Question

it is possible to have an activity without UI to performaction

Answer 1

Short answer: Yes — but an Activity is normally a UI component, so it's better to use a Service/WorkManager for background work. If you really need an Activity without visible UI you can create one with no UI (Theme.NoDisplay) and do your work in onCreate/onResume then finish().

Details and options

1) Activity with no UI (Theme.NoDisplay)
- Add a theme so no window is shown:
- Manifest: android:theme="@android:style/Theme.NoDisplay"
- In the Activity do the work and call finish() immediately.

Example (Java):
- Manifest:
<activity android:name=".NoUiActivity"
android:theme="@android:style/Theme.NoDisplay" />

- Activity:
public class NoUiActivity extends Activity {
@Override protected void onCreate(Bundle s) {
super.onCreate(s);
// perform short action (synchronously or start a background thread)
doAction();
finish(); // close immediately
}
}

Notes:
- This is suitable for very short tasks that need an Activity context (e.g., launching an Intent that requires an Activity).
- You may still briefly switch tasks; Theme.NoDisplay prevents a visible layout but you may see a context switch.

2) Prefer Services / WorkManager for background work
- For short background work started by your app, use WorkManager or JobScheduler (for API level constraints).
- For immediate background processing use a Service (or JobIntentService / foreground service for long-running work).
Examples:
- WorkManager (recommended for deferrable/reliable work):
WorkManager.getInstance(context).enqueue(new OneTimeWorkRequest.Builder(MyWorker.class).build());
- Service: startService(intent) or startForegroundService for long-running foreground work.

Why Services/WorkManager are usually better
- Activities are intended for UI. Background tasks are more correctly handled with Services/WorkManager.
- Android places restrictions on starting Activities from background (Android 10+). If your app might be in background, starting an Activity without UI may fail or be disallowed — better to use a Service/notification flow.

If you tell me what action you need to perform (short/long running, must run when app is backgrounded, needs UI permissions, etc.), I can suggest the best component and give sample code (Kotlin or Java).