Android - Services

• A Service is an Android application component that performs long-running operations in the background without providing a user interface
• Services can be used for tasks like:
  • downloading files
  • playing music
  • or communicating with a remote server
• can continue working even after the user has left the app

Foreground Service

• Foreground services perform operations that require user attention
• They will provide users with notifications and continue running even when the app has no interaction or is minimized
• Foreground services must display notifications to inform the users that the service is running
• Examples of such services include media players and navigation apps
• A foreground service can be started by calling the startService() method.

Background Service

• Background services perform operations that do not require user interaction
• Starting with Android API level 26 (Android 8.0 Oreo) background services are no longer allowed to run unless the application is in the foreground
• This change was introduced to conserve system resources and optimize battery life.

Bound Service

• Bound services allow other application components to bind to them by calling the bindService() method
• They provide a client-server interface that enables components—even across different processes—to interact with the service using Inter Process Communication (IPC).
• Services extend the Service class.

public class ExampleService extends Service {
    int startMode;       // indicates how to behave if the service is killed
    IBinder binder;      // interface for clients that bind
    boolean allowRebind; // indicates whether onRebind should be used
    ...
    }
}

• Similar to activities

  • services have lifecycle callback methods that must be implemented to monitor changes in their state

• On the left

  • the service is created using startService()

• while on the right

  • the service is created using  bindService()

• Services must be declared in the AndroidManifest.xml file.

<manifest ...>
    <application ...>
        <service android:name=".MyForegroundService"/>
        <service android:name=".MyBackgroundService"/>
    </application>
</manifest>