How can we change the font Size of the error message of TextFormField

Question

` TextFormField( maxLength: 50,

              decoration: const InputDecoration(label: Text('Name')),
              keyboardType: TextInputType.text,
              validator: (value) {
                if (value == null ||
                    value.isEmpty ||
                    value.trim().length <= 1 ||
                    value.trim().length > 50) {
                  return "Must be between 1 and 50 characters";
                }
                return null;
              },
            ),`

Error message font size

Answer 1

You use the errorStyle parameter of the inputdecorationtheme:

import 'package:flutter/material.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        inputDecorationTheme: const InputDecorationTheme(
          errorStyle: TextStyle(
            color: Colors.red,
            fontSize: 32,
          ),
        ),
      ),
      home: const MyForm(),
    );
  }
}

class MyForm extends StatefulWidget {
  const MyForm({super.key});

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

class _MyFormState extends State<MyForm> {
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Padding(
          padding: const EdgeInsets.all(32),
          child: Form(
            key: _formKey,
            child: Column(
              children: [
                TextFormField(
                  validator: (value) {
                    if (value!.isEmpty) {
                      return 'Please enter some text';
                    }
                    return null; // Indicates no error
                  },
                ),
                ElevatedButton(
                  onPressed: () {
                    if (_formKey.currentState!.validate()) {
                      // Form is valid, do something
                    }
                  },
                  child: const Text('Submit'),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}