Added in API level 36

SystemOnBackInvokedCallbacks

class SystemOnBackInvokedCallbacks
kotlin.Any
   ↳ android.window.SystemOnBackInvokedCallbacks

Utility class providing OnBackInvokedCallbacks to override the default behavior when system back is invoked. e.g. Activity.finish

By registering these callbacks with the OnBackInvokedDispatcher, the system can trigger specific behaviors and play corresponding ahead-of-time animations when the back gesture is invoked.

For example, to trigger the Activity.moveTaskToBack behavior: 

OnBackInvokedDispatcher dispatcher = activity.getOnBackInvokedDispatcher();
    dispatcher.registerOnBackInvokedCallback(
        OnBackInvokedDispatcher.PRIORITY_DEFAULT,
        SystemOnBackInvokedCallbacks.moveTaskToBackCallback(activity));

Summary

Public methods
static OnBackInvokedCallback

Get a callback to triggers Activity.finishAndRemoveTask() on the associated Activity.
static OnBackInvokedCallback

Get a callback to triggers Activity.moveTaskToBack(boolean) on the associated Activity, moving the task containing the activity to the background.

Public methods

finishAndRemoveTaskCallback

Added in API level 36
static fun finishAndRemoveTaskCallback(activity: Activity): OnBackInvokedCallback

Get a callback to triggers Activity.finishAndRemoveTask() on the associated Activity. If the activity is the root activity of its task, the entire task will be removed from the recents task. The activity will be finished in all cases. The system will play the corresponding transition animation.

Parameters
activity Activity: The associated Activity This value cannot be null.
Return
OnBackInvokedCallback This value cannot be null.

moveTaskToBackCallback

Added in API level 36
static fun moveTaskToBackCallback(activity: Activity): OnBackInvokedCallback

Get a callback to triggers Activity.moveTaskToBack(boolean) on the associated Activity, moving the task containing the activity to the background. The system will play the corresponding transition animation, regardless of whether the activity is the root activity of the task.

Parameters
activity Activity: The associated Activity This value cannot be null.
Return
OnBackInvokedCallback This value cannot be null.