Notification Channels

With Android Oreo, i.e. Android 8.0, Google introduced Notification Channels. You can get to know more about the UX in the Notifications UX talk at Google I/O 2017. For applications targeting API 26, i.e. Android 8.0, Google is enforcing every app to have a notification channel for their notifications. Without a notification channel, the applications notifications do not show up. For applications targeting < SDK 26, all notifications fall in the default notification channel, but the apps get to control the notification sound and vibration per notification.

Notification Channels

Notification channels provide a unified system to help users manage notifications. Notification channels allow you to create a user-customizable channel for each type of notification you want to display. Users can manage most of the settings associated with notifications using a consistent system UI. All notifications posted to the same notification channel have the same behavior. Users can visit Settings, or long-press a notification to change these behaviors, or even block a notification channel at any time.

Notification Groups

Notification channel groups allow you to manage multiple notification channels with identical names within a single app. 

Notification Badges

Notification badges show notifications associated with one or more notification channels in an app, which the user has not yet dismissed or acted on. Users can turn off badges for notification channels or apps from the Settings. User can dismiss/click these notification right from here.

How to use them

When we create a notification channel, we can set following properties which can't be updated once the channel has been submitted to the NotificationManager.

• Importance
• Notification Sound
• Vibration On/Off & Vibration Pattern
• Notification Icon
• Notification Group
• Ability to override 'Do-Not-Disturb' mode

You can't programmatically modify the behavior of a notification channel after it's created and submitted to the notification manager; the user is in charge of these settings after creation. We can rename a notification channel or update its description after creation.

Notification Group's description cannot be updated once they're created.

Importance Levels

Notification channels also allow us to preconfigure each channel with the types of alerts (Make sound, visual interruption, adding to notification shade).

Importance Level	Description
DEFAULT	Default notification importance: shows everywhere, makes noise, but does not visually intrude.
HIGH	Higher notification importance: shows everywhere, makes noise and peeks.
LOW	Low notification importance: shows everywhere, but is not intrusive.
MIN	Min notification importance: only shows in the shade, below the fold.

Regardless of the importance level we set per channel, the user can very well update these as per their liking. 

There are 3 more importance levels available, but they're not applicable as default values

• NONE - This notification doesn't show up at all.
• UNSPECIFIED - User hasn't set an importance
• MAX - Currently unused.

I have created a github project to test out all the various features of Notification channels. Do check it out.