Official Description: Android Support Leanback v17

CommonsWare’s Notes

The “leanback” classes provide the structure for a UI designed for use on televisions. A television UI frequently needs to be significantly different than one for a phone or tablet, owing to the greater distance to the screen and the use of some form of remote for interacting with the app. The “leanback” classes in this artifact provide the foundation for such a UI, based upon some of the original UI patterns for Google TV (the predecessor to Android TV).

As with many Jetpack libraries, the “leanback” code significantly pre-dates the Jetpack. If you see references to “v17” editions of this code (e.g., in packages), there will be many similarities with the current AndroidX code.