Local caching

// First, create a GroupChannelListQuery instance.
final query = GroupChannelListQuery()
  ..order = GroupChannelListQueryOrder.chronological;
  // Acceptable values are chronological, latestLastMessage(default), channelNameAlphabetical and metadataValueAlphabetical.
  // You can add other params setters.

// Second, create MyGroupChannelCollectionHandler instance.
final handler = MyGroupChannelCollectionHandler();
class MyGroupChannelCollectionHandler extends GroupChannelCollectionHandler {
  @override
  void onChannelsAdded(ChannelContext context, List<GroupChannel> channels) {
    // Update widgets with collection.channelList.
  }
  @override
  void onChannelsUpdated(ChannelContext context, List<GroupChannel> channels) {
    // Update widgets with collection.channelList.
  }
  @override
  void onChannelsDeleted(ChannelContext context, List<String> deletedChannelUrls) {
    // Update widgets with collection.channelList.
  }
}

// Create a GroupChannelCollection instance.
final collection = GroupChannelCollection(query: query, handler: handler);

// Load channels.
try {
  // Check whether there are more channels to load before calling loadMore().
  if (collection.hasMore) {
      await collection.loadMore();
  }
} catch (e) {
  // Handle error.
}

// Clear the collection.
collection.dispose();

final collection = MessageCollection(
  channel: channel,
  params: MessageListParams(),
  handler: MyMessageCollectionHandler(),
  startingPoint: SendbirdChat.maxInt,
);

class MyMessageCollectionHandler extends MessageCollectionHandler {
  @override
  void onMessagesAdded(MessageContext context, GroupChannel channel, List<BaseMessage> messages) {
    // Update widgets with collection.messageList.
  }
  @override
  void onMessagesUpdated(MessageContext context, GroupChannel channel, List<BaseMessage> messages) {
    // Update widgets with collection.messageList.
  }
  @override
  void onMessagesDeleted(MessageContext context, GroupChannel channel, List<BaseMessage> messages) {
    // Update widgets with collection.messageList.
  }
  @override
  void onChannelUpdated(ChannelContext context, GroupChannel channel) {
    // Update widgets with collection.messageList.
  }
  @override
  void onChannelDeleted(ChannelContext context, String deletedChannelUrl) {
    // Back to the previous page.
  }
  @override
  void onHugeGapDetected() {
    // The Chat SDK detects that more than 300 messages are missing.
    collection.dispose();        // Dispose the collection.
    createMessageCollection();   // Create a new message collection object.
    // An additional implementation is required for initialization.
  }
}

// Initialize messages from startingPoint.
try {
  // Initialize messages from the startingPoint.
  await collection.initialize();
  // Messages are retrieved through API calls from the Sendbird server.
} catch (e) {
  // Handle error.
}

// Load previous messages.
try {
  // Load the previous messages
  // when the scroll reaches the first message in the chat view.
  if (collection.hasPrevious) {
      await collection.loadPrevious();
  }
} catch (e) {
  // Handle error.
}

// Load the next set of messages.
try {
  // Load the next set of messages
  // when the scroll reaches the last message in the chat view.
  if (collection.hasNext) {
      await collection.loadNext();
  }
} catch (e) {
  // Handle error.
}

// Clear the collection.
collection.dispose();

if (message.sendingStatus == SendingStatus.failed) {
  if (message is UserMessage) {
    // Resend a user message.
    messageCollection.channel.resendUserMessage(message);
  } else if (message is FileMessage) {
    // Resend a file message.
    messageCollection.channel.resendFileMessage(message);
  }
}

final cachedDataSize = await SendbirdChat.getCachedDataSize();
await SendbirdChat.clearCachedData();
await SendbirdChat.clearCachedMessages('CHANNEL_URL');

// These should be used for displaying pending messages in the chat view.
final userMesageParams = userMessage.messageCreateParams;
final fileMessageParams = fileMessage.messageCreateParams;