RangeError (index): Invalid value: Valid value range is empty: 0 Error Flutter - flutter

Question

Can you please tell me what's the issue with my code and how to avoid showing that red screen error in my app?
════════ Exception caught by widgets library ═══════════════════════════════════
The following RangeError was thrown building ChatMessage(dirty):
RangeError (index): Invalid value: Valid value range is empty: 0
My Code:
import 'package:crypto_app/models/users.dart';
import 'package:crypto_app/pages/login.dart';
import 'package:crypto_app/services/firestoreservice.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:meta/meta.dart';
void main() {
runApp(
FriendlyChatApp(),
);
}
final ThemeData kIOSTheme = ThemeData(
primarySwatch: Colors.blue,
primaryColor: Colors.grey[100],
primaryColorBrightness: Brightness.light,
);
final ThemeData kDefaultTheme = ThemeData(
primarySwatch: Colors.orange,
accentColor: Colors.orangeAccent,
);
String _name = '';
class FriendlyChatApp extends StatelessWidget {
const FriendlyChatApp({
Key key,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: ChatScreen(),
);
}
}
class ChatMessage extends StatelessWidget {
ChatMessage({this.text, this.animationController});
final String text;
final AnimationController animationController;
#override
Widget build(BuildContext context) {
return SizeTransition(
sizeFactor:
CurvedAnimation(parent: animationController, curve: Curves.easeOut),
axisAlignment: 0.0,
child: Container(
margin: EdgeInsets.symmetric(vertical: 10.0),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Container(
margin: const EdgeInsets.only(right: 16.0),
child: CircleAvatar(child: Text(_name[0])),
),
Expanded(
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(_name, style: Theme.of(context).textTheme.headline4),
Container(
margin: EdgeInsets.only(top: 5.0),
child: Text(text),
),
],
),
),
],
),
),
);
}
}
class ChatScreen extends StatefulWidget {
#override
_ChatScreenState createState() => _ChatScreenState();
}
class _ChatScreenState extends State<ChatScreen> with TickerProviderStateMixin {
final List<ChatMessage> _messages = [];
final _textController = TextEditingController();
final FocusNode _focusNode = FocusNode();
bool _isComposing = false;
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
decoration: Theme.of(context).platform == TargetPlatform.iOS //new
? BoxDecoration(
border: Border(
top: BorderSide(color: Colors.grey[200]),
),
)
: null,
child: Column(
children: [
Flexible(
child: ListView.builder(
padding: EdgeInsets.all(8.0),
reverse: true,
itemBuilder: (_, int index) => _messages[index],
itemCount: _messages.length,
),
),
Divider(height: 1.0),
Container(
decoration: BoxDecoration(color: Theme.of(context).cardColor),
child: _buildTextComposer(),
),
],
),
),
);
}
Widget _buildTextComposer() {
return IconTheme(
data: IconThemeData(color: Theme.of(context).accentColor),
child: Container(
margin: EdgeInsets.symmetric(horizontal: 8.0),
child: Row(
children: [
Flexible(
child: TextField(
controller: _textController,
onChanged: (String text) {
setState(() {
_isComposing = text.isNotEmpty;
});
},
onSubmitted: _isComposing ? _handleSubmitted : null,
decoration: InputDecoration.collapsed(
hintText: 'Mesajınızı Buraya Yazınız:'),
focusNode: _focusNode,
),
),
Container(
margin: EdgeInsets.symmetric(horizontal: 4.0),
child: Theme.of(context).platform == TargetPlatform.iOS
? CupertinoButton(
onPressed: _isComposing
? () => _handleSubmitted(_textController.text)
: null,
child: Text('Gönder'),
)
: IconButton(
icon: const Icon(Icons.send),
onPressed: _isComposing
? () => _handleSubmitted(_textController.text)
: null,
))
],
),
),
);
}
void _handleSubmitted(String text) {
_textController.clear();
setState(() {
_isComposing = false;
});
var message = ChatMessage(
text: text,
animationController: AnimationController(
duration: const Duration(milliseconds: 700),
vsync: this,
),
);
setState(() {
_messages.insert(0, message);
});
_focusNode.requestFocus();
message.animationController.forward();
}
#override
void dispose() {
for (var message in _messages) {
message.animationController.dispose();
}
super.dispose();
}
}

Answer 1

The issue is happening because of this line:
CircleAvatar(child: Text(_name[0])),
You've declared the variable as:
String _name = '';
You are trying to access the first character of an empty string using the index. To fix the issue set some value to that variable:
String _name = 'Random';