,
      onEditingComplete: widget.onFinish != null
          ? () {
              FocusScope.of(context).unfocus();
              widget.onFinish();
            }
          : FocusScope.of(context).nextFocus,
      onChanged: widget.onChange,
      onTap: widget.onTap,
    );
  }
}

NOTE: you need to change the style by yourself! (Color, TextStyle, EdgeInsetsGeometry, etc.)