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

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

/// Fifth step of the [tutorial](https://getstream.io/chat/flutter/tutorial/)
///
/// Customizing how messages are rendered is another very common use-case that the SDK supports easily.
///
/// Replace the built-in message component with your own is done by passing it as a builder function to the [MessageListView] widget.
///
/// The message builder function will get the usual [BuildContext] argument as well as the [Message] object and its position inside the list.
///
/// If you look at the code you can see that we use [StreamChat.of] to retrieve the current user so that we can style messages own messages in a different way.
///
/// Since custom widgets and builders are always children of [StreamChat] or part of a [Channel],
/// you can use [StreamChat.of], [StreamChannel.of] and [StreamChatTheme.of] to use the API client directly
/// or to retrieve outer scope needed such as messages from the [Channel.state].
void main() async {
  final client = Client(
    's2dxdhpxd94g',
    logLevel: Level.INFO,
  );

  await client.setUser(
    User(id: 'super-band-9'),
    'eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJ1c2VyX2lkIjoic3VwZXItYmFuZC05In0.0L6lGoeLwkz0aZRUcpZKsvaXtNEDHBcezVTZ0oPq40A',
  );

  runApp(MyApp(client));
}

class MyApp extends StatelessWidget {
  final Client client;

  MyApp(this.client);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      builder: (context, child) => StreamChat(
        child: child,
        client: client,
      ),
      home: Container(
        child: ChannelListPage(),
      ),
    );
  }
}

class ChannelListPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: ChannelsBloc(
        child: ChannelListView(
          filter: {
            'members': {
              '\$in': [StreamChat.of(context).user.id],
            }
          },
          sort: [SortOption('last_message_at')],
          pagination: PaginationParams(
            limit: 20,
          ),
          channelWidget: ChannelPage(),
        ),
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: ChannelHeader(),
      body: Column(
        children: <Widget>[
          Expanded(
            child: MessageListView(
              messageBuilder: _messageBuilder,
            ),
          ),
          MessageInput(),
        ],
      ),
    );
  }

  Widget _messageBuilder(
    BuildContext context,
    MessageDetails details,
    List<Message> messages,
  ) {
    final message = details.message;
    final color = details.isMyMessage ? Colors.blueGrey : Colors.blue;
    return MessageWidget(
      message: message,
      messageTheme: details.isMyMessage
          ? StreamChatTheme.of(context).ownMessageTheme
          : StreamChatTheme.of(context).otherMessageTheme,
      borderSide: BorderSide(
        color: color,
        width: 2,
      ),
      padding: const EdgeInsets.all(2),
      attachmentBorderSide: BorderSide(
        color: color,
        width: 2,
      ),
      attachmentPadding: EdgeInsets.all(8),
      borderRadiusGeometry: BorderRadius.vertical(
        top: !details.isLastUser ? Radius.circular(16) : Radius.zero,
        bottom: !details.isNextUser ? Radius.circular(16) : Radius.zero,
      ),
      showSendingIndicator: DisplayWidget.gone,
      reverse: false,
      showUserAvatar:
          details.isNextUser ? DisplayWidget.hide : DisplayWidget.show,
      showTimestamp: !details.isNextUser,
      showUsername: !details.isNextUser,
      showReactions: false,
      showReplyIndicator: false,
    );
  }
}