OnBackInvokedDispatcher

Kotlin |Java

interface OnBackInvokedDispatcher

android.window.OnBackInvokedDispatcher

Dispatcher to register OnBackInvokedCallback instances for handling back invocations. It also provides interfaces to update the attributes of OnBackInvokedCallback. Attribute updates are proactively pushed to the window manager if they change the dispatch target (a.k.a. the callback to be invoked next), or its behavior.

Summary

Constants
static Int	`PRIORITY_DEFAULT` Default priority level of `OnBackInvokedCallback`s.
static Int	`PRIORITY_OVERLAY` Priority level of `OnBackInvokedCallback`s for overlays such as menus and navigation drawers that should receive back dispatch before non-overlays.
static Int	`PRIORITY_SYSTEM_NAVIGATION_OBSERVER` Priority level of `OnBackInvokedCallback`s designed to observe system-level back handling.

Public methods
abstract Unit	`registerOnBackInvokedCallback(priority: Int, callback: OnBackInvokedCallback)` Registers a `OnBackInvokedCallback`.
abstract Unit	`unregisterOnBackInvokedCallback(callback: OnBackInvokedCallback)` Unregisters a `OnBackInvokedCallback`.

Constants

PRIORITY_DEFAULT

Added in API level 33

static val PRIORITY_DEFAULT: Int

Default priority level of OnBackInvokedCallbacks.

Value: 0

PRIORITY_OVERLAY

Added in API level 33

static val PRIORITY_OVERLAY: Int

Priority level of OnBackInvokedCallbacks for overlays such as menus and navigation drawers that should receive back dispatch before non-overlays.

Value: 1000000

PRIORITY_SYSTEM_NAVIGATION_OBSERVER

Added in API level Baklava

static val PRIORITY_SYSTEM_NAVIGATION_OBSERVER: Int

Priority level of OnBackInvokedCallbacks designed to observe system-level back handling.

Callbacks registered with this priority do not consume back events. They receive back events whenever the system handles a back navigation and have no impact on the normal back navigation flow. Useful for logging or analytics.

Only one callback with PRIORITY_SYSTEM_NAVIGATION_OBSERVER can be registered at a time.

Value: -2

Public methods

registerOnBackInvokedCallback

Added in API level 33

abstract fun registerOnBackInvokedCallback(
    priority: Int, 
    callback: OnBackInvokedCallback
): Unit

Registers a OnBackInvokedCallback. Within the same priority level, callbacks are invoked in the reverse order in which they are registered. Higher priority callbacks are invoked before lower priority ones.

Parameters
`priority`	Int: The priority of the callback. Value is `android.window.OnBackInvokedDispatcher#PRIORITY_DEFAULT`, `android.window.OnBackInvokedDispatcher#PRIORITY_OVERLAY`, or `android.window.OnBackInvokedDispatcher#PRIORITY_SYSTEM_NAVIGATION_OBSERVER` Value is 0 or greater
`callback`	OnBackInvokedCallback: The callback to be registered. If the callback instance has been already registered, the existing instance (no matter its priority) will be unregistered and registered again. This value cannot be `null`.

Exceptions
`java.lang.IllegalArgumentException`	if the priority is negative.

unregisterOnBackInvokedCallback

Added in API level 33

abstract fun unregisterOnBackInvokedCallback(callback: OnBackInvokedCallback): Unit

Unregisters a OnBackInvokedCallback.

Parameters
`callback`	OnBackInvokedCallback: The callback to be unregistered. Does nothing if the callback has not been registered. This value cannot be `null`.