Flutter textformfield error text customization. In this post, I will be implementing Flutter textformfield error text in Flutter textformfield. I will be explaining it step by step using proper Flutter example easy code so you can have a practical and complete understanding of how to change Flutter textformfield error text in Flutter textformfield.
What is Flutter Textformfield Error Text?
Flutter textformfield error text is the text that is shown at bottom left of the Flutter textformfield underline border. It is shown whenever a wrong input is given to the Flutter textformfield. A logic is implemented like in the email field if the user input some blank space inside the email text then we can show the Flutter textformfield error text. Let’s now see how we can show the error text in Flutter textformfield.
Implementing Flutter Textformfield Error Text(All Steps)
To show the Flutter textformfield error text, we have to use the decoration constructor of the Flutter textformfield, then passing it the input decoration class and after that we have to use the error text constructor which takes a string. See the below code:
TextFormField( decoration: InputDecoration( errorText: 'This is the error text', ), )

Step 1
String errorTextvalue = '';
Step 2
onChanged: (value) { setState(() { if (value.contains(' ')) { errorTextvalue = value; } else { errorTextvalue = ''; } }); }
Step 3
errorText: errorTextvalue.isEmpty ? null : 'This is the error text'
Beautiful Flutter Textformfield Design Source Code
import 'package:flutter/material.dart'; void main() { runApp(const MyApp()); } class MyApp extends StatelessWidget { const MyApp({Key? key}) : super(key: key); @override Widget build(BuildContext context) { return MaterialApp( debugShowCheckedModeBanner: false, home: Homepage(), ); } } class Homepage extends StatefulWidget { @override State<Homepage> createState() => _HomepageState(); } class _HomepageState extends State<Homepage> { String errorTextvalue = ''; @override Widget build(BuildContext context) { return SafeArea( child: Scaffold( body: Center( child: Padding( padding: EdgeInsets.symmetric(horizontal: 40), child: TextFormField( onChanged: (value) { setState(() { if (value.contains(' ')) { errorTextvalue = value; } else { errorTextvalue = ''; } }); }, decoration: InputDecoration( border: InputBorder.none, enabledBorder: OutlineInputBorder( borderRadius: BorderRadius.circular(50), borderSide: BorderSide(color: Colors.purple)), focusedBorder: OutlineInputBorder( borderRadius: BorderRadius.circular(50), borderSide: BorderSide(color: Colors.purple)), errorBorder: OutlineInputBorder( borderRadius: BorderRadius.circular(50), borderSide: BorderSide(color: Colors.red)), focusedErrorBorder: OutlineInputBorder( borderRadius: BorderRadius.circular(50), borderSide: BorderSide(color: Colors.red)), errorText: errorTextvalue.isEmpty ? null : 'Don\'t use blank spaces', ), ))), )); } }
Conclusion
In conclusion, we have learned how to implement and customize Flutter textformfield error text logically. I’d enjoy your feedback and encourage you to have a look at my other articles on Flutter app development, Flutter widgets, amazing Flutter templates, Flutter animations and many more, links to some of those articles are listed below. That’s it for this particular post. Thanks for reading.