Safe identifier for a window. This currently allows you to retrieve and observe the input focus state of the window. Most applications will not use this, instead relying on the simpler (and more efficient) methods available on Android.Views.View. This classes is useful when window input interactions need to be done across processes: the class itself is a Parcelable that can be passed to other processes for them to interact with your window, and it provides a limited safe API that doesn't allow the other process to negatively harm your window.

[Android Documentation]