stream-chat-flutter/example/lib/custom_message.dart

import 'package:flutter/material.dart';
import 'package:stream_chat_flutter/stream_chat_flutter.dart';

void main() async {
  final client = Client('qk4nn7rpcn75');

  await client.setUser(
    User(id: 'wild-breeze-7'),
    'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyX2lkIjoid2lsZC1icmVlemUtNyJ9.VM2EX1EXOfgqa-bTH_3JzeY0T99ngWzWahSauP3dBMo',
  );

  final channelClient = client.channel('messaging', id: 'godevs');

  // ignore: unawaited_futures
  channelClient.watch();

  runApp(
    StreamChat(
      client: client,
      child: MaterialApp(
        home: StreamChannel(
          channelClient: channelClient,
          child: ChannelPage(),
        ),
      ),
    ),
  );
}

class ChannelPage extends StatelessWidget {
  const ChannelPage({
    Key key,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Expanded(
            child: MessageListView(
              messageBuilder: (context, message, _) {
                final isCurrentUser =
                    StreamChat.of(context).user.id == message.user.id;
                final textAlign =
                    isCurrentUser ? TextAlign.right : TextAlign.left;
                return ListTile(
                  title: Text(
                    message.text,
                    textAlign: textAlign,
                  ),
                  subtitle: Text(
                    message.user.extraData['name'],
                    textAlign: textAlign,
                  ),
                );
              },
            ),
          ),
          MessageInput(),
        ],
      ),
    );
  }
}