androidx.activity

Kotlin |Java

Interfaces

A class that has an OnBackPressedDispatcher that allows you to register a OnBackPressedCallback for handling the system back button.

Classes

ComponentActivity	Base class for activities that enables composition of higher level components.
OnBackPressedCallback	Class for handling `OnBackPressedDispatcher#onBackPressed()` callbacks without strongly coupling that implementation to a subclass of `ComponentActivity`.
OnBackPressedDispatcher	Dispatcher that can be used to register `OnBackPressedCallback` instances for handling the `ComponentActivity#onBackPressed()` callback via composition.

Extension functions summary

For OnBackPressedDispatcher
OnBackPressedCallback	`OnBackPressedDispatcher.addCallback(owner: LifecycleOwner? = null, enabled: Boolean = true, onBackPressed: OnBackPressedCallback.() -> Unit)` Create and add a new OnBackPressedCallback that calls onBackPressed in OnBackPressedCallback.handleOnBackPressed.

For ComponentActivity
Lazy<VM>	`ComponentActivity.viewModels(noinline factoryProducer: () -> ViewModelProvider.Factory = null)` Returns a Lazy delegate to access the ComponentActivity's ViewModel, if factoryProducer is specified then ViewModelProvider.Factory returned by it will be used to create ViewModel first time.

Extension functions

addCallback

fun OnBackPressedDispatcher.addCallback(
    owner: LifecycleOwner? = null, 
    enabled: Boolean = true, 
    onBackPressed: OnBackPressedCallback.() -> Unit
): OnBackPressedCallback

Create and add a new OnBackPressedCallback that calls onBackPressed in OnBackPressedCallback.handleOnBackPressed.

If an owner is specified, the callback will only be added when the Lifecycle is androidx.lifecycle.Lifecycle.State.STARTED.

A default enabled state can be supplied.

viewModels

@MainThread inline fun <reified VM : ViewModel> ComponentActivity.viewModels(noinline factoryProducer: () -> ViewModelProvider.Factory = null): Lazy<VM>

Returns a Lazy delegate to access the ComponentActivity's ViewModel, if factoryProducer is specified then ViewModelProvider.Factory returned by it will be used to create ViewModel first time.

class MyComponentActivity : ComponentActivity() {
    val viewmodel: MyViewModel by viewmodels()
}

This property can be accessed only after the Activity is attached to the Application, and access prior to that will result in IllegalArgumentException.