Sender side for getting an update for messages that are marked as delivered.

SenderDeliveryReceipt.java

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

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

    }
});