/

• English
• Deutsch
• Español – América Latina
• Français
• Indonesia
• Polski
• Português – Brasil
• Tiếng Việt
• 中文 – 简体
• 日本語
• 한국어

Android Studio Sign in

• API reference

ComponentCallbacks2

public interface ComponentCallbacks2
implements ComponentCallbacks

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.  PccService Abstract base class for a PCC service that receives data from other components.  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 WalletCards 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

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

public static final int TRIM_MEMORY_BACKGROUND

public static final int TRIM_MEMORY_COMPLETE

public static final int TRIM_MEMORY_MODERATE

public static final int TRIM_MEMORY_RUNNING_CRITICAL

public static final int TRIM_MEMORY_RUNNING_LOW

public static final int TRIM_MEMORY_RUNNING_MODERATE

public static final int TRIM_MEMORY_UI_HIDDEN

Public methods

onTrimMemory

public 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. You should never compare to exact values of the level, since new intermediate values may be added -- you will typically want to compare if the value is greater or equal to a level you are interested in.

To retrieve the processes current trim level at any point, you can use ActivityManager.getMyMemoryState(RunningAppProcessInfo).

• TRIM_MEMORY_COMPLETE
• TRIM_MEMORY_MODERATE
• TRIM_MEMORY_BACKGROUND
• TRIM_MEMORY_UI_HIDDEN
• TRIM_MEMORY_RUNNING_CRITICAL
• TRIM_MEMORY_RUNNING_LOW
• TRIM_MEMORY_RUNNING_MODERATE