ComponentCallbacks2

Kotlin |Java

public interface ComponentCallbacks2
implements ComponentCallbacks

android.content.ComponentCallbacks2

Known indirect subclasses

AbstractInputMethodService, AccessibilityService, AccountAuthenticatorActivity, Activity, ActivityGroup, AliasActivity, AppFunctionService, Application, AutofillService, CallRedirectionService, CallScreeningService, CameraPrewarmService, CarrierMessagingClientService, CarrierMessagingService, CarrierService, and 60 others.

AbstractInputMethodService	AbstractInputMethodService provides a abstract base class for input methods.
AccessibilityService	Accessibility services should only be used to assist users with disabilities in using Android devices and apps.
AccountAuthenticatorActivity	This class was deprecated in API level 30. Applications should extend Activity themselves. This class is not compatible with AppCompat, and the functionality it provides is not complex.
Activity	An activity is a single, focused thing that the user can do.
ActivityGroup	This class was deprecated in API level 13. Use the new `Fragment` and `FragmentManager` APIs instead; these are also available on older platforms through the Android compatibility package.
AliasActivity	This class was deprecated in API level 30. Use `<activity-alias>` or subclass Activity directly.
AppFunctionService	Abstract base class to provide app functions to the system.
Application	Base class for maintaining global application state.
AutofillService	An `AutofillService` is a service used to automatically fill the contents of the screen on behalf of a given user - for more information about autofill, read Autofill Framework.
CallRedirectionService	This service can be implemented to interact between Telecom and its implementor for making outgoing call with optional redirection/cancellation purposes.
CallScreeningService	This service can be implemented by the default dialer (see `TelecomManager.getDefaultDialerPackage()`) or a third party app to allow or disallow incoming calls before they are shown to a user.
CameraPrewarmService	Extend this class to implement a camera prewarm service.
CarrierMessagingClientService	If the default SMS app has a service that extends this class, the system always tries to bind it so that the process is always running, which allows the app to have a persistent connection to the server.
CarrierMessagingService	A service that receives calls from the system when new SMS and MMS are sent or received.
CarrierService	A service that exposes carrier-specific functionality to the system.
ChooserTargetService	This class was deprecated in API level 30. For publishing direct share targets, please follow the instructions in https://developer.android.com/training/sharing/receive.html#providing-direct-share-targets instead.
CloudMediaProvider	Base class for a cloud media provider.
CompanionDeviceService	A service that receives calls from the system with device events.
ConditionProviderService	This class was deprecated in API level 29. Instead of using an automatically bound service, use `NotificationManager.setAutomaticZenRuleState(String, Condition)` to tell the system about the state of your rule. In order to maintain a link from Settings to your rule configuration screens, provide a configuration activity that handles `NotificationManager.ACTION_AUTOMATIC_ZEN_RULE` on your `AutomaticZenRule` via `AutomaticZenRule.setConfigurationActivity(ComponentName)`.
ConnectionService	An abstract service that should be implemented by any apps which either: Can make phone calls (VoIP or otherwise) and want those calls to be integrated into the built-in phone app.
ContentProvider	Content providers are one of the primary building blocks of Android applications, providing content to applications.
ControlsProviderService	Service implementation allowing applications to contribute controls to the System UI.
CredentialProviderService	Service to be extended by credential providers, in order to return user credentials to the framework.
DeviceAdminService	Base class for a service that device owner/profile owners can optionally have.
DialogFragment	This class was deprecated in API level 28. Use the Support Library `DialogFragment` for consistent behavior across all devices and access to Lifecycle.
DocumentsProvider	Base class for a document provider.
DreamService	Extend this class to implement a custom dream (available to the user as a "Daydream").
ExpandableListActivity	This class was deprecated in API level 30. Use `RecyclerView` or use `ExpandableListView` directly
Fragment	This class was deprecated in API level 28. Use the Jetpack Fragment Library `Fragment` for consistent behavior across all devices and access to Lifecycle.
HostApduService	HostApduService is a convenience `Service` class that can be extended to emulate an NFC card inside an Android service component.
HostNfcFService	HostNfcFService is a convenience `Service` class that can be extended to emulate an NFC-F card inside an Android service component.
InCallService	This service is implemented by an app that wishes to provide functionality for managing phone calls.
InputMethodService	InputMethodService provides a standard implementation of an InputMethod, which final implementations can derive from and customize.
IntentService	This class was deprecated in API level 30. IntentService is subject to all the background execution limits imposed with Android 8.0 (API level 26). Consider using `WorkManager` instead.
IsolatedService	Base class for services that are started by ODP on a call to `OnDevicePersonalizationManager#execute(ComponentName, PersistableBundle, java.util.concurrent.Executor, OutcomeReceiver)` and run in an isolated process.
JobService	Entry point for the callback from the `JobScheduler`.
LauncherActivity	This class was deprecated in API level 30. Applications can implement this UI themselves using `RecyclerView` and `PackageManager.queryIntentActivities(Intent, int)`
ListActivity	This class was deprecated in API level 30. Use `ListFragment` or `RecyclerView` to implement your Activity instead.
ListFragment	This class was deprecated in API level 28. Use the Support Library `ListFragment` for consistent behavior across all devices and access to Lifecycle.
MediaBrowserService	Base class for media browser services.
MediaRoute2ProviderService	Base class for media route provider services.
MediaSession2Service	This API is not generally intended for third party application developers.
MidiDeviceService	A service that implements a virtual MIDI device.
MidiUmpDeviceService	A service that implements a virtual MIDI device for Universal MIDI Packets (UMP).
MockApplication	This class was deprecated in API level 24. Use a mocking framework like Mockito. New tests should be written using the Android Testing Support Library.
MockContentProvider	Mock implementation of ContentProvider.
NativeActivity	Convenience for implementing an activity that will be implemented purely in native code.
NotificationListenerService	A service that receives calls from the system when new notifications are posted or removed, or their ranking changed.
OffHostApduService	OffHostApduService is a convenience `Service` class that can be extended to describe one or more NFC applications that are residing off-host, for example on an embedded secure element or a UICC.
PreferenceActivity	This class was deprecated in API level 29. Use the AndroidX Preference Library for consistent behavior across all devices. For more information on using the AndroidX Preference Library see Settings.
PreferenceFragment	This class was deprecated in API level 28. Use the AndroidX Preference Library for consistent behavior across all devices. For more information on using the AndroidX Preference Library see Settings.
PrintService	This is the base class for implementing print services.
QuickAccessWalletService	A `QuickAccessWalletService` provides a list of `WalletCard`s shown in the Quick Access Wallet.
RecognitionService	This class provides a base class for recognition service implementations.
RemoteViewsService	The service to be connected to for a remote adapter to request RemoteViews.
SearchRecentSuggestionsProvider	This superclass can be used to create a simple search suggestions provider for your application.
Service	A Service is an application component representing either an application's desire to perform a longer-running operation while not interacting with the user or to supply functionality for other applications to use.
SettingInjectorService	Dynamically specifies the summary (subtitle) and enabled status of a preference injected into the list of app settings displayed by the system settings app For use only by apps that are included in the system image, for preferences that affect multiple apps.
SettingsPreferenceService	Base class for a service that exposes its settings preferences to external access.
SliceProvider	This class was deprecated in API level 35. Slice framework has been deprecated, it will not receive any updates from `ERROR(/android.os.Build.VANILLA_ICE_CREAM)` and forward. If you are looking for a framework that sends displayable data from one app to another, consider using `AppSearchManager`.
SpellCheckerService	SpellCheckerService provides an abstract base class for a spell checker.
TabActivity	This class was deprecated in API level 13. New applications should use Fragments instead of this class; to continue to run on older devices, you can use the v4 support library which provides a version of the Fragment API that is compatible down to `Build.VERSION_CODES.DONUT`.
TextToSpeechService	Abstract base class for TTS engine implementations.
TileService	A TileService provides the user a tile that can be added to Quick Settings.
TvAdService	The TvAdService class represents a TV client-side advertisement service.
TvInputService	The TvInputService class represents a TV input or source such as HDMI or built-in tuner which provides pass-through video or broadcast TV programs.
TvInteractiveAppService	A TV interactive application service is a service that provides runtime environment and runs TV interactive applications.
VisualVoicemailService	This service is implemented by dialer apps that wishes to handle OMTP or similar visual voicemails.
VoiceInteractionService	Top-level service of the current global voice interactor, which is providing support for hotwording, the back-end of a `VoiceInteractor`, etc.
VoiceInteractionSession	An active voice interaction session, providing a facility for the implementation to interact with the user in the voice interaction layer.
VoiceInteractionSessionService	An active voice interaction session, initiated by a `VoiceInteractionService`.
VpnService	VpnService is a base class for applications to extend and build their own VPN solutions.
VrListenerService	A service that is bound from the system while running in virtual reality (VR) mode.
WallpaperService	A wallpaper service is responsible for showing a live wallpaper behind applications that would like to sit on top of it.
WebViewFragment	This class was deprecated in API level 28. Manually call `WebView.onPause()` and `WebView.onResume()`

Callbacks for app state transitions that can be used to improve background memory management. This interface is available in all application components (Activity, Service, ContentProvider, and Application).

You should implement onTrimMemory(int) to release memory when your app goes to background states. Doing so helps the system keep your app's process cached in memory for longer, such that the next time that the user brings your app to the foreground, the app will perform a warm or hot start, resuming faster and retaining state.

Trim memory levels and how to handle them

TRIM_MEMORY_UI_HIDDEN
Your app's UI is no longer visible. This is a good time to release large memory allocations that are used only by your UI, such as Bitmaps, or resources related to video playback or animations.
TRIM_MEMORY_BACKGROUND
Your app's process is considered to be in the background, and has become eligible to be killed in order to free memory for other processes. Releasing more memory will prolong the time that your process can remain cached in memory. An effective strategy is to release resources that can be re-built when the user returns to your app.

Apps that continue to do work for the user when they're not visible can respond to the TRIM_MEMORY_UI_HIDDEN callback by changing their behavior to favor lower memory usage. For example, a music player may keep full-sized album art for all tracks in the currently playing playlist as Bitmaps cached in memory. When the app is backgrounded but music playback continues, the app can change the caching behavior to cache fewer, or smaller, Bitmaps in memory.

The ordinal values for trim levels represent an escalating series of memory pressure events, with incrementing values accordingly. More states may be added in the future. As such, it's important not to check for specific values, but rather check if the level passed to onTrimMemory(int) is greater than or equal to the levels that your application handles. For example:

public void onTrimMemory(int level) {
     if (level >= TRIM_MEMORY_BACKGROUND) {
         // Release any resources that can be rebuilt
         // quickly when the app returns to the foreground
         releaseResources();
     } else if (level >= TRIM_MEMORY_UI_HIDDEN) {
         // Release UI-related resources
         releaseUiResources();
     }
 }

Note: the runtime may invoke Garbage Collection (GC) in response to application state changes. There is no need to explicitly invoke GC from your app.

Summary

Constants
`int`	`TRIM_MEMORY_BACKGROUND` Level for `onTrimMemory(int)`: the process has gone on to the LRU list.
`int`	`TRIM_MEMORY_COMPLETE` This constant was deprecated in API level 35. Apps are not notified of this level since API level 34
`int`	`TRIM_MEMORY_MODERATE` This constant was deprecated in API level 35. Apps are not notified of this level since API level 34
`int`	`TRIM_MEMORY_RUNNING_CRITICAL` This constant was deprecated in API level 35. Apps are not notified of this level since API level 34
`int`	`TRIM_MEMORY_RUNNING_LOW` This constant was deprecated in API level 35. Apps are not notified of this level since API level 34
`int`	`TRIM_MEMORY_RUNNING_MODERATE` This constant was deprecated in API level 35. Apps are not notified of this level since API level 34
`int`	`TRIM_MEMORY_UI_HIDDEN` Level for `onTrimMemory(int)`: the process had been showing a user interface, and is no longer doing so.

Public methods
`abstract void`	`onTrimMemory(int level)` Called when the operating system has determined that it is a good time for a process to trim unneeded memory from its process.

Inherited methods

From interface


        
          android.content.ComponentCallbacks

`abstract void`	`onConfigurationChanged(Configuration newConfig)` Called by the system when the device configuration changes while your component is running.
`abstract void`	`onLowMemory()` This method was deprecated in API level 35. Since API level 14 this is superseded by `ComponentCallbacks2.onTrimMemory`. Since API level 34 this is never called. If you're overriding ComponentCallbacks2#onTrimMemory and your minSdkVersion is greater than API 14, you can provide an empty implementation for this method.

Constants

TRIM_MEMORY_BACKGROUND

Added in API level 14

public static final int TRIM_MEMORY_BACKGROUND

Level for onTrimMemory(int): the process has gone on to the LRU list. This is a good opportunity to clean up resources that can efficiently and quickly be re-built if the user returns to the app.

Constant Value: 40 (0x00000028)