Delivery receipt

Delivery receipt is a feature that indicates whether a message has successfully been delivered to all the intended recipients by Sendbird server. With the implementation of delivery receipt, Sendbird not only provides the timestamp of when each user has last read the messages in each channel, but also the timestamp of when each user has the message last delivered to each user in each channel.

Note: Delivery receipt is only applicable to group channels.

Delivery receipt provides the following benefits.

Most popular messaging apps, such as WhatsApp and Facebook Messenger, provide this feature. Users who have experienced them expect to see if the message they sent has been successfully delivered when using a new chat service. Delivery receipt is a feature in high demand that today’s users are accustomed to using.

Previously, a sender had no way of knowing whether their message was unread because the server is in the process of delivering or failed to deliver the message due to the unreliable internet connection, or simply because the recipients haven’t yet read the message. This feature enables users to become better-informed, thus improving the Sendbird user experience.

Delivery receipt works in a similar way to read receipt. The server stores the timestamp of the message last delivered as delivered_ts. The timestamp is recorded per user, per channel.

Each SDK provides methods to make the Chat API's mark all messages as delivered action calls. If required, each SDK also makes necessary changes to handle the new response key, delivery_receipt, for APIs that return a group channel resource.

When a user sends a message to a group channel by calling the SDK’s sendUserMessage() method, it is considered a delivery event for Sendbird server.

Note: To implement delivery receipt notifications in an Android chat app, see this tutorial.

To mark messages as delivered when a group channel member receives a push notification for the message from FCM, either the SendBird.markAsDelivered() static method or the groupChannel.markAsDelivered() instance method should be called.

public class FirebaseMessagingServiceEx extends FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        // Implement the following.
        SendBird.markAsDelivered(remoteMessage.getData());
    }
}

When a message is delivered to group channel members who are online, it is automatically marked as delivered and the members are notified of delivery receipt through the onDeliveryReceiptUpdated() method in the channel event handler. However, when the message is delivered as a push notification to group channel members who are offline, the message can be marked as delivered through the groupChannel.markAsDelivered().

SendBird.addChannelHandler(UNIQUE_HANDLER_ID, new SendBird.ChannelHandler() {
    @Override
    public void onMessageReceived(BaseChannel baseChannel, BaseMessage baseMessage) {
        ...
    }

    @Override
    public void onDeliveryReceiptUpdated(GroupChannel channel) {
        ...
    }
});

You can retrieve the number of members who haven’t received a specific message in a group channel. If zero is returned, it means that the message has been delivered to all the other members.

SendBird.addChannelHandler(UNIQUE_HANDLER_ID, new SendBird.ChannelHandler() {
    @Override
    public void onMessageReceived(BaseChannel baseChannel, BaseMessage baseMessage) {
        ...
    }

    @Override
    public void onDeliveryReceiptUpdated(GroupChannel channel) {
        Boolean isAllDelivered = channel.getUndeliveredMemberCount(MESSAGE) == 0;

        ...
    }
});