Implement Default and Custom Notification Channels
By default, Android Oreo and the SDK sends all notifications on a default channel using a user-specified name:
All push messages sent use only this channel. You do not need to specify the channel used to send messages with this option, as the SDK only sends using the default channel.
You can also create custom channels used for sending notifications with different settings:
Override the SDK channel callback to assign a given message to a channel. Ensure you include a channel with your message. Otherwise, the app does not display the message to the recipient.
You can customize channel priority, colors, and sounds. Each channel requires its own sound configuration. Otherwise, custom sounds do not work. You cannot use sounds with the SDK default channel option.