This page shows you how to build a local cache using a database. This has several advantages like storing raw data in a file and enabling particular queries on stored channels and messages. The content is provided on the assumption that you use SQLite database as a local storage, you can easily follow these steps with any other database like Realm.
In order to enable you to store Sendbird objects such as messages, channels, and users in a local storage, we provide serialization and deserialization methods through our Chat SDK.
By using the serialize() method to convert a Sendbird object to binary data like the following, you can store the data natively in your persistent database.
byte[] data = baseMessage.serialize();
BaseMessage deserializedMessage = BaseMessage.buildFromSerializedData(data);
Save and load messages with serialization and deserialization
After fetching new messages by using a MessageListQuery, serialize and insert each message into your database. However, we recommend that you store the message ID, timestamp, and channel URL in separate columns by using message.getMessageId(), message.getCreatedAt(), and message.getChannelUrl(). This allows you to query the data on a row-by-row basis later on.
Before loading messages in a channel, sort rows in the chronological order by message_ts. Then, deserialize each message and display them in your UI.
When loading previous messages that are not currently stored in the local database, obtain the timestamp of the earliest stored message. Then, query for messages created before that value.
Likewise, when loading new messages, query for messages with a later timestamp than the most recent message.
Note: To keep your local database in sync with Sendbird server’s data, your app should regularly check for changes made to messages in the server and apply those changes to the local cache accordingly. Because the getMessageChangeLogsByToken() and getMessageChangeLogsByTimestamp() methods are deprecated as of August 2021, you can manage local database updates by retrieving change logs of messages using the getMessageChangeLogsSinceToken() or getMessageChangeLogsSinceTimestamp() methods.
// Loading messages from your local database.
final SQLiteDatabase database = dbHelper.getWritableDatabase();
String selection = COLUMN_NAME_CHANNEL_URL + " = ?";
String[] selectionArgs = { CURRENT_CHANNEL_URL };
String sortOrder = COLUMN_NAME_TIMESTAMP + " DESC";
Cursor cursor = database.query(
TABLE_NAME,
null, // The columns to return; all if null.
selection, // The columns for the WHERE clause
selectionArgs, // The values for the WHERE clause
null, // Don't group the rows.
null, // Don't filter by row groups.
sortOrder, // The sort order
"30" // The maximum number of returned results
);
// Creating a list of `BaseMessage` objects by deserializing each.
List<BaseMessage> prevMessageList = new ArrayList<>();
while (cursor.moveToNext()) {
byte[] data = cursor.getBlob(cursor.getColumnIndex(COLUMN_NAME_PAYLOAD));
BaseMessage message = BaseMessage.buildFromSerializedData(data);
prevMessageList.add(message);
}
cursor.close();
// Pass messages to adapter for displaying them in a RecyclerView, ListView, and so on.
mMessageListAdapter.addMessages(prevMessageList);
// Fetching new messages from Sendbird server.
long latestStoredTs = prevMessageList.get(0).getCreatedAt(); // Get the timestamp of the last stored message.
MessageListQuery listQuery = mChannel.createMessageListQuery();
listQuery.next(latestStoredTs, 30, false, new MessageListQuery.MessageListQueryResult() {
@Override
public void onResult(List<BaseMessage> list, SendBirdException e) {
if (e != null) {
// Handle error.
}
// New messages successfully fetched.
mMessageListAdapter.addMessages(list);
// Insert each new message into your local database.
for (BaseMessage message : list) {
// Store each new message into the local database.
ContentValues values = new ContentValues();
values.put(COLUMN_NAME_ID, message.getMessageId());
values.put(COLUMN_NAME_CHANNEL_URL, message.getChannelUrl());
values.put(COLUMN_NAME_TIMESTAMP, message.getCreatedAt());
values.put(COLUMN_NAME_PAYLOAD, message.serialize());
database.insert(TABLE_NAME, null, values);
}
}
});
database.close();
SendBird.addChannelHandler(UNIQUE_HANDLER_ID, new SendBird.ChannelHandler() {
@Override
public void onMessageReceived(BaseChannel baseChannel, BaseMessage baseMessage) {
if (baseChannel.getUrl().equals(mChannelUrl)) {
// Pass the message to your adapter.
mMessageListAdapter.addMessage(baseMessage);
// Store the message in your local database.
// It is a good idea to have a helper class or method for database transactions.
final SQLiteDatabase database = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_NAME_ID, baseMessage.getMessageId());
values.put(COLUMN_NAME_CHANNEL_URL, baseMessage.getChannelUrl());
values.put(COLUMN_NAME_TIMESTAMP, baseMessage.getCreatedAt());
values.put(COLUMN_NAME_PAYLOAD, baseMessage.serialize());
database.insert(TABLE_NAME, null, values);
database.close();
}
}
});
mChannel.sendUserMessage(MESSAGE_BODY, new BaseChannel.SendUserMessageHandler() {
@Override
public void onSent(UserMessage userMessage, SendBirdException e) {
if (e != null) {
// Handle error.
}
// Display sent message to RecyclerView.
mMessageListAdapter.addMessage(userMessage);
// Store the message in your local database.
// It is a good idea to have a helper class or method for database transactions.
final SQLiteDatabase database = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(COLUMN_NAME_ID, userMessage.getMessageId());
values.put(COLUMN_NAME_CHANNEL_URL, userMessage.getChannelUrl());
values.put(COLUMN_NAME_TIMESTAMP, userMessage.getCreatedAt());
values.put(COLUMN_NAME_PAYLOAD, userMessage.serialize());
database.insert(TABLE_NAME, null, values);
database.close();
}
});
Currently, it is difficult to sync deleted or edited messages. We are working to provide this feature in both our Chat SDKs and APIs, and hope to release it soon.
Save and load channels with serialization and deserialization
Your database should have a table to save and load channels, which has columns corresponding to the properties of a channel object.
Note: The following examples are based on a group channel. To cache an open channel, slightly improvise from the directions below (such as changing last_message_ts to channel_created_at).
After fetching new channels by using a OpenChannelListQuery or GroupChannelListQuery, serialize and insert each channel into your database. As with messages, we recommend storing the channel URL and timestamp of the last message in separate columns by using the channel.getUrl() and channel.getLastMessage().getCreatedAt(). This allows you to query the data on a row-by-row basis later on.
Before loading a list of channels, sort rows in the chronological order by last_message_ts. Then, deserialize each channel and display them in your UI.
Unlike messages, channels are relatively few in number and go through frequent property changes, such as cover URL and name changes, their deletions. We recommend updating a cache by completely replacing with new data when possible.
When real-time changes are made to a channel list, update your cache.
Note: In group channels, information associated with them can be updated or the current user might leave them anytime. To keep your local database synced with data in Sendbird server, your client app should check changes to the channels regularly and apply them to the database. You can retrieve change logs of the current user's group channels using getMyGroupChannelChangeLogsByToken() or getMyGroupChannelChangeLogsByTimestamp() method, with which you can manage your local database updates.
// Loading channels from your local database.
final SQLiteDatabase database = dbHelper.getWritableDatabase();
String sortOrder = COLUMN_NAME_LAST_MESSAGE_TIMESTAMP + " DESC";
Cursor cursor = database.query(
TABLE_NAME,
null, // The columns to return; all if null.
null, // The columns for the WHERE clause
null, // The values for the WHERE clause
null, // Don't group the rows.
null, // Don't filter by row groups.
sortOrder, // The sort order
"30" // The maximum number of returned results
);
// Create a list of `BaseChannel` objects by deserializing each.
final List<BaseChannel> prevChannelList = new ArrayList<>();
while (cursor.moveToNext()) {
byte[] data = cursor.getBlob(cursor.getColumnIndex(COLUMN_NAME_PAYLOAD));
BaseChannel channel = BaseChannel.buildFromSerializedData(data);
prevChannelList.add(channel);
}
cursor.close();
// Pass channels to adapter to display them in a RecyclerView, ListView, and so on.
mChannelListAdapter.addChannels(prevChannelList);
// Fetching new channels from Sendbird server.
GroupChannelListQuery listQuery = GroupChannel.createMyGroupChannelListQuery();
listQuery.next(new GroupChannelListQuery.GroupChannelListQueryResultHandler() {
@Override
public void onResult(List<GroupChannel> list, SendBirdException e) {
if (e != null) {
// Handle error.
}
// Replace the current (cached) dataset.
mChannelListAdapter.clear();
mChannelListAdapter.addChannels(prevChannelList);
// Clear the current cache.
database.delete(TABLE_NAME, null, null);
// Insert each new channel into your local database.
for (GroupChannel channel : list) {
// Store each new channel into the local database.
ContentValues values = new ContentValues();
values.put(COLUMN_NAME_CHANNEL_URL, channel.getUrl());
values.put(COLUMN_NAME_LAST_MESSAGE_TIMESTAMP, channel.getLastMessage().getCreatedAt());
values.put(COLUMN_NAME_PAYLOAD, channel.serialize());
database.insert(TABLE_NAME, null, values);
}
}
});
database.close();
}
SendBird.addChannelHandler(UNIQUE_HANDLER_ID, new SendBird.ChannelHandler() {
...
@Override
public void onChannelChanged(BaseChannel channel) {
final SQLiteDatabase database = dbHelper.getWritableDatabase();
String selection = COLUMN_NAME_CHANNEL_URL + " = ?";
String[] selectionArgs = { CURRENT_CHANNEL_URL };
// Get the changed channel from the local database using its URL.
Cursor cursor = database.query(
TABLE_NAME,
null, // The columns to return; all if null.
selection, // The columns for the WHERE clause
selectionArgs, // The values for the WHERE clause
null, // Don't group the rows.
null, // Don't filter by row groups.
null, // The sort order
"1" // The maximum number of returned resulting a channels
);
byte[] data = cursor.getBlob(cursor.getColumnIndex(COLUMN_NAME_PAYLOAD));
ContentValues values = new ContentValues();
values.put(COLUMN_NAME_CHANNEL_URL, channel.getUrl());
long lastMessageTs = ((GroupChannel) channel).getLastMessage().getCreatedAt();
values.put(COLUMN_NAME_LAST_MESSAGE_TIMESTAMP, lastMessageTs);
values.put(COLUMN_NAME_PAYLOAD, channel.serialize());
if (data != null) {
// If the channel is in the current cache, update it.
database.update(TABLE_NAME, values, selection, selectionArgs);
} else {
// If the channel is not currently cached, add it.
database.insert(TABLE_NAME, null, values);
}
database.close();
}
});
Note: A similar process can be applied to the onChannelDeleted(), onUserJoined(), and onUserLeft().